OBJECTIVES:To investigate vaccination coverage for influenza and COVID-19 in the SARS-CoV-2 immunity and reinfection evaluation (SIREN) study cohort of healthcare workers (HCWs) between 2020 and 2023 and explore vaccination enablers and barriers. DESIGN:A mixed-methods study nested within SIREN, a multicentre prospective cohort study of HCWs across the UK. Quantitative and qualitative methods were used sequentially, using an expansion/explanation function, enabling emergent themes observed from the quantitative stage to be explored in the qualitative stage. SETTING:SIREN sites include secondary care centres and community mental health trusts in the UK. PARTICIPANTS:Quantitative analysis was conducted on data from 6048 participants. Participants were representative of the HCW workforce, with the majority being women (83%) and of white ethnicity (88%). Nurses made up the largest occupational group (33%). Qualitative analysis of data from 24 participants including five focus groups (n=21) and three semistructured interviews (n=3); 82% women, 26% minority ethnic, all working age from across the UK. PRIMARY OUTCOME MEASURES:Quantitative: vaccine coverage for COVID-19 and influenza vaccines by demographic with multivariable logistical regression used to assess differences. Qualitative: thematic analysis to explore reasons behind the results seen in the quantitative stage. RESULTS:COVID-19 vaccination was initially high; 97% received two doses and 94% a first booster. However, coverage was reduced to 77%, for the second booster. Influenza vaccination coverage was lowest in 2020-2021 (46%), increasing to 73% in 2021-2022 and to 79% in 2022-2023. In 2022-2023, vaccination coverage was higher for influenza than for COVID-19. High vaccine coverage for both COVID-19 and influenza was observed in doctors, pharmacists and therapists. Porters, healthcare assistants and staff from minority ethnic groups had lower vaccine coverage for both COVID-19 and influenza. Four themes were identified: (1) attitudes towards vaccination changed throughout the COVID-19 pandemic; (2) HCWs used data to inform vaccination decisions; (3) poor communication in healthcare settings contributed to a reduction in vaccination; (4) there were both positive and negative impacts of the COVID-19 vaccine on influenza vaccine uptake and other vaccination programmes. CONCLUSIONS:Between 2020 and 2023 in our cohort, COVID-19 vaccination coverage decreased, whereas influenza increased. Our study found attitudes to both vaccines have shifted, becoming more favourable to influenza and less to COVID-19 boosters. Barriers to COVID-19 boosters, including concerns about side effects and vaccine effectiveness, need to be addressed with improved communication on the benefits and adverse events. Future vaccination strategies should address the differences we have identified in vaccine coverage across demographics and occupational groups, including continued efforts to improve vaccine equity. TRIAL REGISTRATION NUMBER:ISRCTN11041050.

INTRODUCTION:The combination of patient illness and staff absence driven by seasonal viruses culminates in annual "winter pressures" on UK healthcare systems and has been exacerbated by COVID-19. In winter 2022/23 we introduce multiplex testing aiming to determine the incidence of SARS-CoV-2, influenza and respiratory syncytial virus (RSV) in our cohort of UK healthcare workers (HCWs). METHODS:The pilot study was conducted from 28/11/2022-31/03/2023 within the SIREN prospective cohort study. Participants completed fortnightly questionnaires, capturing symptoms and sick leave, and multiplex PCR testing for SARS-CoV-2, influenza and RSV, regardless of symptoms. PCR-positivity rates by virus were calculated over time, and viruses were compared by symptoms and severity. Self-reported symptoms and associated sick leave were described. Sick leave rates were compared by vaccination status and demographics. RESULTS:5,863 participants were included, 84.6% female, 70.3% ≥ 45-years, 91.4% of White ethnicity and 82.6% in a patient facing role. PCR-positivity peaked in early December for all three viruses (4.6 positives per 100 tests (95%CI 3.5, 5.7) SARS-CoV-2, 3.9 (95%CI 2.2, 5.6) influenza, 1.4 (95%CI 0.4, 2.4) RSV), declining to <0.3/100 tests after January for influenza/RSV, and around 2.5/100 tests for SARS-CoV-2. Over one-third of all infections were asymptomatic, and symptoms were similar for all viruses. 1,368 (23.3%) participants reported taking sick leave, median 4 days (range 1-59). Rates of sick leave were higher in participants with co-morbidities, working in clinical settings, and who had not been vaccinated (COVID-19 booster or seasonal influenza vaccine) versus those who had received neither vaccine (2.04 vs 1.41 sick days/100 days, adjusted Incidence Rate Ratio 1.47 (95%CI 1.38, 1.56). CONCLUSION:This pilot demonstrated the use of multiplex testing allowed better understanding of the impact of seasonal respiratory viruses and respective vaccines on the HCW workforce. This highlights the important information on asymptomatic infection and persisting levels of SARS-CoV-2 infection.

