Since June 2024, CDC’s Advisory Committee on Immunization Practices (ACIP) has recommended a single dose of RSV vaccination for all adults aged ≥75 years and for adults aged 60–74 years who are at increased risk of severe RSV disease. RSV vaccines are effective in preventing RSV-associated hospitalization, with the potential to prevent tens of thousands of annual hospitalizations and deaths in older adults. However, certain adults aged < 60 years are also at increased risk of severe illness caused by RSV. In considering RSV vaccination for adults aged 50–59 years, ACIP reviewed risk of RSV-associated hospitalization among adults with and without chronic medical conditions, differential risk by race and ethnicity, duration of vaccine protection and potential need for revaccination, risk of Guillain-Barre syndrome (GBS) associated with subunit RSV vaccines, national vaccine uptake, societal costs of the vaccination program, complexity of changes to the immunization schedule, and challenges in implementing a risk-based recommendation in retail pharmacies, where most older adults have received RSV vaccination. ACIP members discussed variability in individual-level risk of severe RSV disease in persons with specific chronic conditions and the balance of benefits and risks of RSV vaccination in adults aged < 60 years, who generally experience lower risk of severe outcomes from RSV infection compared with older adults. Members were concerned about the disproportionate burden of severe RSV disease and higher prevalence of chronic medical conditions among Black adults in the U.S., particularly in the 50–59-year age group. Members expressed a need for more data to inform optimal timing of revaccination after vaccine-induced immunity wanes, which is particularly important for younger adults with longer remaining life expectancy. Overall, Committee members thought that the public health benefits of RSV vaccination outweighed risks for adults aged 50–59 years with certain chronic medical conditions. On April 16, 2025, ACIP recommended a single dose of RSV vaccine for these adults using the same qualifying risk conditions used for adults aged 60–74 years. ACIP plans to consider RSV vaccine recommendations for adults aged 18–49 years at a future public meeting. Helen Y. Chu, MD, MPH, Roche: Advisor/Consultant|Vir: Advisor/Consultant

On June 26, 2024, the CDC updated respiratory syncytial virus (RSV) vaccine recommendations to a single dose of RSV vaccine for all adults aged ≥ 75 years and adults aged 60-74 years with increased risk of severe RSV disease. Using electronic health record (EHR) data from the VISION platform, we described characteristics of patients testing negative for RSV who did and did not receive an RSV vaccine and assessed factors associated with RSV vaccine receipt.Figure 1:Characteristics associated with receipt of respiratory syncytial virus (RSV) vaccination among test-negative patients with an emergency department (ED) encounter for RSV-like illness (RLI) during the 2024-2025 season in the VISION network, N=23,403 patientsFigure 2:Characteristics associated with receipt of respiratory syncytial virus (RSV) vaccine among test-negative patients with an inpatient encounter for RSV-like illness (RLI) during the 2024-2025 season in the VISION network, N=25,020 patients Patients with ≥ 1 emergency department (ED) or inpatient encounter at any of 6 participating health systems in 8 states with RSV-like illness (RLI) during October 1, 2024-March 31, 2025 were included. Vaccination status was ascertained from EHR, state and city immunization information systems, and medical claims. Patients who tested positive for SARS-CoV-2 or influenza viruses at the same RLI encounter were excluded. Patient age, sex, race and ethnicity, Medicaid status, number of underlying medical conditions, month of medical encounter, and documented receipt of COVID-19 or influenza vaccines were evaluated as covariates when assessing the odds of vaccination. The best fitting multivariable logistic regression models using Bayesian Information Criterion were chosen. Among 48423 included patients, 2113 (4.4%) had documented RSV vaccine receipt. The odds of RSV vaccination differed by site and increased with calendar time and age. Compared to patients aged 60-64 years, those aged ≥ 75 years were more likely to have received an RSV vaccine (ED: aOR: 3.6, 95%CI: 2.7-4.8, Figure 1; inpatient: aOR: 2.3, 95%CI: 1.7-3.0, Figure 2). Receipt of both influenza and COVID-19 vaccine within the same season had the strongest association with RSV vaccination in both the ED (aOR: 14.88, 95%CI: 11.87-18.89, Figure 1) and hospital setting (aOR: 20.04, 95%CI: 16.20-25.03, Figure 2). Receipt of other respiratory viral vaccines was the strongest indicator of RSV vaccination in the 2024-2025 RSV season in patients testing negative for RSV among all demographic and clinical characteristics considered. RSV vaccination was lower among those aged 60-64 years than older patients. These findings inform future methods to estimate vaccine effectiveness and inform policy implementation. Gabriela Vazquez-Benitez, PhD, MSc, AbbVie: research funding not related to this study|Sanofi: Grant funding for other research not related to this study Stephanie Irving, MHS, Westat: Grant/Research Support Nicola P. Klein, MD, PhD, AstraZeneca: Grant/Research Support|Centers for Disease Control and Prevention: Grant/Research Support|GlaxoSmithKline: Grant/Research Support|Janssen: Grant/Research Support|Merck: Grant/Research Support|Moderna: Grant/Research Support|Pfizer: Grant/Research Support|Sanofi Pasteur: Grant/Research Support|Seqirus: Grant/Research Support Shaun J. Grannis, MD, MS, Centers for Disease Control and Prevention: Grant/Research Support|National Institutes of Health NCATS: Grant/Research Support|National Institutes of Health NIMH: Grant/Research Support Toan Ong, PhD, Centers for Disease Control and Prevention via Westat: Grant/Research Support|Patent Title: Systems and Methods For Record Linkage: Patent Number: PCT/US2018/047961|PCORI: Travel Support|Regenstrief Institute: Advisor/Consultant|Regenstrief Institute: Travel Support Sarah W. Ball, MPH, ScD, Centers for Disease Control and Prevention, Contract #200-2019-F-06819: Grant/Research Support|Centers for Disease Control and Prevention, Contract #75D30121D12779: Grant/Research Support|Novavax: Grant/Research Support Jingran Cao, MS, Sanofi Pasteur: Grant/Research Support Charlene E. McEvoy, MD, MPH, Astra Zeneca: Grant/Research Support|Centers for Disease Control and Prevention: Grant/Research Support|Department of Defense: Grant/Research Support|GlaxoSmithKline: Grant/Research Support|National Institutes of Health: Grant/Research Support|PCORI: Grant/Research Support Ousseny Zerbo, PhD, Centers for Disease Control and Prevention: Grant/Research Support|Moderna: Grant/Research Support|National Institutes of Health: Grant/Research Support|Pfizer: Grant/Research Support John R. Hansen, MPH, Centers for Disease Control and Prevention: Grant/Research Support Lawrence Block, MPH, MPA, Centers for Disease Control and Prevention: Grant/Research Support Karen B. Jacobson, MD, MPH, Centers for Disease Control and Prevention: Grant/Research Support|National Institutes of Health: Grant/Research Support|Pfizer: Grant/Research Support William F. Fadel, PhD, Centers for Disease Control and Prevention: Grant/Research Support Catia Chavez, MPH, Westat: Grant/Research Support Karthik Natarajan, PhD, Centers for Disease Control and Prevention: Grant/Research Support Ryan E. Wiegand, PhD, Merck & Co., Inc.: Stocks/Bonds (Public Company)|Sanofi S.A.: Stocks/Bonds (Public Company)

