INTRODUCTION:Understanding the impact of public health and social measures (PHSMs) on influenza transmission is crucial for developing effective influenza prevention and control strategies. METHODS:This modeling study analyzed data from 2017 to 2022, in Beijing, China. Weekly influenza positive rate and influenza-like rate were incorporated to quantify the community-level influenza activities. The effective reproduction number and influenza attack rate were estimated using a branching process model and a transmission dynamics model, respectively. The impact of PHSMs was quantified through log-linear regression and counterfactual simulations under varying PHSM scenarios. RESULTS:The transmissibility of influenza decreased by 68.41% (95%CI: 52.43, 78.80) in 2020, 67.07% (95%CI: 50.80, 77.89) in 2021 and 79.08% (95%CI: 63.18, 88.06) in 2022, and the attack rate dropped by 93.47% (95%CI: 85.86, 95.78), 95.37% (95%CI: 94.30, 96.89) and 71.61% (95%CI: 42.96, 81.24) over the same period, primarily due to the PHSMs. The simulation shows that strict PHSMs effectively suppressed the current flu epidemic effectively. When susceptible individuals drop to 50%, a relaxed strategy results in a smaller rebound in the next flu season, with epidemic sizes increasing to 1.18 (1.10, 1.30), 1.41 (1.20, 1.54), and 1.54 (1.35, 1.55) for relaxed, moderate, and strict measures, respectively. CONCLUSIONS:Our study confirms the suppressive effect of coronavirus disease 2019 PHSMs on influenza transmission in Beijing. However, the relaxation of these measures' triggers resurgence, emphasizing the need for adaptive control strategies tailored to the population susceptibility and epidemic dynamics.

This post-marketing surveillance study evaluated the safety of the adjuvanted recombinant zoster vaccine (RZV) in Chinese adults, given the limited country-specific safety data accumulated since the 2019 licensure of RZV in China for adults ≥ 50 years of age (YOA). This descriptive, prospective cohort study enrolled adults ≥ 50 YOA who voluntarily received RZV per routine clinical practice in six centers in China. The primary outcomes were occurrence, intensity, and causal relationship to vaccination of medically attended adverse events (MAEs) within 30 days post-any dose. The occurrence and causal relationship to RZV of serious AEs (SAEs) within 30 days post-any dose, and of SAEs and potential immune-mediated diseases (pIMDs) from dose 1 until 12 months post-last dose were secondary outcomes. The exposed set included 3,300 adults (mean age [standard deviation]: 61.2 [7.4] years; 67.1% female), of whom 3,175 completed the study. Fifty-six MAEs were recorded in 42 (1.3%, 95% confidence interval [CI]: 0.9-1.7%) participants; ≥1 grade 3 MAE was reported in six (0.2%, 0.1-0.4%) participants; 15 MAEs (in nine [0.3%, 0.1-0.5%] participants) were considered RZV-related. Within 30 days post-any dose, 12 SAEs were reported in 10 (0.3%, 0.1-0.6%) participants, while 29 SAEs in 22 (0.7%, 0.4-1.0%) participants were reported from post-dose 1 until 12 months post-last dose. The three reported fatal SAEs were not considered RZV-related. Three of the total seven pIMDs were considered RZV-related. The observed descriptive patterns of MAEs, SAEs, and pIMDs did not indicate safety concerns following RZV administration among Chinese adults ≥ 50 YOA.

The 20 μg (0–1–6 month) hepatitis B virus (HBV) vaccination is widely recommended for HBV vaccine-naïve immune adults in China. However, suboptimal protective responses may occur due to dose-series incompletion. We aim to investigate the immunogenicity of a 60 μg HB vaccine with a 0–2 month series among HBV vaccine-naïve immune adults aged 25–55 to assess potential alternative approaches for HB immunization. A two-center randomized controlled trial was carried out. Participants were randomly allocated to either the 20 μg (0–1–6 month) or the 60 μg (0–2 month) regimen. Blood samples were collected eight weeks after the final injection to measure the antibodies. A total of 583 adults (289 in the 20 μg regimen and 294 in the 60 μg regimen) were included. The seroprotection rates (SPRs) were 97.23% and 93.54% in the 20 μg and 60 μg regimens, respectively (p = 0.0261), and the geometric mean concentrations were 600.76 mIU/mL and 265.68 mIU/mL, respectively (p < 0.0001). The immunogenicity of the 60 μg regimen decreased significantly with age, particularly in adults aged 40 and older. The 60 μg regimen may be beneficial for adults under 40, especially those with poor compliance or in urgent need of immunization.

