[Theoretical models for influenza vaccination behavior at the individual level].

Influenza imposes a significant disease burden on society and individuals annually, and influenza vaccination is considered a significant public health measure to prevent influenza and reduce influenza-related severe disease and death. The low influenza vaccination rate in China is partly due to certain factors affecting the willingness and behavior of individuals to receive them. Scientific research and targeted interventions on these factors can effectively improve the vaccination situation. Commonly used individual-level theoretical models for influenza vaccination behavior include the health belief model, protection motivation theory, and theory of planned behavior. This study reviews theoretical models commonly employed in researching influenza vaccination willingness and behavior. An overview of these practical applications and challenges models is presented to provide references for relevant research and intervention programs in China.

[Summary of key viral respiratory infectious diseases surveillance in some countries and regions in the world].

Respiratory virus infections spread quickly, and some diseases are even more likely to cause a global epidemic. In order to explore how better to carry out surveillance of viral respiratory infectious diseases, the author searched the surveillance situation of key viral respiratory infectious diseases in America, Europe, and China, et al., then put forward several suggestions such as strengthening application of information technology, broaden monitoring channels, building early monitoring and early warning mechanisms.

[Progress in research of influenza vaccination in pregnant women].

Influenza is an acute respiratory infectious disease caused by influenza virus. Pregnancy is associated with physiologic and immunological changes that may increase the risk for influenza virus infection and influenza-related complications. Influenza vaccination is the most effective way to prevent influenza virus infection. WHO and many countries have classified pregnant women as a priority population for influenza vaccination, however, there are still many challenges for promoting influenza vaccination in pregnant women in China, influenza vaccination coverage in pregnant women remains low and some influenza vaccine package inserts list pregnancy as an absolute contraindication. In this paper, we summarize the research progress in the effects of influenza infection and influenza vaccination during pregnancy both at home and abroad, then discuss the strategies to promote influenza vaccination in pregnancy for the purpose of providing reference for the related research and policy development in China.

[Performance of screening of contacts of COVID-19 cases in same flight].

Objective: To understand the performance of 2019-nCoV nucleic acid detection in screening of contacts of COVID-19 cases in same flights and provide evidence for the effective screening of persons at high risk for the infection in domestic flights. Methods: The information of passengers who took same domestic flights with COVID-19 cases in China from April 1, 2020 to April 30, 2022 were retrospectively collected,and χ2 test was used to analyze positive nucleic acid detection rates in the passengers in different times before the onsets of the index cases, in different seat rows and in epidemic periods of different 2019-nCoV variants. Results: During the study period, a total of 433 index cases were identified among 23 548 passengers in 370 flights. Subsequently, 72 positive cases of 2019-nCoV nucleic acid were detected in the passengers, in whom 57 were accompanying persons of the index cases. Further analysis of the another 15 passengers who tested positive for the nucleic acid showed that 86.67% of them had onsets or positive detections within 3 days after the diagnosis of the index cases, and the boarding times were all within 4 days before the onsets of the index cases. The positive detection rate in the passengers who seated in first three rows before and after the index cases was 0.15% (95%CI: 0.08%-0.27%), significantly higher than in the passengers in other rows (0.04%, 95%CI: 0.02%-0.10%, P=0.007),and there was no significant difference in the positive detection rate among the passengers in each of the 3 rows before and after the index cases (P=0.577). No significant differences were found in the positive detection rate in the passengers, except the accompanying persons, among the epidemics caused by different 2019-nCoV variants (P=0.565). During the Omicron epidemic period, all the positive detections in the passengers, except the accompanying persons, were within 3 days before the onset of the index cases. Conclusions: The screening test of 2019-nCoV nucleic acid can be conducted in the passengers took the same flights within 4 days before the onsets of the index cases on board. Passengers who seated within 3 rows from the index cases can considered as the close contacts at high risk for 2019-nCoV, for whom screening should be conducted first and special managements are needed. The passengers in other rows can be classified as general risk persons for screening and management.

[Investigation on influenza vaccination policy and vaccination situation during the influenza seasons of 2020-2021 and 2021-2022 in China].