Respiratory syncytial virus (RSV) causes substantial morbidity and mortality in older adults. In June 2023, CDC’s Advisory Committee on Immunization Practices recommended adults aged ≥60 years receive one RSV vaccine dose under shared clinical decision making. The recommendation was updated in June 2024 as follows: adults aged ≥75 years and adults aged 60–74 years at increased risk for severe RSV disease are recommended to receive one RSV vaccine dose. Monitoring RSV vaccine uptake informs vaccine effectiveness studies and the impact of updated vaccine recommendations.Figure 1:Biweekly cumulative RSV vaccination coverage, by age group, community-dwelling Medicare Fee-For-Service beneficiaries aged ≥65 Years and enrolled in a Part D plan, United StatesFee-for-Service: enrolled in Medicare Parts A/B (and not Part C) for 365 days prior to reporting period.*6-week reporting lag; data may be incomplete after December 7, 2024.Figure 2:Biweekly cumulative RSV vaccination coverage, by underlying medical condition*, Community-dwelling Medicare Fee-for-Service beneficiaries aged ≥65 years and enrolled in Part D plan, United StatesFee-for-Service: enrolled in Medicare Parts A/B for 365 days prior to reporting period.* Conditions included lung disease, hematologic disease, cardiovascular disease, diabetes associated with organ damage, liver disease, obesity, neurologic disease, end stage kidney disease, and immunocompromising conditions. Presence of underlying medical condition (other than immunocompromising conditions) was defined as ≥1 claim in prior 365 days listing ICD-10 diagnosis code corresponding to condition. Presence of immunocompromising condition was defined as ≥2 encounters in prior 183 days with a diagnosis code. Immunocompromising conditions included hematologic malignancy, solid malignancy, transplant, rheumatologic/inflammatory conditions, other intrinsic immune conditions, or HIV. End stage kidney disease was defined as ≥1 claim for dialysis encounter in prior 90 days (excluding acute kidney injury). | †6-week reporting lag; data may be incomplete after December 7, 2024. RSV vaccine uptake was assessed in biweekly periods during June 2023 through January 2025. All Medicare beneficiaries aged ≥65 years, enrolled in Medicare Part D since June 21, 2023, through the last Saturday of a biweekly period, and continuously enrolled in Parts A and B in the 365 days prior to the first day of a biweekly period were included. Vaccination status was determined through Medicare Part D. Beneficiaries who received an RSV vaccine prior to June 21, 2023, were excluded. Vaccine uptake was assessed by age group, nursing home residence, and underlying medical condition (UMC) status.Figure 3:Biweekly cumulative RSV vaccination coverage, by community-dwelling or nursing home-dwelling Medicare Fee-for-Service beneficiaries aged ≥65 years and enrolled in Part D plan, United StatesFee-for-Service: enrolled in Medicare Parts A/B for 365 days prior to reporting period.*6-week reporting lag; data may be incomplete after December 7, 2024. | †Regardless of age or underlying medical condition status. An average of 16,176,382 Medicare Fee-For-Service beneficiaries were included in each biweekly period. RSV vaccine uptake sharply increased during June 2023 to January 2024 (19%); uptake was slower during June 2024 to January 2025 (5%) (Figure 1). By January 5–18, 2025, 27% of eligible beneficiaries had received the RSV vaccine. Uptake was higher among those aged ≥75 years (31%) compared to those aged 65-74 years old (24%). RSV vaccine uptake varied by UMC category, with beneficiaries with lung disease having the highest uptake (34%) and beneficiaries with end stage kidney disease having the lowest uptake (18%) (Figure 2). RSV vaccination coverage was consistently lower among nursing home residents compared with community-dwelling beneficiaries (Figure 3). RSV vaccine uptake among Medicare Fee-For-Service beneficiaries aged ≥65 years was modest after updated RSV vaccine recommendations. Differences in RSV vaccine uptake were observed by age group, nursing home residence, and UMCs. Ryan E. Wiegand, PhD, Merck & Co., Inc.: Stocks/Bonds (Public Company)|Sanofi S.A.: Stocks/Bonds (Public Company)