Objective: To investigate the distribution characteristics of body height, body weight and body mass index (BMI) in children aged 3-17 years in China. Methods: Data were obtained from the National Nutrition and Health Systematic Survey in 0-18 years old children in China. The study selected 70 853 children aged 3-17 years from 28 urban and rural survey sites in 14 provinces (autonomous regions and municipalities) in 7 regions of China with multi-stage stratified cluster random sampling. M (Q1, Q3) was used to describe the region, age and gender specific body height, body weight and BMI in the children aged 3-17 years. Wilcoxon rank sum test was used to compare the body height, body weight, and BMI between boys and girls in same age group. Kruskal-Wallis H rank sum test was used to compare the body height, body weight and BMI among boys in different age groups and among girls in different age groups, as well as among boys in same age group and among girls in same age group from different regions, and DSCF method was used for further pairwise comparisons. Results: In this study, the median body height and body weight were 172.0 cm and 62.9 kg in 17-year-old boys and 160.0 cm and 53.7 kg in 17-year-old girls. The median for children's body height, body weight, and BMI in most age groups were higher in northeastern and northern China than in southern China, and the differences could be observed until age 17 years. The differences in body weight and BMI in children in northeastern and northern China were greater in Q3 than in Q1 compared with southern China. Conclusions: The body height of children aged 3-17 years continues to increase in China. Northeastern and northern China have more children with higher bodyweight, showing an obvious body weight increase trend, to which close attention needs to be paid.

Objective: To analyze the relationship between body mass index (BMI) and fat mass percentage (FMP) in children aged 3-17 years in China. Methods: The BMI and FMP data of children aged 3-17 years from the National Nutrition and Health Systematic Survey in 0-18 years old children in China was analyzed. BMI-Z score/BMI and FMP were used to classify the subjects, respectively. Spearman correlation was used to analyze the correlation between BMI and FMP. The consistency between BMI-Z score/BMI and FMP in classifying the subjects was measured using Kappa coefficient. Results: The FMP of malnutrition, normal and overweight/obesity in boys was higher in age group 10-13-year than in other age groups (all P<0.001). The FMP of all nutritional status in girls increased with age (all P<0.05). The BMI of boys in all the FMP levels increased with age (all P<0.05). When the FMP of girls was 25%- or ≥30%, BMI increased with age (all P<0.001). The relationship between BMI and FMP was strong (r=0.705, P<0.001), with r of 0.618 in boys and 0.884 in girls. The consistency between BMI-Z score/BMI and FMP in classifying the subjects was found to be moderate (Kappa=0.574, P<0.001). Conclusions: There was a strong relationship between BMI and FMP. The consistency between BMI-Z score/BMI and FMP in classifying the subjects was moderate.

Objective: To evaluate the consistency between bioelectrical impedance analysis (BIA) and dual-energy X-ray absorptiometry (DXA) in the measurement of body composition in children aged 6-17 years in China. Methods: Fat-free mass, fat mass and fat mass percentage were measured by both BIA and DXA in 1 161 children. t-test or Wilcoxon paired test was used to evaluate the different outcome of the two methods. The correlation and consistency between the methods were evaluated by Spearman correlation coefficients (r) and Bland-Altman analysis. Results: Body compositions measured by BIA was positively correlated with those measured by DXA (fat mass r=0.95, fat-free mass r=0.98, fat mass percentage r=0.86, all P<0.05). Comparing with DXA, BIA underestimate children's fat mass [the mean difference is -3.15 kg, and the SD is 2.35 kg, 95% limits of agreement (LoA): -7.74-1.45 kg] and fat mass percentage (the mean difference is -8.45%, and the SD is 4.63%, 95% LoA: -17.53%-0.64%). Conclusions: Body compositions measured by BIA was highly positively correlated with those measured by DXA. BIA has certain application value in the measurement of body fat mass and fat-free mass of children aged 6-17 years.