Objective: To investigate the policies and coverage of influenza vaccine during the influenza epidemic seasons of 2020-2021 and 2021-2022 in China. Methods: The national influenza vaccination policy and vaccination rate were investigated in counties and districts and described in the two epidemic seasons. Results: In the epidemic seasons of 2020-2021 and 2021-2022, the vaccination coverage of influenza in China was 3.16% and 2.47%, respectively. The free vaccination policy had the highest vaccination coverage (51.75% and 38.32%), followed by the medical insurance reimbursement policy (9.74% and 7.36%). During the epidemic season of 2021-2022, the number of counties and districts implementing the free vaccination policy in China decreased 61 compared with the previous year, but the number of people covered increased by 51.29%. However, the vaccination coverage of the vast population decreased significantly, with the medical staff (75.69% and 40.15% for two epidemic seasons), preschool children (58.86% and 26.15%), and the elderly (45.71% and 32.94%). During the epidemic season of 2021-2022, the number of counties and districts implementing the medical insurance reimbursement policy increased by 6 compared with the previous year, and the number of people covered increased by 11.12%, but the vaccination coverage decreased. Conclusion: The influenza vaccination rate in China is low, and the implementation of cost preferential policy can greatly improve the influenza vaccination rate.

[Analysis of influenza vaccination coverage, recommendation behaviors and related factors among health care workers in Nanshan district of Shenzhen city under the free policy between 2019 and 2020].

Objective: To investigate the current situation of influenza vaccination, vaccination willingness, recommended behavior and influencing factors of health care workers (HCWs) under the policy of free vaccination. Methods: A cross-sectional survey was conducted among 3 167 medical staff from 8 hospitals in Nanshan district of Shenzhen city based on a web-based questionnaire platform. The logistic regression was used to analyze the data. Results: The influenza vaccination rate in HCWs was 23.97%, and the recommendation rate was 25.69% from 2019 to 2020. Staff with high professional titles, high academic qualifications, and positive awareness about influenza vaccine had a higher vaccination rate. The main reasons for not recommending influenza vaccine were the fear of patients' misunderstanding of commercial benefits, fear of possible disputes caused by recommended vaccination, lack of national or institutional requirements for recommended influenza vaccine, and fear of adverse reactions of influenza vaccines. Conclusion: Under the free policy, the influenza vaccination rate and recommendation rate of HCWs in Nanshan district of Shenzhen city are relatively low. Strengthening health education on influenza and related knowledge, publicizing the policy of free influenza vaccination, providing convenient vaccination services and promoting the construction of relevant policies and regulations are the key to improve the influenza vaccination rate and recommendation rate among HCWs.

[Thoughts and suggestions on co-administration of seasonal influenza vaccine and COVID-19 vaccine].

In the context of the global pandemic of COVID-19, the epidemic intensity, epidemic characteristics and infection risk of influenza have presented new features. COVID-19 and influenza have simultaneously emerged in many regions of the world. COVID-19 and influenza are similar in terms of transmission mode, clinical symptoms and other aspects. There are also similarities in the mechanism of influenza virus and novel coronavirus on cells. At the same time, it is feasible and significant to do a good job in the prevention and control of COVID-19 and influenza. This paper discusses the relevant strategies and measures for the joint prevention and control of influenza and novel coronavirus from the aspects of influenza vaccination to prevent co-infection, simultaneous vaccination of influenza vaccine and novel coronavirus vaccine, etc., and puts forward corresponding thoughts and suggestions, in order to provide scientific support for the formulation of strategies on seasonal influenza vaccine and novel coronavirus vaccination.

[Time distribution of positive nucleic acid detection in imported cases infected with SARS-CoV-2 in China].