IMPORTANCE An estimated 1% to 3% of children with SARS-CoV-2 infection will develop post- COVID-19 condition (PCC). OBJECTIVE To evaluate the odds of PCC among children with COVID-19 vaccination prior to SARSCoV-2 infection compared with odds among unvaccinated children. DESIGN, SETTING, AND PARTICIPANTS In this case-control study, children were enrolled in a multisite longitudinal pediatric cohort from July 27, 2021, to September 1, 2022, and followed up through May 2023. Analysis used a case (PCC reported)-control (no PCC reported) design and included children aged 5 to 17 years whose first real time-polymerase chain reaction (RT-PCR)- confirmed SARS-CoV-2 infection occurred during the study period, who were COVID-19 vaccine age-eligible at the time of infection, and who completed a PCC survey at least 60 days after infection. From December 1, 2022, to May 31, 2023, children had weekly SARS-CoV-2 testing and were surveyed regarding PCC (>= 1 new or ongoing symptom lasting >= 1 month after infection). EXPOSURES COVID-19 mRNA vaccination status at time of infection was the exposure of interest; participants were categorized as vaccinated (>= 2-dose series completed >= 14 days before infection) or unvaccinated. Vaccination status was verified through vaccination cards or vaccine registry and/or medical records when available. MAIN OUTCOME AND MEASURES Main outcomes were estimates of the odds of PCC symptoms. Multivariate logistic regression was performed to estimate the odds of PCC among vaccinated children compared with odds of PCC among unvaccinated children. RESULTS A total of 622 participants were included, with 28 (5%) case participants and 594(95%) control participants. Median (IQR) age was 10.0 (7.0-11.9) years for case participants and 10.3 (7.8-12.7) years for control participants (P = .37). Approximately half of both groups reported female sex (13 case participants [46%] and 287 control participants [48%]). Overall, 57% of case participants (16 children) and 77% of control participants (458 children) were vaccinated (P = .05). After adjusting for demographic characteristics, number of acute COVID-19 symptoms, and baseline health, COVID-19 vaccination was associated with decreased odds of 1 or more PCC symptom (adjusted odds ratio [aOR], 0.43; 95% CI, 0.19-0.98) and 2 or more PCC symptoms (aOR, 0.27; 95% CI, 0.10-0.69). CONCLUSIONS AND RELEVANCE In this study, mRNA COVID-19 vaccination was associated with reduced odds of PCC in children. The aORs correspond to an estimated 57% and 73% reduced likelihood of 1 or more and 2 or more PCC symptoms, respectively, among vaccinated vs unvaccinated children. These findings suggest benefits of COVID-19 vaccination beyond those associated with protection against acute COVID-19 and may encourage increased pediatric uptake.