Objective: To analyze the epidemiological characteristics and related factors of hepatitis C in Beijing City from 2004 to 2021. Methods: Descriptive epidemiological method and Joinpoint regression were used to analyze the trend and other epidemiological characteristics of hepatitis C in Beijing City from 2004 to 2021 in National Notifiable Disease Reporting System. According to a 1∶1 matched case-control study design, logistic regression was used to investigate the risk factors of hepatitis C infection in 2021. Results: From 2004 to 2021, the reported incidence of hepatitis C in Beijing City ranged from 2.37/100 000 to 10.46/100 000. The reported cases were mainly aged 30-60 years, and most of them were chronic. The reported incidence of hepatitis C showed an initial increase from 2004 to 2006 (APC=45.37%, 95%CI:-1.56%-114.69%), and declined after 2006 (APC=-9.21%, 95%CI:-10.70%-7.70%). Logistic analysis showed that history of surgery (OR=1.84, 95%CI: 1.08-3.14) and previous blood transfusion (OR=34.22, 95%CI: 8.05-145.41) were risk factors for hepatitis C infection. Conclusion: The reported incidence of hepatitis C in Beijing City increases first and decreases later. It currently remains at a low level. The risk factors of infection are surgery and blood transfusion history. Safe blood supply and preventing iatrogenic transmission should be focused on the prevention of hepatitis C transmission.

Objective: To understand the changes in pain and its effects in patients with the diagnosis of herpes zoster. Methods: A total of 3 487 patients diagnosed with herpes zoster (HZ) for the first time at the outpatient department of Miyun District Hospital from January 1, 2017, to December 31, 2019, were included in the study. The information of patients was registered and issued with a record card. Patients were required to record the time of pain and rash by themselves. Telephone follow-up was conducted at 21, 90, 180 and 365 days after the onset of rashes, including hospitalization, location of rash and pain, and the time of start and end. The impact of pain on life was evaluated by the Zoster Brief Pain Inventory (ZBPI). Results: The age of 2 999 HZ patients included in the analysis were (53±16) years old, including 1 377 (45.91%) males and 1 903 (63.45%) patients aged 50 years and older. After 21 days of rash, mild, moderate and severe pain accounted for 20.87% (626 cases), 37.98% (1 139 cases) and 33.81% (1 014 cases), respectively. Only 5.07% (152 cases) had no pain or discomfort, and 2.27% (68 cases) had no pain but discomfort. Most of the pain sites were consistent with the rash sites. The chest and back and waist and abdomen were the most common, accounting for 35.58% (1 067 cases) and 29.18% (875 cases), respectively, followed by the limbs and face and neck, accounting for 16.74% (502 cases) and 16.40% (492 cases), respectively. The M (Q1, Q3) of pain days in the HZ patients was 14 (8, 20) days, and the incidence of post-herpetic neuralgia (PHN) was 6.63% (171/2 580) (excluding 419 patients who refused to visit or lost to visit on 90 days after the onset of rash). The pain score of HZ patients within 21 days after the rash was (5.19±2.73) points, and the pain score of PHN patients was (7.61±2.13) points, which was significantly higher than that of non-PHN patients [(5.04±2.69) points] (P<0.001). Daily activities, emotions, walking ability, work, social interaction, sleep and recreation were affected for 21 days after the rash in HZ patients, ranging from 60.79% to 83.83%, with sleep being the most affected (83.83%). The impact scores of pain and life dimensions in PHN patients ranged from 4.59 to 7.61 points on the ZBPI scale, which were higher than those in non-PHN patients (2.49-5.04) (t values ranged from 8.86 to 11.67, all P values <0.001). Conclusion: The proportion of pain in HZ patients after the diagnosis is high, and the pain is more obvious in patients with PHN and HZ patients aged 50 and older, which has a greater impact on their daily lives.