OBJECTIVES:The SARS-CoV-2 Immunity and Reinfection Evaluation (SIREN) study is a prospective multicentre cohort study established to evaluate the immune response to SARS-CoV-2 following infection and vaccination in UK healthcare workers. The aim of this study is to explore barriers and facilitators experienced by SIREN sites to set-up and run the study, and implications for future research within NHS systems. STUDY DESIGN:Qualitative study. METHODS:Seven focus groups (n = 33) and three one-to-one semi-structured interviews (n = 3) were conducted via MS Teams with SIREN site teams and SIREN participants. RESULTS:A thematic analysis indicates a decentralised model, multidisciplinary team working, pre-existing networks, visible senior support, diverse recruitment methods, and co-design methods contributed to the success of SIREN. Barriers to setting up SIREN sites included limited experience of running a large-scale study, lack of processes and resources, and limited organisational support. Providing SIREN sites with the flexibility to develop models of practice that consider the local context worked well. More centralised support including documents, templates and provision for peer support and shared learning can lower the administrative burden of local site teams. CONCLUSIONS:Participation in the SIREN study has strengthened the research infrastructure of local sites and promoted more collaborative research processes which should be maintained to address future challenges at pace within NHS systems.

BACKGROUND:SIREN is a healthcare worker cohort study aiming to determine COVID-19 incidence, duration of immunity and vaccine effectiveness across 135 NHS organisations in four UK nations. Conducting an intensive prospective cohort study during a pandemic was challenging. We designed an evolving retention programme, informed by emerging evidence on best practice. This included applying a multifactorial approach, and considering strategies for barrier reduction, community building, follow-up, and tracing. We utilised participant engagement tools underpinned by our Participant Involvement Panel (PIP) and here we evaluate cohort retention over time and identify learnings. METHODS:A mixed method evaluation of cohort retention in 12 and 24-month follow-up (June 2020 - March 2023). We described cohort retention by demographics and site, using odds ratios from logistic regression. Withdrawal reasons during this time were collected by survey. We collected participant feedback via cross-sectional online survey conducted October - November 2022, utilising a behavioural science approach. We conducted two focus groups with research teams in February 2023 and conducted thematic analysis exploring cohort retention challenges and facilitators. RESULTS:37,275 (84.7%) participants completed 12-months of follow-up. Of 14,772 participants extending their follow-up to 24 months, 12,635 (85.5%) completed this. Retention increased with age in the 12 (55-64 years vs < 25 years OR = 2.50; 95% CI: 2.19-2.85; p < 0.001) and 24-month (> 65 years vs < 25 years OR = 2.92; 95% CI: 1.78-4.88; p < 0.001) cohorts. Retention was highest in the Asian and Black ethnic groups compared to White in the 12 (OR = 1.38; 95% CI: 1.23-1.56; p < 0.001, and OR = 1.64; 95% CI: 1.30-2.08; p < 0.001) and 24-month (OR = 1.78; 95% CI: 1.42-2.25; p < 0.001, and OR = 2.12; 95% CI: 1.41-3.35; p < 0.001) cohort. Among participants withdrawing, the median time in follow-up at withdrawal was 7 months (IQR: 4-10 months) within the 12-month cohort and 19 months within the 24-month cohort (IQR: 16-22 months). The top three reasons for participant withdrawal were workload, leaving site employment and medical reasons. Themes identified from focus-groups included: the need to monitor and understand participant motivation over time, the necessity of inclusive and comprehensive communication, the importance of acknowledging participant contributions, building collaboration with local research teams, and investing in the research team skillset. CONCLUSION:Participant retention in the SIREN study remained high over 24-months of intensive follow-up, demonstrating that large cohort studies are feasible as a pandemic research tool. Our evaluation suggests it is possible to maintain an engaged cohort of healthcare workers (HCWs) during an acute pandemic response phase. The insights gained from this population group are important, as a highly exposed group fulfilling an essential pandemic response and patient care function. The success of the cohort study overall, as well as the specific population group retained, offer useful insight for pandemic preparedness planning and healthcare worker studies.