Abstract Background Several COVID-19 vaccine safety and effectiveness studies have used real-world data (RWD), including health insurance claims to delineate people’s vaccination history. However, COVID-19 vaccine administration is not completely captured in claims because vaccines administered in some settings, such as mass vaccination centers, do not generate insurance claims. Failure to capture complete vaccination history in claims data may result in misclassification of vaccination status leading to biased effectiveness and safety estimates. As part of a study to evaluate COVID-19 vaccine effectiveness in pregnant persons, we examined how linking claims with Immunization Information System (IIS) records improves vaccination record capture for pregnant people.Figure 1:Vaccination capture in claims and IIS Methods We identified individuals in a large commercial claims database who were pregnant between 12/11/2020 and 7/31/2023 and resided in 21 jurisdictions for which we had permission to use IIS data for public health purposes. We linked COVID-19 vaccination records from IIS and insurance claims and calculated the percentage of records that were captured in IIS only, claims only, and in both. We also compared COVID-19 vaccination capture in claims and IIS over time to assess how the completeness of IIS and claims data have changed over time. Results This study included 101,355 pregnant people, of which 13% (12,726) had ≥1 COVID-19 vaccination record only in IIS, 18% (17,787) had ≥1 vaccination record only in the claims data, and 36% (36,209) had vaccination records in both (Figure 1). Approximately 34% (34,633) did not have a vaccination record in IIS or claims. Over time, the percentages of individuals with vaccination records in IIS, claims, and both changed; the temporal patterns aligned with a shift from vaccinations at mass vaccination centers to pharmacies and clinics. Conclusion This study demonstrates the importance of integrating data from multiple RWD sources to capture vaccine history for vaccine effectiveness studies in pregnant people and the general population. Relying on only one data source may result in substantial misclassification of vaccinated individuals as unvaccinated, leading to biased results. Disclosures Alexandra Stone, PhD, United Health Group: Stocks/Bonds (Public Company) Wafa Tarazi, PhD, MHPA, UnitedHealth Group: I am an employee at UHG Nwanneamaka Ume, MPH, Optum: I am an Employee of Optum, a UnitedHealth Group subsidiary Andrea Steffens, MPH, OPTUM: Employee|UnitedHealth Group: Stocks/Bonds (Public Company) Katherine Andrade, MPH, Optum: Employee|United Health Group: Stocks/Bonds (Public Company) Garrett Gremel, MS, Optum: Employee Ami R. Buikema, MPH, Optum: Employee|UnitedHealth Group: Stocks/Bonds (Public Company) Wenya Grace Yang, MPA, MA, UnitedHealth Group: I am an employee of UHG.|UnitedHealth Group: Stocks/Bonds (Public Company)

BACKGROUND:Previous estimates of vaccine effectiveness (VE) against asymptomatic influenza virus infection based on seroconversion have varied widely and may be biased. We estimated 2022-2023 influenza VE against illness and asymptomatic infection in a prospective cohort. METHODS:In the HEROES-RECOVER cohort, adults at increased occupational risk of influenza exposure across 7 US sites provided weekly symptom reports and nasal swabs for reverse transcription-polymerase chain reaction (RT-PCR) influenza testing. Laboratory-confirmed influenza virus infections were classified as symptomatic (≥1 symptom) or asymptomatic during the week of testing. Participants reported demographic information and vaccination through surveys; most sites verified vaccination through medical record and immunization registry review. Person-time was calculated as days from the site-specific influenza season start (September-October 2022) through date of infection, study withdrawal, or season end (May 2023). We compared influenza incidence among vaccinated versus unvaccinated participants overall, by symptom status, and by influenza A subtype, using Cox proportional hazards regression adjusted for site and occupation. We estimated VE as (1 - adjusted hazard ratio) × 100%. RESULTS:In total, 269 of 3785 (7.1%) participants had laboratory-confirmed influenza, including 263 (98%) influenza A virus infections and 201 (75%) symptomatic illnesses. Incidence of laboratory-confirmed influenza illness among vaccinated versus unvaccinated participants was 23.7 and 33.2 episodes per 100 000 person-days, respectively (VE: 38%; 95% CI: 15%-55%). Incidence of asymptomatic influenza virus infection was 8.0 versus 11.6 per 100 000 (VE: 13%; 95% CI: -47%, 49%). CONCLUSIONS:Vaccination reduced incidence of symptomatic but not asymptomatic influenza virus infection, suggesting that influenza vaccination attenuates progression from infection to illness.

During 2023, the Centers for Disease Control and Prevention (CDC) recommended the first respiratory syncytial virus (RSV) immunizations intended for widespread use in the United States to prevent severe RSV illness in infants and older adults. CDC, in collaboration with federal, public health, and academic partners, is conducting evaluations of real-world effectiveness of recommended RSV immunization products in the United States. Similar frameworks for evaluation are being applied to RSV vaccines and nirsevimab, a long-acting preventative monoclonal antibody, to estimate product effectiveness. The overall goal of CDC's RSV immunization effectiveness program is to generate timely and robust evidence through observational studies to inform immunization product policy decisions and other measures related to RSV prevention and control. CDC is evaluating effectiveness through high-quality, well-controlled observational studies leveraging a variety of platforms that provide robust data to inform policy decisions.

Few type-specific antibodies that recognize drifted epitopes are made during post-vaccination exposures to SARS-CoV-2 variants1–12, perhaps due to suppression by previous immunity. We compared type-specific B cell responses in unvaccinated and vaccinated individuals with Delta and Omicron BA.1 SARS-CoV-2 variant infections. For both Delta, which is antigenically similar to the vaccine strain, and the more distant BA.1 variant, neutralizing antibodies were greater in post-vaccination variant infections than in primary variant infections. Delta type-specific memory B cells were reduced in post-vaccination Delta infections relative to primary variant infections. Yet some drifted epitopes in the Delta variant elicited minimal responses even in primary infections. For BA.1 infections, type-specific antibodies and memory B cells were mostly undetectable, irrespective of previous immunity. Thus, poor intrinsic antigenicity of drifted epitopes in Delta and BA.1 infections superseded the impact of previous immunity. Enhancing the immunogenicity of vaccine antigens may promote type-specific responses. Bhattacharya and colleagues assess the impact of antigenic imprinting using samples from mRNA vaccinated or unvaccinated individuals primarily infected with the SARS-CoV-2 variants Delta and Omicron BA.1.