Hepatitis B (HB) vaccination is recommended for people with human immunodeficiency virus/acquired immune deficiency syndrome (HIV/AIDS). We aimed to assess the immune response to the HB vaccine and associated factors using the standard vaccination schedule among people with HIV (PWH) in China. A prospective study was carried out from 2016 to 2020 in Beijing, China. PWH were given three 20 μg doses of recombinant HB vaccine at 0, 1, and 6 months. Blood samples were taken within 4–6 weeks after each dose to evaluate the anti-HBs levels. A total of 312 participants completed vaccination and serologic testing. The seroconversion (anti-HBs ≥ 10 IU/L) rates following the first, second, and third doses of the vaccine were 35.6% (95% CI: 30.3–40.9%), 55.1% (95% CI: 49.6–60.7%), and 86.5% (95% CI: 82.8–90.3%), respectively, and the geometric means of the anti-HBs titers were 0.8 IU/L (95% CI: 0.5–1.6 IU/L), 15.7 IU/L (95% CI: 9.4–26.3 IU/L), and 241.0 IU/L (95% CI: 170.3–341.1 IU/L), respectively. In multivariate analysis, after three doses of vaccination, age, CD4 cell count, and HIV-RNA viral load were significantly associated with strong, moderate, and weak response, respectively. These findings confirm that these personal health conditions are related to the HB response. HB vaccination in PWH using the standard schedule was still highly effective in the context of early treatment initiation, especially among participants aged 30 years and younger.

An epidemiological investigation was conducted on a cluster epidemic of COVID-19 in the vaccinated population in Beijing in 2022, and serum samples were collected from 21 infected cases and 61 close contacts (including 20 cases with positive nucleic acid in the isolation observation period). The results of antibody detection showed that the IgM antibody of two infected persons was positive, and the IgG antibody positive rates of patients who were converted, not converted to positive and infected persons were 36.84% (7/19), 63.41% (26/41) and 71.43% (15/21), respectively. About 98.78% of patients had been vaccinated with the SARS-CoV-2 inactivated vaccine. The positive rate of IgG antibody in patients immunized with three doses of vaccine was 86.00% (43/50), which was higher than that in patients with one or two doses [16.12% (5/31)]. The antibody level of M (Q1, Q3) in patients immunized with three doses was 4.255 (2.303, 7.0375), which was higher than that in patients with one or two doses [0.500 (0.500, 0.500)] (all P values<0.001). The antibody level of patients who were vaccinated less than three months [7.335 (1.909, 7.858)] was higher than that of patients vaccinated more than three months after the last vaccination [2.125 (0.500, 4.418)] (P=0.007). The positive rate and level of IgG antibody in patients who were converted to positive after three doses were 77.78% (7/9) and 4.207 (2.216, 7.099), respectively, which were higher than those in patients who were converted after one or two doses [0 and 0.500 (0.500, 0.500)] (all P values<0.05).

Objective: To investigate the infection sources and the transmission chains of three outbreaks caused by 2019-nCoV Omicron variant possibly spread through cross-border logistics in Beijing. Methods: Epidemiological investigation and big data were used to identify the exposure points of the cases. Close contacts were traced from the exposure points, and the cases' and environmental samples were collected for nucleic acid tests. Positive samples were analyzed by gene sequencing. Results: The Omicron variant causing 3 outbreaks in Beijing from January to April, 2022 belonged to BA.1, BA.1.1 and BA.2. The outbreaks lasted for 8, 12 and 8 days respectively, and 6, 42 and 32 cases infected with 2019-nCoV were reported respectively. International mail might be the infection source for 1 outbreak, and imported clothes might be the infection sources for another 2 outbreaks. The interval between the shipment start time of the imported goods and the infection time of the index case was 3-4 days. The mean incubation period (Q1, Q3) was 3 (2,4) days and the mean serial interval (Q1, Q3) was 3 (2,4)days. Conclusions: The 3 outbreaks highlighted the risk of infection by Omicron variant from international logistics-related imported goods at normal temperature. Omicron variant has stronger transmissibility, indicating that rapid epidemiological investigation and strict management are needed.