Objective: To analyze the time distribution of the first positive nucleic acid detection in imported cases infected with SARS-CoV-2 reported nationwide in China and provide references for further improvement of the prevention and control of COVID-19 in international travelers. Methods: The data of imported cases infected with SARS-CoV-2 reported by provinces from 24 July 2020 and 23 July 2021 were collected for the analysis on the time distribution of the first positive nucleic acid detection after entering China. Results: A total of 7 199 imported cases infected with SARS-CoV-2 were reported in 28 provinces during 24 July 2020 to 23 July 2021. The median interval (Q1, Q3) from the entry to the first positive nucleic acid detection of SARS-CoV-2 was 1 (0, 5) day. The imported cases who had the first positive nucleic acid detections within 14 days and 14 days later after the entry accounted for 95.15% (6 850/7 199) and 4.85% (349/7 199) respectively. Among these cases, 3.65% (263/7 199), 0.88% (63/7 199) and 0.32% (23/7 199) had the first positive nucleic acid detections within 15-21 days, 22-28 days and 28 days later after the entry respectively. The proportion of asymptomatic infections were 47.24% (3 236/6 850) and 63.61% (222/349) among the cases who had the first positive nucleic acid detections within 14 days and 14 days later after the entry respectively. A total of 39.54% (138/349) of cases infected with SARS-CoV-2 with the first positive nucleic acid detections 14 days later after the entry had inter-provincial travel after the discharge of entry point isolation. Conclusions: About 5% of the imported cases infected with SARS-CoV-2 were first positive 14 days later after the entry. In order to effectively reduce the risk of domestic COVID-19 secondary outbreaks caused by imported cases, it is suggested to add a nucleic acid test on 8th -13th day after the entry.

[Consideration on implementation of co-administration of Seasonal Influenza and COVID-19 vaccines during pandemic in China].

Influenza is an infectious respiratory disease caused by the influenza viruses. Older people, infants and people with underlying medical conditions could have a higher risk of severe influenza symptoms and complications. The co-infection of Coronavirus Diseases 2019 (COVID-19) with influenza viruses could lead to the complication of prevention, diagnosis, control, treatment, and recovery of COVID-19. Influenza vaccine and COVID-19 vaccine overlapped in target populations, vaccination time, and inoculation units. Although there was insufficient evidence on the immunogenicity and safety of co-administration of influenza vaccine and COVID-19 vaccine, World Health Organization and some countries recommended co-administration of inactivated influenza vaccine and COVID-19 vaccine. This review summarized domestic and international vaccination policies and research progress, and put forward corresponding suggestions in order to provide scientific support for the formulation of vaccination strategy on seasonal influenza vaccine and COVID-19 vaccine.

[Investigation of incidence of acute respiratory infection and healthcare-seeking behavior in period of COVID-19 epidemic].

Objective: To analyze the incidence of acute respiratory infection (ARI) and related healthcare seeking behaviors in population in the period of COVID-19 epidemic in China. Methods: According to the province specific cumulative incidence rates of COVID-19 reported as of March 31, 2020, the low, medium and high-risk areas were classified. In these areas, a stratified two stage cluster random sampling method was used to select participants for face-to-face questionnaire surveys. Data on the incidence of ARI and related healthcare seeking behaviors in community residents during COVID-19 epidemic period were collected to calculate the attack rate of ARI and related healthcare seeking rate. Logistic regression method was used to explore the influencing factors for ARI incidence and healthcare seeking behavior. Results: A total of 34 857 community residents were surveyed, in whom 647 (1.9%) reported that they had ARI symptoms during the COVID-19 epidemic period, and 241 (37.2%) had healthcare seeking behaviors. In terms of the incidence of COVID-19-related ARI, in high-risk area, the risk of COVID-19-related ARI was 1.36 times (95%CI: 1.12-1.65) than that in low-risk area; among different age groups, the risk of COVID-19-related ARI in age groups 20-39 years, ≥60 years was 1.80 times (95%CI: 1.29-2.59) and 1.63 times (95%CI: 1.14-2.40) than that in age group 1-9 years; the risk of COVID-19-related ARI in people with underlying diseases was 1.53 times (95%CI: 1.23-1.89) than that in those without underlying diseases; the risk of COVID-19-related ARI in people with contacts with confirmed cases of COVID-19 and people with fever or respiratory symptoms was 1.53 times (95%CI: 1.01-2.27) and 6.60 times (95%CI: 5.05-8.53) than those in people without these contacts. The healthcare seeking rate in COVID-19-related ARI patients with exposures to those with fever or respiratory symptoms was 1.68 times (95%CI: 1.05-2.70) than that in such patients without the exposures. Conclusions: The attack rate of COVID-19-related ARI was affected by the local epidemic level of COVID-19, and in high-risk area, the attack rate of COVID-19-related ARI was also high. The healthcare seeking rate in patients with COVID-19-related ARI was low. Therefore, it is necessary to encourage the healthcare seeking in people with ARI in COVID-19 pandemic period.