To understand how coronavirus disease 2019 vaccines impact infection risk in children <5 years, we assessed risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection from September 2022 to April 2023 in 3 cohort studies. There was no difference in risk by vaccination status. While vaccines reduce severe disease, they may not reduce SARS-CoV-2 infections in naïve young children.

Abstract Background Pregnant people with COVID-19 are at higher risk of severe illness, pregnancy complications, and adverse pregnancy outcomes. While maternal COVID-19 vaccination has been shown to be safe and effective for pregnant people and their infants, vaccine coverage rates during pregnancy are not optimal. Additional data on the receipt and distribution of COVID-19 vaccine prior to and during pregnancy can inform efforts to increase coverage. We describe COVID-19 vaccination patterns and timing of the most recent vaccine dose among pregnant people.Figure 1.Distribution of COVID-19 Vaccination Patterns Prior to and During Pregnancy among Privately Insured Pregnant Persons, December 2020 - July 2023Notes: In 25,890 pregnancy episodes, the most recent COVID-19 vaccination was received during pregnancy and vaccinations were approximately evenly distributed across trimesters. In the remaining 16,647 episodes, the most recent vaccination was received before the start of pregnancy with almost half of the vaccinations occurring 3-6 months before pregnancy. Methods Vaccination data from a large national commercial claims database were supplemented with data from 21 Immunization Information Systems for which we have permission to use data. We calculated the percentage of pregnant people ages 18-55 years identified between June 2020 and July 2023 who received a COVID-19 vaccination between December 2020 and July 2023. We describe timing of most recent dose received in the 6 months prior to pregnancy (3-6 months, 1-3 months, < 1 month before last menstrual period [LMP]) and during pregnancy, by trimester (first, second, third trimester). Results This study included a total of 120,633 pregnancies among 102,311 pregnant people (mean age at LMP = 32 years; standard deviation: 5). About a third (35.3%, n = 42,537) received ≥1 COVID-19 vaccine dose within the 6 months prior to or during pregnancy; of those, 39.1% received ≥1 dose prior to pregnancy, 41.6% received ≥1 dose during pregnancy, and 19.3% received doses both before and during pregnancy. Among those who received the vaccine before pregnancy, 45.8% received the most recent dose 3-6 months, 34.8% 1-3 months, and 19.4% < 1 month before LMP. Receipt of the most recent COVID-19 vaccine dose during pregnancy was distributed almost evenly across the first (30.5%), second (34.9%), and third (34.6%) trimesters. Conclusion This study found that approximately one third of pregnancies included people who were vaccinated with at least 1 dose of COVID-19 vaccine during pregnancy or within 6 months prior to LMP. The most recent dose was not received more frequently at any time before or during pregnancy. Understanding COVID-19 vaccination patterns and timing is important to assess adherence to vaccination recommendations among this high-risk population. Disclosures Wafa Tarazi, PhD, MHPA, UnitedHealth Group: I am an employee at UHG alexandra stone, PhD, United Health Group: Stocks/Bonds (Public Company) Nwanneamaka Ume, MPH, Optum: I am an Employee of Optum, a UnitedHealth Group subsidiary Andrea Steffens, MPH, OPTUM: Employee|UnitedHealth Group: Stocks/Bonds (Public Company) Katherine Andrade, MPH, Optum: Employee|United Health Group: Stocks/Bonds (Public Company) Garrett Gremel, MS, Optum: Employee Ami R. Buikema, MPH, Optum: Employee|UnitedHealth Group: Stocks/Bonds (Public Company) Wenya Grace Yang, MPA, MA, UnitedHealth Group: I am an employee of UHG.|UnitedHealth Group: Stocks/Bonds (Public Company)

On September 12, 2023, the Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices recommended that all persons aged ≥6 months receive 2023-2024 COVID-19 vaccination. This study examines the relationship between vaccination and COVID-19 symptom frequency, using data from the Increasing Community Access to Testing, Treatment, and Response (ICATT) platform. Among 6966 records of first SARS-CoV-2-positive tests collected from September 21, 2023 through August 22, 2024, individuals who received 2023-2024 COVID-19 vaccination consistently reported lower frequencies of 12 symptoms. The adjusted odds of reporting most symptoms were significantly lower among vaccinated participants, especially recent loss of sense of smell or taste (adjusted odds ratio(aOR): 0.39; 95 %CI: 0.29-0.53) and muscle pain (aOR: 0.49; 95 %CI: 0.41-0.59). These findings indicate that receiving 2023-2024 COVID-19 vaccination was associated with significantly lower odds of reporting most COVID-19 symptoms following SARS-CoV-2 infection, highlighting the importance of receiving recommended COVID-19 vaccination to mitigate symptomatic illness.