目的 探讨北京市朝阳区常住人群乙型肝炎(乙肝)病毒血清标志物流行情况随年龄、时期、出生队列等影响因素的变化趋势.方法 分别于2010年、2015 年、2020年按照多阶段整群随机抽样的方法,在北京市朝阳区1～75 岁常住人口中进行抽样,收集其人口学信息的同时采集静脉血3～5 mL,使用化学免疫发光法进行乙肝表面抗原(HBsAg)、乙肝表面抗体(HBsAb)、乙肝核心抗体(HBcAb)等检测,运用年龄-时期-队列模型和内生因子法分别估计HBsAg 阳性率、HBsAb 阳性率和乙肝感染率的年龄、时期、队列等效应.结果 三次调查显示朝阳区常住居民HBsAg 阳性率差异无统计学意义(标化率2.61％、2.50％、2.52％,P=0.830,x2=0.374).乙肝感染率的年龄-时期-队列效应差异有统计学意义,随年龄增加先增大后减小、40～岁年龄组最高,队列暴露风险随出生年代增加而减小.结论 北京市朝阳区HBsAg 阳性率处于乙肝中流行区水平;乙肝暴露风险随年龄增加先增大后减小,随出生队列的增加而减小.

Background:Herpes zoster (HZ) and post-herpetic neuralgia (PHN) cause considerable morbidity, especially in elderly adults, but the burden is under-recognized in mainland China. Methods:We conducted a case registry and follow-up study of HZ in Miyun District, Beijing from January 1, 2017 through December 31, 2018. Registered HZ cases were followed-up for pain to 365 days. The first 50 patients with HZ in each age group (≤14, 15-29, 30-39, 40-49, 50-59, 60- 69, 70-79, ≥80 years) and all those with PHN completed the EuroQoL five dimensions questionnaire (EQ-5D) to evaluate health-related quality of life (HRQoL) in patients with HZ and PHN. Ratings using the EQ-5D dimensions, visual analogue scale (VAS), health utility score (HUS) and quality-adjusted life years (QALYs) lost were compared among age groups. Results:In total, 2008 patients with HZ were followed for a median 22 days (interquartile range[IQR] = 20-90), with an estimated incidence of 4.39 per 1000 person-years. We identified 122 (6.08 %) PHN cases. The median age of patients with PHN (65 years, IQR = 55-71) was older than that of patients with HZ (54 years, IQR = 43-64) (P < 0.001). The median duration of pain was 170 days (IQR = 144-355.5) for PHN and 15 days (IQR = 9-25) for HZ. All 95 patients with PHN and 319 sampled patients with HZ completed the EQ-5D survey. The median QALY loss of HZ increased from 0.004 (IQR = 0.001-0.02) in patients 50-59 years old to 0.02 (IQR = 0.01-0.06) in those ≥ 80 years old (P < 0.01). After weighting for age, the mean QALY loss per HZ case was estimated at 0.02 (standard deviation [SD] 0.04). The mean QALY loss per PHN case was 0.13 years (SD 0.12). Conclusions:HZ and PHN caused a substantial burden, especially among adults aged ≥ 50 years in Miyun District, Beijing, China. Vaccination should be considered to alleviate the burden of this painful disease.