[Effectiveness of the "14 plus 7 day quarantine" and "nucleic acid plus total antibody testing" strategy for screening imported patients with COVID-19 in Xiamen].

Objective: To analysis effectiveness of the "14 plus 7 day quarantine" and "nucleic acid plus total antibody testing" strategy (combined screening strategy) for screenin the imported patients with COVID-19 in Xiamen. Methods: The study populations were overseas travelers arriving in Xiamen from March 17 to December 31, 2020, and overseas travelers who had quarantine outside Xiamen for less than 21 days from July 18 to December 31, 2020. Data were collected and analyzed on the timing of detection, pathways, and test results of the imported patients with COVID-19 after implementing combined screening strategy. Results: A total of 304 imported patients with COVID-19 were found from 174 628 overseas travelers and 943 overseas travelers from other cities. A total of 163 cases (53.6%) were diagnosed by multitime, multisite intensive nucleic acid testing after positive finding in total antibody testing. Among them, 27 (8.9%) were first positive for nucleic acid in 14 plus 7 day quarantine and 136 were first positive for nucleic acid in 14-day quarantine. Only 8 of these individuals were tested positive for nucleic acid after positive total antibody testing. The other 128 individuals were tested positive for nucleic acid after being negative for average 2.3 times (maximum of 6 times). Aditional 155 cases might be detected by using the combined "14 plus 7 day quarantine" and " nucleic acid plus total antibody testing" strategy compared with "14-day quarantine and nucleic acid testing" strategy, accounting for 51.0% of the total inbound infections. So the combined screening strategy doubled the detection rate for imported patients with COVID-19. No second-generation case caused by overseas travelers had been reported in Xiamen as of February 26, 2021. Conclusions: Xiamen's combined screening strategy can effectively screen the imported patients with COVID-19 who were first positive for nucleic acid after 14 day quarantine. Compared with "14 day quarantine and nucleic acid testing", the combined screening strategy improved detection rate and further reduced the risk of the secondary transmission caused by the imported patients with COVID-19.

[Distribution and infectious characteristics of re-positive cases infected with SARS-CoV-2].

Domestic and foreign literatures related to the persistence of SARS-CoV-2 and the re-positive cases infected with SARS-CoV-2 were reviewed, and the characteristics and infectivity of the re-positive cases were analyzed to provide scientific evidence for the improvement of case management and the development of measures to stop the spread of SARS-CoV-2. Existing studies have shown that re-positive rate of SARS-CoV-2 ranged from 2.4% to 19.8%, the median of interval between re-positive detection and discharge was 4-15 days. Following the second course of the disease, the anti-SARS-CoV-2 IgM, IgG and IgA positive rates of the cases were 11.11%-86.08%, 52.00%-100.00% and 61.54%-100.00% respectively, the total antibody and neutralizing antibody positive rates were 98.72% and 88.46%. The viral load of the re-positive cases was lower than that in the initial infection. At least 3 380 re-positive cases have been reported globally. SARS-CoV-2 strains were isolated from the samples of 3 re-positive cases (1 immunodeficiency case and 2 cases with abnormal pulmonary imaging). There were close contacts that were infected by an asymptomatic case taking immunosuppressive agents. In conclusion, the infectivity of re-positive cases infected with SARS-CoV-2 is generally very low. Rare re-positive cases infected with SARS-CoV-2 might cause further transmission. The management approach for the re-positive cases can be based on the assessment of the individual transmission risk according to the pathogen detection results.

[Financing strategies and cost estimates of influenza vaccination for the elderly in China: explore a multi-party co-payment mechanism].