The extent to which semi-quantitative antibody levels confer protection against SARS-CoV-2 infection in populations with heterogenous immune histories is unclear. Two nested case-control studies were designed within the multisite HEROES/RECOVER prospective cohort of frontline workers to study the relationship between antibody levels and protection against first-time post-vaccination infection and reinfection with SARS-CoV-2 from December 2021 to January 2023. All participants submitted weekly nasal swabs for rRT-PCR testing and blood samples quarterly and following infection or vaccination. Cases of first-time post-vaccination infection following a third dose of monovalent (origin strain WA-1) mRNA vaccine (n = 613) and reinfection (n = 350) were 1:1 matched to controls based on timing of blood draw and other potential confounders. Conditional logistic regression models were fit to estimate infection risk reductions associated with 3-fold increases in end titers for receptor binding domain (RBD). In first-time post-vaccination and reinfection study samples, most were female (67%, 57%), non-Hispanic (82%, 68%), and without chronic conditions (65%, 65%). The odds of first-time post-vaccination infection were reduced by 21% (aOR = 0.79, 95% CI = [0.66-0.96]) for each 3-fold increase in RBD end titers. The odds of reinfection associated with a 3-fold increase in RBD end titers were reduced by 23% (aOR = 0.77, 95% CI = [0.65-0.92] for unvaccinated individuals and 58% (aOR = 0.42, 95% CI = [0.22-0.84]) for individuals with three mRNA vaccine doses following their first infection. Frontline workers with higher antibody levels following a third dose of mRNA COVID-19 vaccine were at reduced risk of SARS-CoV-2 during Omicron predominance. Among those with previous infections, the point estimates of risk reduction associated with antibody levels was greater for those with three vaccine doses compared to those who were unvaccinated.

Respiratory syncytial virus (RSV) is a major cause of respiratory illness and hospitalization in older adults during fall and winter in the United States. The 2023-2024 RSV season was the first during which RSV vaccination was recommended for U.S. adults aged ≥60 years, using shared clinical decision-making. On June 26, 2024, the Advisory Committee on Immunization Practices voted to update this recommendation as follows: a single dose of any Food and Drug Administration-approved RSV vaccine (Arexvy [GSK]; Abrysvo [Pfizer]; or mResvia [Moderna]) is now recommended for all adults aged ≥75 years and for adults aged 60-74 years who are at increased risk for severe RSV disease. Adults who have previously received RSV vaccine should not receive another dose. This report summarizes the evidence considered for these updated recommendations, including postlicensure data on vaccine effectiveness and safety, and provides clinical guidance for the use of RSV vaccines in adults aged ≥60 years. These updated recommendations are intended to maximize RSV vaccination coverage among persons most likely to benefit, by clarifying who is at highest risk and by reducing implementation barriers associated with the previous shared clinical decision-making recommendation. Continued postlicensure monitoring will guide future recommendations.

Respiratory syncytial virus (RSV) causes substantial morbidity and mortality in older adults. In May 2023, two subunit RSV vaccines (Arexvy [GSK] and Abrysvo [Pfizer]) received approval from the U.S. Food and Drug Administration (FDA). In June 2023, ACIP recommended that adults aged ≥60 years may receive a single dose of RSV vaccine, using shared clinical decision-making. In support of development of this policy, our objective was to assess the cost-effectiveness of RSV vaccination in the general population in this age group. We used a decision-analytical model of RSV over a two-year timeframe using data from published literature, FDA documents, epidemiological databases, and manufacturer data. We tracked RSV-associated outpatient, emergency department, inpatient healthcare utilization, RSV-attributable deaths, quality-adjusted life-years lost (QALYs), and societal costs. The societal cost per QALY saved from RSV vaccination depended on age group and product: adults aged ≥60 years, $196,842 for GSK's vaccine and $176,557 for Pfizer's vaccine; adults ≥65 years, $162,138 for GSK and $146,543 for Pfizer; adults 60- <65 years, $385,829 for GSK and $331,486 for Pfizer. Vaccine efficacy, incidence of RSV hospitalization, and vaccine cost had the greatest influence on cost per QALY. Cost per QALY saved decreased as the age of those vaccinated increased. Inputs such as long-term efficacy are uncertain. RSV vaccination in adults aged ≥60 years may be cost-effective, particularly in those of more advanced age. Lower vaccine acquisition costs and persistent efficacy beyond two RSV seasons would render RSV vaccination more cost-effective for a broader target population. Primary Funding Source US Centers for Disease Control and Prevention.