目的 获得北京市市区居民及医务人员对丙型肝炎(丙肝)知识的知晓及诊治和报告情况,为开展不同人群的丙肝知识宣教和提高丙肝诊断报告质量提供依据.方法 2021年在北京市开展现场调查,社区居民调查采用横断面调查方法,选取北京市东城和通州区作为调查点,每个区按照容量比例抽样原则(PPS)各选取4个社区,每社区随机抽取100名15～65岁居民进行调查.医务人员调查根据2018-2020年丙肝报告病例数和医院级别,选择报告病例数前7家医院的临床医生进行调查.结果 社区居民调查收集有效问卷893份,丙肝基本知识知晓率仅为37.40％;婚姻状况(x2=11.03,P＜0.05)和文化程度(x2=39.98,P＜0.05)是社区人群丙肝基本知识的知晓的影响因素.医务人员调查收集有效问卷498份,丙肝基本知识知晓率达95.98％,但专业知识知晓率为20.08％,对于"丙肝病例的诊断分类"和"丙肝临床诊断病例的诊断依据"的知晓率不足10.00％;文化程度(OR=3.35,95％CI:1.82～6.17)、医院科室(OR=0.40,95％CI:0.20～0.78)和近1年是否接受过丙肝专业培训(OR=10.33,95％CI:1.34～79.79)是医务人员丙肝专业知识知晓的影响因素.结论 社区居民对丙肝知识知晓率较低,尤其是对丙肝临床表现认知存在误区.医务人员丙肝基本知识知晓率较高,但专业知识知晓率较低,尤其是对丙肝临床诊断和分类掌握较差.今后应在不同人群开展差异化健康宣教,对医务人员加强丙肝专业知识培训.

Objective: To investigate the source and the transmission chain of a cold-chain product associated COVID-19 epidemic caused by 2019-nCoV Delta variant in Beijing. Methods: Epidemiological investigation were used to verify the exposure points of the cases. Close contacts were traced from the exposure points, and human and environmental samples were collected for nucleic acid tests. Positive samples were analyzed by gene sequencing. Results: A total of 112 cases of COVID-19 were reported in the epidemic from January 18 to February 6, 2022 in Beijing. Except for 1 case was uncertain, there were epidemiological links among 111 cases. The source of infection was the packages of imported cold-chain products from Southeast Asia, which were harvested and stored in a local cold-storage in January 2021, and packaged and sent to the cold-storage A in A district in June 2021, and then sold in batches in cold-storage B in B district from January 2022. The first case was infected in the handling of positive frozen products, and then 77 cases occurred due to working, eating and living together with the index case in the cold-storage B, cold-storage C and restaurant D. Besides the cold-storage B, C and the restaurant D, there were 16 sub-transmission chains, resulting in additional 35 cases. Conclusion: The epidemic indicated that the risk of 2019-nCoV infection from imported cold-chain products contaminated by package and highlighted the importance to strengthen the management of cold-chain industry in future.

The Beijing 2022 Olympic and Paralympic Winter Games in Beijing (Beijing 2022 Games) were taking place at the height of the fourth wave of the global COVID-19 pandemic caused by the Omicron variant. Through a set of adjustments of COVID-19 prevention and control policies and practices, such as vaccine coverage, whole-journey closed-loop management, daily nucleic acid testing, wearing N95 masks, as well as social distancing, Beijing 2022 Games obtained exceptional achievement of public health security that the Games were held as scheduled and the health safety of all participants was under protection. It further provides valuable reference to the countermeasures at societal level.

Objective: To assess the level and trend of varicella-zoster virus (VZV) antibody among healthy population in Beijing in 2017, after the five-year implementation of the two doses varicella vaccination strategy in 2012, and to provide evidence for scientific evaluation of immunization strategy. Methods: A total of 2 144 subjects in ten age groups from 8 districts of Beijing city were recruited in this study using cross-sectional survey based on multi-stage cluster random sampling method. Serum samples were collected and VZV antibody was detected by ELISA. The influencing factors of antibody concentration and positive rate were analyzed and compared with the study in 2012. The antibody concentration and antibody positive rate were analyzed by nonparametric test and χ² test respectively. Results: The ratio of subjects with registered residence in Beijing city to other provinces was 1∶1. The ratio of male to female was 1∶1.08. The median concentration of VZV antibody was 341.4 (78.6, 1 497.8) mIU/ml, and the total antibody positive rate was 71.1% (1 524/2 144). There were significant differences in antibody positive rate (χ²=736.39, P<0.01) and antibody concentration (χ²=740.34, P<0.01) among different age groups. The antibody positive rate generally increased with age (χ²trend=7.32, Ptrend<0.01). Among 862 children under 14 years old, the antibody positive rate of two doses vaccination 72.8% (182/250) was significantly higher than that of one dose vaccination 51.9% (154/297) (χ²=25.14, P<0.01). There was significant difference between 1-4 years old group (χ²=11.71, P<0.01) and 10-14 years old group (χ²=5.95, P=0.02), but not in 5-9 years old group (χ²=3.00, P=0.07). Compared with the study in 2012, the antibody positive rate increased in 5-9 years old group (χ²=14.35, P<0.01) and decreased in 1-4 years old group (χ²=11.51, P=0.01) in 2017. Conclusion: The recommended varicella booster vaccination has significantly improved the VZV antibody level of children in Beijing city. In the future, it is necessary to explore a more optimized two doses varicella vaccination schedule for children in combination with epidemiological evidence.