The disease burden and economic burden of seasonal influenza is substantial in China, and the Coronavirus disease 2019 (COVID-19) pandemic has brought new challenges to the prevention and control of influenza. As a priority group of influenza vaccination, the elderly are at higher risk of influenza-associated severe symptoms and deaths, and they are more price-sensitive vaccine users with better cost-effectiveness of vaccination program. Therefore, a reasonable financing mechanism of influenza vaccination should be designed for the elderly to increase their vaccination rate. This study proposes three financing strategies of influenza vaccination for the elderly in China, trying to explore the distribution of vaccination costs among individuals, central government and local governments under different financing strategies, including the individual-central-local mechanism (strategy 1), the central-local mechanism (strategy 2), and the local payment mechanism (strategy 3). Strategy 1 is feasible and sustainable for most regions in the short term. Strategy 2 is conducive to further increasing the vaccine coverage rate of the elderly. Strategy 3 encourages local fiscal payments to help relieve the financial pressure of the central government. The results revealed a relatively heavy financial burden of influenza vaccination for the elderly, and it is recommended to promote the development of a multiparty co-payment mechanism gradually based on local conditions.

[Advance on the infectivity of SARS-CoV-2 infection at different stages].

The studies on infectiousness of person infected with SARS-CoV-2 at different stages of illness are an important basis for making effective prevention and control measures such as investigating the infectious source, determining the scope of close contacts and the timing of case isolation. This review discusses the infectiousness of cases infected with SARS-CoV-2 in the incubation period, symptomatic period and convalescent period by reviewing national and international literatures, technical and professional guidelines. Existing researches suggest that the infectious viruses could be isolated at the end of the incubation period as well as since illness onset, and viral load in upper respiratory tract swabs reached the peak on day 4-6 after illness onset and thereafter began to decline, implying the infectiousness was relatively strong at the end of incubation period and within one week after illness onset. Although there were a few cases who tested positive for SARS-CoV-2 after recovery, no evidence was found to indicate these cases can cause the transmission.

[Analysis on prevention and control of some infectious diseases in the elderly aged 60 years and above in China and countermeasure recommendation].

As the progress of population aging in China, the proportion of elderly population is increasing. Both chronic diseases and infectious diseases can threaten the health of the elderly. There are many kinds of infectious diseases, including vaccine preventable infectious diseases affecting the health of adults, such as influenza, pneumococcal diseases and herpes zoster. In addition, the newly emerged COVID-19 has caused a pandemic in the world, resulting the highest proportion of deaths occurred in the elderly and posing a serious threat to the health of the elderly. This paper mainly summarizes the prevention and control of vaccine preventable diseases and COVID-19 to which the elderly are susceptible, analyzes the infectious disease problems affecting the health of elderly population, and recommends countermeasures for the prevention and control of these diseases in elderly population.

[Progress in research of specific antibody dynamic characteristics in patients with COVID-19].

COVID-19 is an emerging infectious disease caused by SARS-CoV-2. After the infection of the virus, the host immune system is stimulated to produce multifarious specific antibodies to decrease or eliminate effects of the pathogen. Study of the specific antibodies dynamic characteristics in patients with COVID-19 is very important for the understanding and diagnosis of the disease, research and development of vaccine, and planning of prevention and control strategy. This paper reviews and summarizes the domestic and oversea research on dynamic characteristics of specific antibodies of COVID-19 patients, including the antibody producing, duration and level, and its possible influencing factors in order to improve the understanding of the immunological characteristics of COVID-19.

[Analysis on seasonality, age distribution of influenza B cases and matching degree of influenza B vaccine in China, 2011-2019].