BACKGROUND:On September 2, 2022, bivalent COVID-19 mRNA vaccines, were recommended to address reduced effectiveness of COVID-19 monovalent vaccines during SARS-CoV-2 Omicron variant predominance. METHODS:Using national pharmacy-based SARS-CoV-2 testing program data from January 15 to September 11, 2023, this test-negative, case-control design study assessed bivalent COVID-19 vaccine effectiveness (VE) against symptomatic infection. RESULTS:VE against symptomatic infection of a bivalent dose between 2 weeks and 1 month after bivalent vaccination ranged from 46% (95% CI: 38%-52%) for those aged ≥ 65 years to 61% (95% CI 41%-75%) for those aged 12-17 years. CONCLUSION:Bivalent vaccines protected against symptomatic infection. However, effectiveness waned over time, emphasizing the need to stay up to date with COVID-19 vaccination.

Importance Bivalent mRNA COVID-19 vaccines were recommended in the US for children and adolescents aged 12 years or older on September 1, 2022, and for children aged 5 to 11 years on October 12, 2022; however, data demonstrating the effectiveness of bivalent COVID-19 vaccines are limited. Objective To assess the effectiveness of bivalent COVID-19 vaccines against SARS-CoV-2 infection and symptomatic COVID-19 among children and adolescents. Design, Setting, and Participants Data for the period September 4, 2022, to January 31, 2023, were combined from 3 prospective US cohort studies (6 sites total) and used to estimate COVID-19 vaccine effectiveness among children and adolescents aged 5 to 17 years. A total of 2959 participants completed periodic surveys (demographics, household characteristics, chronic medical conditions, and COVID-19 symptoms) and submitted weekly self-collected nasal swabs (irrespective of symptoms); participants submitted additional nasal swabs at the onset of any symptoms. Exposure Vaccination status was captured from the periodic surveys and supplemented with data from state immunization information systems and electronic medical records. Main Outcome and Measures Respiratory swabs were tested for the presence of the SARS-CoV-2 virus using reverse transcriptase-polymerase chain reaction. SARS-CoV-2 infection was defined as a positive test regardless of symptoms. Symptomatic COVID-19 was defined as a positive test and 2 or more COVID-19 symptoms within 7 days of specimen collection. Cox proportional hazards models were used to estimate hazard ratios for SARS-CoV-2 infection and symptomatic COVID-19 among participants who received a bivalent COVID-19 vaccine dose vs participants who received no vaccine or monovalent vaccine doses only. Models were adjusted for age, sex, race, ethnicity, underlying health conditions, prior SARS-CoV-2 infection status, geographic site, proportion of circulating variants by site, and local virus prevalence. Results Of the 2959 participants (47.8% were female; median age, 10.6 years [IQR, 8.0-13.2 years]; 64.6% were non-Hispanic White) included in this analysis, 25.4% received a bivalent COVID-19 vaccine dose. During the study period, 426 participants (14.4%) had laboratory-confirmed SARS-CoV-2 infection. Among these 426 participants, 184 (43.2%) had symptomatic COVID-19, 383 (89.9%) were not vaccinated or had received only monovalent COVID-19 vaccine doses (1.38 SARS-CoV-2 infections per 1000 person-days), and 43 (10.1%) had received a bivalent COVID-19 vaccine dose (0.84 SARS-CoV-2 infections per 1000 person-days). Bivalent vaccine effectiveness against SARS-CoV-2 infection was 54.0% (95% CI, 36.6%-69.1%) and vaccine effectiveness against symptomatic COVID-19 was 49.4% (95% CI, 22.2%-70.7%). The median observation time after vaccination was 276 days (IQR, 142-350 days) for participants who received only monovalent COVID-19 vaccine doses vs 50 days (IQR, 27-74 days) for those who received a bivalent COVID-19 vaccine dose. Conclusion and Relevance The bivalent COVID-19 vaccines protected children and adolescents against SARS-CoV-2 infection and symptomatic COVID-19. These data demonstrate the benefit of COVID-19 vaccine in children and adolescents. All eligible children and adolescents should remain up to date with recommended COVID-19 vaccinations.

Background There are limited data on whether hybrid immunity differs by count and order of immunity-conferring events (infection with severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2] or vaccination against coronavirus disease 2019 [COVID-19]). From a multi-site cohort of frontline workers, we examined the heterogeneity of the effect of hybrid immunity on SARS-CoV-2 antibody levels.Methods Exposures included event count and event order, categorized into 7 permutations. Outcome was level of serum antibodies against receptor-binding domain (RBD) of the ancestral SARS-CoV-2 spike protein (total RBD-binding immunoglobulin). Means were examined up to 365 days after each of the first to seventh events.Results Analysis included 5793 participants measured from 7 August 2020 to 15 April 2023. Hybrid immunity from infection before 1 or 2 vaccine doses elicited modestly superior antibody responses after the second and third events (compared with infections or vaccine doses alone). This superiority was not repeated after additional events. Among adults infected before vaccination, adjusted geometric mean ratios (95% confidence interval [CI]) of anti-RBD early response (versus vaccinated only) were 1.23 (1.14-1.33), 1.09 (1.03-1.14), 0.87 (.81-.94), and 0.99 (.85-1.15) after the second to fifth events, respectively. Post-vaccination infections elicited superior responses; adjusted geometric mean ratios (95% CI) of anti-RBD early response (versus vaccinated only) were 0.93 (.75-1.17), 1.11 (1.06-1.16), 1.17 (1.11-1.24), and 1.20 (1.07-1.34) after the second to fifth events, respectively.Conclusions Evidence of heterogeneity in antibody levels by permutations of infection and vaccination history could inform COVID-19 vaccination policy. In this adult cohort, hybrid immunity elicited superior SARS-CoV-2 serum antibody response compared with COVID-19 vaccination alone; however, this superiority was not repeated after >= 4 immunizing events. Associations differed by permutations of immunizing events. These findings could inform vaccination strategies.