Introduction During the COVID-19 pandemic, extensive research was conducted on SARS-CoV-2; however, important questions about other respiratory pathogens remain unanswered. A severe influenza season in 2022–2023 with simultaneous circulation of SARS-CoV2 and respiratory syncytial virus is anticipated. This sub-study aims to determine the incidence and impact of these respiratory viruses on healthcare workers, the symptoms they experienced, the effectiveness of both COVID-19 and influenza vaccination and the burden of these infections on the National Health Service (NHS) workforce. Methods and analysis This is a longitudinal prospective cohort sub-study, utilising the population and infrastructure of the SARS-CoV-2 Immunity & Reinfection Evaluation (SIREN) study, which focuses on hospital staff in the UK. Participants undergo fortnightly nucleic acid amplification testing on a multiplex assay including SARS-CoV-2, influenza A and B and RSV, regardless of symptoms. Questionnaires are completed every two weeks, capturing symptoms, sick days, exposures, and vaccination records. Serum samples are collected monthly or quarterly from participants associated with a SIREN site. This sub-study commenced on 28/11/22 to align with the predicted influenza season and participants’ influenza vaccine status. The SIREN Participant Involvement Panel shaped the aims and methods for the study, highlighting its acceptability. UK devolved administrations were supported to develop local protocols. Analysis plans include incidence of asymptomatic and symptomatic infection, comparisons of vaccination coverage, assessment of sick day burden, and effectiveness of seasonal influenza against infection and time off work. Data are also integrated into UKHSA nosocomial modelling. Ethics and dissemination The protocol was approved by the Berkshire Research Ethics Committee (IRAS ID 284460, REC Reference 20SC0230) on 14/11/2022. Participants were informed in advance. As the frequency and method of sampling remained the same, implied consent processes were approved by the committee. Participants returning to the study give informed consent. Regular reports to advisory groups and peer-reviewed publications are planned to disseminate findings and inform decision making. Clinical trial registration number: ISRCTN11041050; registration date: 12 January 2021. Sub study included in protocol version: v8.0, and amended in v9.0

BACKGROUND:Rapid timescales for the design and delivery of research were common during the COVID-19 pandemic. The recruitment and retention of healthcare workers (HCWs) as participants in research studies are notoriously challenging, but this was exacerbated during the pandemic by the unprecedented demand placed on the workforce. The SARS-CoV-2 Immunity and Reinfection Evaluation (SIREN study) is a prospective multicentre cohort study following HCWs in the UK. This paper discusses the strategies and challenges associated with recruitment and retention of HCW participants in Scotland. METHODS:There were 44,546 HCWs recruited to the SIREN study, of whom 6,285 were recruited by research teams at ten different research sites in Scotland between October 2020 and March 2021. Information on target and actual sample size, availability of resource, recruitment rate, and recruitment and engagement strategies by site was collated from SIREN study documentation and discussions with local key SIREN site staff. Individual-level data from 6,153 HCW participants with ongoing consent for all data usage were also collated, including socio-demographic data and information on withdrawal (in first year) and opt-in to a study extension after one year. Factors associated with these outcomes were explored in logistic regression analyses. RESULTS:Different recruitment strategies were used in each site according to local agreements, protocol and staff capacity, with the recruitment period ranging from 13 to 160 days. The locally-agreed recruitment target was met in four sites. The proportion of participants who withdrew in the first year ranged from 3.1 to 24.8% by site, while subsequent opt-in to a 12-month study extension ranged from 28.6 to 74.8%. The sites with the highest proportions of withdrawals were the same four sites with lowest proportions of opt-in. On an individual level, there was a lower level of retention among younger participants, and those from lower socio-economic backgrounds and minority ethnic groups. CONCLUSIONS:Site-specific factors including research-readiness likely had a significant influence on recruitment and retention, more so than the specific recruitment or retention strategies employed. Independent of site factors, individual-level variables influenced recruitment and retention, suggesting targeted strategies may be needed to promote research engagement among particular socio-demographic groups.

Introduction During the COVID-19 pandemic, extensive research was conducted on SARS-CoV-2; however, important questions about other respiratory pathogens remain unanswered. A severe influenza season in 2022–2023 with simultaneous circulation of SARS-CoV2 and respiratory syncytial virus is anticipated. This sub-study aims to determine the incidence and impact of these respiratory viruses on healthcare workers, the symptoms they experienced, the effectiveness of both COVID-19 and influenza vaccination and the burden of these infections on the National Health Service (NHS) workforce. Methods and analysis This is a longitudinal prospective cohort sub-study, utilising the population and infrastructure of the SARS-CoV-2 Immunity & Reinfection Evaluation (SIREN) study, which focuses on hospital staff in the UK. Participants undergo fortnightly nucleic acid amplification testing on a multiplex assay including SARS-CoV-2, influenza A and B and RSV, regardless of symptoms. Questionnaires are completed every two weeks, capturing symptoms, sick days, exposures, and vaccination records. Serum samples are collected monthly or quarterly from participants associated with a SIREN site. This sub-study commenced on 28/11/22 to align with the predicted influenza season and participants’ influenza vaccine status. The SIREN Participant Involvement Panel shaped the aims and methods for the study, highlighting its acceptability. UK devolved administrations were supported to develop local protocols. Analysis plans include incidence of asymptomatic and symptomatic infection, comparisons of vaccination coverage, assessment of sick day burden, and effectiveness of seasonal influenza against infection and time off work. Data are also integrated into UKHSA nosocomial modelling. Ethics and dissemination The protocol was approved by the Berkshire Research Ethics Committee (IRAS ID 284460, REC Reference 20SC0230) on 14/11/2022. Participants were informed in advance. As the frequency and method of sampling remained the same, implied consent processes were approved by the committee. Participants returning to the study give informed consent. Regular reports to advisory groups and peer-reviewed publications are planned to disseminate findings and inform decision making. Clinical trial registration number: ISRCTN11041050; registration date: 12 January 2021. Sub study included in protocol version: v8.0, and amended in v9.0