Objective: To analyze the seasonality, age distribution of influenza B cases and matching degree of influenza B vaccine in China from 2011 to 2019, and provide evidences for the future surveillance, estimation of disease burden of influenza B, application of quadrivalent vaccines, and development of vaccine strategies. Methods: The epidemiological and virological surveillance data of influenza B from week 14 of 2011 to week 13 of 2019 obtained from National Influenza Surveillance Network were used to draw hot spot maps and conduct descriptive statistics to analyze the seasonality and age distribution of influenza B cases. The published antigenicity analysis results from the China Weekly Influenza Report were used to analyze the matching degree between the trivalent vaccine strain and the circulating influenza B strains. Results: From 2011 to 2019, the incidence of influenza B showed obvious seasonal characteristics, and influenza B virus co-circulated with influenza A virus in six winter-spring seasons, and influenza B virus/Victoria and Yamagata lineages circulated alternately. In some southern provinces, two lineages co-circulated in some southern areas in certain years. The age distribution of influenza B cases was double-peaked, and both lineages had the highest positive rate in age-group 5-15 years, with peaks at age of 10 years; B/Victoria virus had a sub-peak in age-group 25-35 years; B/Yamagata virus had a sub-peak in age-group 55-65 years. Trivalent influenza vaccine strain and influenza B epidemic strains mismatched in 2015-2016 and 2017-2018 seasons, matched in 2011-2012, 2012-2013, 2013-2014, 2014-2015 and 2016-2017 seasons, and moderately matched in 2018-2019 season, but reactivity was low. Conclusions: Influenza B mainly occurred in winter-spring season in China, and its intensity was lower than that of influenza A. There was a difference in the age distribution of the cases among different virus strains. Trivalent influenza vaccine strains and influenza B epidemic strains mismatched in several seasons. It is crucial to conduct continuous surveillance of influenza B and disease burden evaluation, improve vaccine immunization strategy, increase influenza vaccination rate to reduce the harm of influenza B in high-risk groups.

[Early containment strategies and core measures for prevention and control of novel coronavirus pneumonia in China].

In December 2019, novel coronavirus pneumonia epidemic occurred in Wuhan, Hubei Province, and spread rapidly across the country. In the early stages of the epidemic, China adopted the containment strategy and implemented a series of core measures around this strategic point, including social mobilization, strengthening case isolation and close contacts tracking management, blocking epidemic areas and traffic control to reduce personnel movements and increase social distance, environmental measures and personal protection, with a view to controlling the epidemic as soon as possible in limited areas such as Wuhan. This article summarizes the background, key points and core measures in the country and provinces. It sent prospects for future prevention and control strategies.

[Current situation and related policies on the implementation and promotion of influenza vaccination among health care workers].

Health care workers have higher risk of influenza infection because of their occupational exposure to infected patients. Infection of the health care workers may not only result in the increasing risk of the nosocomial infection and family transmission, but also disrupt the health services due to absence from work. Health care workers were recommended as a priority group of influenza vaccinationin more than 40 countries and regions in the world. In recent years, domestic surveys show that the influenza vaccine coverage among health care workers was low. This paper outlines the current status and related policies of influenza vaccination among health care workers in China and global. Additionally, we analyzed and discussed the proper immunization strategy of influenza vaccine for medical staff in China.

[Evaluation of the application of moving epidemic method on making influenza epidemic thresholds in the 7 climate zones in China].

Objective: We planned to evaluate the effectiveness of moving epidemic method (MEM) in calculating influenza epidemic threshold of 7 climatic zones in China mainland. Methods: The positive rate of influenza virus was obtained from the National Influenza Surveillance Network System from 2010/2011 to 2017/2018. We divided the 31 provinces into 7 climatic zones according to previous literatures and applied MEM to calculate the influenza epidemic threshold of 2018/2019 influenza season for these climatic zones. Sensitivity, specificity, positive predictive value and negative predictive value were calculated to evaluate the effectiveness of MEM. Results: Pre-epidemic threshold (the positive rate of influenza virus) varied from 9.66% (temperate zone) to 16.36% (subtropical zone) for 2018/2019 influenza season. The gap between pre-epidemic and post-epidemic thresholds was less than 5% except for plateau zone. The sensitivity was 86.16% (95CI:66.81%-98.23%), the specificity was 94.92% (95CI: 91.13%-98.41%), the positive predictive value was 89.87% (95%CI: 84.39%-94.38%), the negative predictive value was 92.96% (95%CI: 84.46%-99.17%). Conclusion: Overall, moving epidemic Method performs well in calculating influenza epidemic threshold in China, much better than the previous study.