In May 2023, the Food and Drug Administration (FDA) licensed Arexvy and Abrysvo vaccines for prevention of respiratory syncytial virus (RSV) lower respiratory tract disease in adults aged >= 60 years. In prelicensure trials, Guillain-Barr & eacute; syndrome (GBS) was identified as a potential safety concern. During August 4, 2023-March 30, 2024, at least 10.6 million adults aged >= 60 years received a recommended RSV vaccine. During May 3, 2023-April 14, 2024, CDC reviewed data reported after RSV vaccination to V -safe, an active U.S. surveillance system that invites enrolled participants to complete web -based surveys, and reports to the Vaccine Adverse Event Reporting System (VAERS), a passive, voluntary surveillance system that accepts adverse event reports from the public, providers, and manufacturers. Findings from V -safe and VAERS were generally consistent with those from trials. Reporting rates of GBS after RSV vaccination in VAERS (5.0 and 1.5 reports per million doses of Abrysvo and Arexvy vaccine administered, respectively) were higher than estimated expected background rates in a vaccinated population. CDC and FDA are conducting population -based surveillance to assess risks for GBS and other adverse events. Findings from these studies will help guide development of Advisory Committee on Immunization Practices recommendations.

On September 12, 2023, CDC's Advisory Committee on Immunization Practices recommended updated 2023-2024 (updated) COVID-19 vaccination with a monovalent XBB.1.5-derived vaccine for all persons aged ≥6 months to prevent COVID-19, including severe disease. During fall 2023, XBB lineages co-circulated with JN.1, an Omicron BA.2.86 lineage that emerged in September 2023. These variants have amino acid substitutions that might increase escape from neutralizing antibodies. XBB lineages predominated through December 2023, when JN.1 became predominant in the United States. Reduction or failure of spike gene (S-gene) amplification (i.e., S-gene target failure [SGTF]) in real-time reverse transcription-polymerase chain reaction testing is a time-dependent, proxy indicator of JN.1 infection. Data from the Increasing Community Access to Testing SARS-CoV-2 pharmacy testing program were analyzed to estimate updated COVID-19 vaccine effectiveness (VE) (i.e., receipt versus no receipt of updated vaccination) against symptomatic SARS-CoV-2 infection, including by SGTF result. Among 9,222 total eligible tests, overall VE among adults aged ≥18 years was 54% (95% CI = 46%-60%) at a median of 52 days after vaccination. Among 2,199 tests performed at a laboratory with SGTF testing, VE 60-119 days after vaccination was 49% (95% CI = 19%-68%) among tests exhibiting SGTF and 60% (95% CI = 35%-75%) among tests without SGTF. Updated COVID-19 vaccines provide protection against symptomatic infection, including against currently circulating lineages. CDC will continue monitoring VE, including for expected waning and against severe disease. All persons aged ≥6 months should receive an updated COVID-19 vaccine dose.

Background. Data are limited on whether vaccination reduces post COVID conditions (PCCs) risk after less severe nonhospitalized coronavirus disease 2019 (COVID-19). This study assessed whether COVID-19 vaccination protected against PCCs in persons with mild initial infections during Delta and Omicron variant predominance. Methods. This study utilized a case-control design, nested within the HEROES-RECOVER cohort. Participants aged >= 18 years with test-confirmed severe acute respiratory syndrome coronavirus disease 2 (SARS-CoV-2) between 28 June 2021 and 14 September 2022 were surveyed for PCCs, defined by symptoms lasting >4 weeks after initial infection. Cases self-reported PCCs and controls self-reported no PCCs. The exposure was messenger RNA (mRNA) COVID-19 vaccination (2 or 3 monovalent doses). Odds of PCCs among vaccinated and unvaccinated persons were compared with logistic regression. Results. Of 936 participants, 23.6% reported PCCs and 83.2% were vaccinated. Participants who received 3 vaccine doses had lower odds of PCC-related gastrointestinal, neurological, and other symptoms compared to unvaccinated participants (adjusted odds ratio [95% confidence interval]: 0.37 [.16-.85], 0.56 [.32-.97], and 0.48 [.25-.91], respectively). Conclusions. COVID-19 vaccination protected against development of PCCs among persons with mild infection during both Delta and Omicron variant predominance, supporting vaccination as an important PCCs prevention tool.