Objective:To compare and analyze preliminarily the countermeasure strategies against coronavirus disease 2019 (COVID-19) in the Tokyo 2020 Olympic Summer Games (Tokyo 2020 Games) and Beijing 2022 Olympic Winter Games (Beijing 2022 Games), and to summarize the experience obtained from the two Games.Methods:Public available data were collected from the official websites of Beijing 2022 Games, Tokyo 2020 Games, International Olympic Committee and World Health Organization, as well as publications in academic journals. The countermeasure strategies applied by the host countries and at Games time as well as the effectiveness were compared.Results:The 'Closed-loop Management’ or 'Bubble Regime’ was employed in the two Games. The Closed-loop Management of Beijing 2022 Games covered the whole journey of the participants who were completely apart from the local residents. In Tokyo 2020 Games, COVID-19 antigen tests of saliva were adopted for screening followed by PCR tests of nasopharyngeal swab samples as the confirmation. The test frequencies were in line with the four types of participants. In Beijing 2022 Games, daily PCR tests for oropharyngeal swab samples were conducted for screening to all individuals in the closed loop followed by PCR tests for nasopharyngeal swab samples as the confirmation. In addition, participants of Beijing 2022 Games were required to wear N95 respirator or face masks of equivalent protection. Furthermore, only the participants with full vaccination or completion of 21-day isolation were allowed to enter the closed loop in Beijing 2022 Games.Conclusions:The countermeasure strategies of Beijing 2022 Games and Tokyo 2020 Games were developed on their specific situations and achieved noticeable effects. These provided references for preparedness of future mass-gathering events within the period of infectious disease pandemic.

目的 拟合北京市某冷库新型冠状病毒肺炎疫情走势,了解疫情流行特征参数,评价综合防控措施效果.方法 基于本轮疫情每日累计发病人数建立SEIAR传染病动力学模型,使用马尔可夫蒙特卡洛算法估计实时再生数(time-varying reproduction number,Rt),模拟防控措施提升实施时间对疫情走势的影响.结果 本轮疫情历时20 d,感染112人,初期R,值为3.33(95％CI:2.14～4.89),首例疫情报告后第5日防控措施进一步提升,Rt值在之后的5 d内下降到0.97,10 d内降到0.31.若提升防控措施日期延迟7 d,则累计发病人数将达到339例,最终清零时间将延迟14 d.结论 北京市针对本次疫情所采取的综合防控措施阻止了疫情规模的进一步扩大,疫情防控升级的时间节点在可疑扩散的情况下,越早越好.

Objective To investigate neutralizing antibody levels in symptomatic and asymptomatic patients with coronavirus disease 2019（COVID-19） at 6 and 10 months after disease onset.Methods Blood samples were collected at three different time points from 27 asymptomatic individuals and 69 symptomatic patients infected with severe acute respiratory syndrome coronavirus 2（SARS-Co V-2）. Virus-neutralizing antibody titers against SARS-CoV-2 in both groups were measured and statistically analyzed.Results The symptomatic and asymptomatic groups had higher neutralizing antibodies at 3 months and 1–2 months post polymerase chain reaction confirmation, respectively. However, neutralizing antibodies in both groups dropped significantly to lower levels at 6 months post-PCR confirmation.Conclusion Continued monitoring of symptomatic and asymptomatic individuals with COVID-19 is key to controlling the infection.