Since June 2020, the SARS-CoV-2 Immunity and Reinfection Evaluation (SIREN) study has conducted routine PCR testing in UK healthcare workers and sequenced PCR-positive samples. SIREN detected increases in infections and reinfections and delected Omicron subvariant waves emergence contemporaneous with national surveillance. SIREN's sentinel surveillance methods can be used for variant surveillance.

Background Participant involvement in research studies is not a new concept, yet barriers to implementation remain and application varies. This is particularly true for pandemic response research studies, where timeframes are condensed, pressure is high and the value and inclusion of participant involvement can be overlooked. The SIREN Participant Involvement Panel (PIP) provides a case study for participant involvement in pandemic research, working in partnership with people who the research is for and about. Methods SIREN and the British Society for Immunology (BSI) recruited and ran two phases of the PIP, involving 15 members in total over a 16-month period. Phase 1 ran between January and August 2022 and Phase 2 between October 2022 and March 2023. Activity figures including recruitment interest and PIP meeting attendance were recorded. To evaluate how the PIP has influenced SIREN, feedback was collected from (a) researchers presenting at the PIP and (b) PIP members themselves. Evaluation at the end of Phase 1 informed our approach to Phase 2. Thematic grouping was planned to identify key lessons learned. Results Applications increased from n = 30 to n = 485 between Phase 1 and Phase 2 of the PIP, a more than 15-fold increase. The SIREN PIP positively impacted the design, implementation and evaluation phases of the study and sub-studies. Feedback from PIP members themselves was positive, with members highlighting that they found the role rewarding and felt valued. Learnings from the PIP have been condensed into five key themes for applying to future pandemic response research studies: the importance of dedicated resources; recruiting the right panel; understanding motivations for participant involvement; providing flexible options for involvement and enabling the early involvement of participants. Conclusions The SIREN PIP has demonstrated the value of actively involving people who research is for and about. The PIP has provided an active feedback mechanism for research and demonstrated a positive influence on both SIREN study researchers and PIP members themselves. This paper makes the case for participant involvement in future pandemic research studies. Future work should include improved training for researchers and we would support the development of a national PIP forum as part of future pandemic research preparedness.

Background The protection of fourth dose mRNA vaccination against SARS-CoV-2 is relevant to current global policy decisions regarding ongoing booster roll-out. We estimate the effect of fourth dose vaccination, prior infection, and duration of PCR positivity in a highly-vaccinated and largely prior-COVID-19 infected cohort of UK healthcare workers. Methods Participants underwent fortnightly PCR and regular antibody testing for SARS-CoV-2 and completed symptoms questionnaires. A multi-state model was used to estimate vaccine effectiveness (VE) against infection from a fourth dose compared to a waned third dose, with protection from prior infection and duration of PCR positivity jointly estimated. Results 1,298 infections were detected among 9,560 individuals under active follow-up between September 2022 and March 2023. Compared to a waned third dose, fourth dose VE was 13.1% (95%CI 0.9 to 23.8) overall; 24.0% (95%CI 8.5 to 36.8) in the first two months post-vaccination, reducing to 10.3% (95%CI - 11.4 to 27.8) and 1.7% (95%CI -17.0 to 17.4) at 2-4 and 4-6 months, respectively. Relative to an infection >2 years ago and controlling for vaccination, 63.6% (95%CI 46.9 to 75.0) and 29.1% (95%CI 3.8 to 43.1) greater protection against infection was estimated for an infection within the past 0-6, and 6-12 months, respectively. A fourth dose was associated with greater protection against asymptomatic infection than symptomatic infection, whilst prior infection independently provided more protection against symptomatic infection, particularly if the infection had occurred within the previous 6 months. Duration of PCR positivity was significantly lower for asymptomatic compared to symptomatic infection. Conclusions Despite rapid waning of protection, vaccine boosters remain an important tool in responding to the dynamic COVID-19 landscape; boosting population immunity in advance of periods of anticipated pressure, such as surging infection rates or emerging variants of concern. Funding UK Health Security Agency, Medical Research Council, NIHR HPRU Oxford, and others.