Influenza is an acute respiratory infectious disease that is caused by the influenza virus, which seriously affects human health. The influenza virus has frequent antigenic drifts that can facilitate escape from pre-existing population immunity and lead to the rapid spread and annual seasonal epidemics. Influenza outbreaks occur in crowded settings, such as schools, kindergartens, and nursing homes. Seasonal influenza epidemics can cause 3-5 million severe cases and 290 000-650 000 respiratory disease-related deaths worldwide every year. Pregnant women, infants, adults 60 years and older, and individuals with comorbidities or underlying medical conditions are at the highest risk of severe illness and death from influenza. Given the ongoing COVID-19 pandemic, some provinces in southern China had a summer peak of influenza. 2019-nCoV may co-circulate with influenza and other respiratory viruses in the upcoming winter-spring influenza season. Annual influenza vaccination is an effective way to prevent influenza, reduce influenza-related severe illness and death, and reduce the harm caused by influenza-related diseases and the use of medical resources. The currently approved influenza vaccines in China include trivalent inactivated influenza vaccine (IIV3), quadrivalent inactivated influenza vaccine (IIV4), and trivalent live attenuated influenza vaccine (LAIV3). IIV3 is produced as a split virus vaccine and subunit vaccine; IIV4 is produced as a split virus vaccine; and LAIV3 is a live, attenuated virus vaccine. Except for some jurisdictions in China, the influenza vaccine is a non-immunization program vaccine-voluntarily and self-paid. China CDC has issued "Technical Guidelines for Seasonal Influenza Vaccination in China" every year from 2018 to 2021. Over the past year, new research evidence has been published at home and abroad. To better guide the prevention and control of influenza and vaccination in China, the National Immunization Advisory Committee (NIAC) Influenza Vaccination Technical Working Group updated and revised the 2021-2022 Technical Guidelines with the latest research progress into the "Technical Guidelines for Seasonal Influenza Vaccination in China (2022-2023)." The new version has updated five key areas: (1) new research evidence－especially research conducted in China－has been added, including new estimates of the burden of influenza disease, assessments of influenza vaccine effectiveness and safety, and analyses of the cost-effectiveness of influenza vaccination; (2) policies and measures for influenza prevention and control that were issued by the government over the past year; (3) influenza vaccines approved for marketing in China this year; (4) composition of trivalent and quadrivalent influenza vaccines for the 2022-2023 northern hemisphere influenza season; and (5) recommendations for influenza vaccination during the 2022-2023 influenza season. The 2022-2023 Guidelines recommend that vaccination clinics provide influenza vaccination services to all people aged 6 months and above who are willing to be vaccinated and have no contraindications to the influenza vaccine. For adults ≥18 years, co-administration of COVID-19 and inactivated influenza vaccines in separate arms is acceptable regarding immunogenicity and reactogenicity. For people under 18 years old, there should be at least 14 days between influenza vaccination and COVID-19 vaccination. The Guidelines express no preference for influenza vaccine type or manufacturer－any approved, age-appropriate influenza vaccines can be used. To minimize harm from influenza and limit the impact on the effort to prevent and control COVID-19 in China, the Technical Guidelines recommend priority vaccination of the following high-risk groups during the upcoming 2022-2023 influenza season: (1) healthcare workers, including clinical doctors and nurses, public health professionals, and quarantine professionals; (2) volunteers and staff who provide services and support for large events; (3) people living in nursing homes or welfare homes and staff who take care of vulnerable, at-risk individuals; (4) people who work in high population density settings, including teachers and students in kindergartens and primary and secondary schools, and prisoners and prison staff; and (5) people at high risk of influenza, including adults ≥60 years of age, children 6-59 months of age, individuals with comorbidities or underlying medical conditions, family members and caregivers of infants under 6 months of age, and pregnant women. Children 6 months to 8 years of age who receive inactivated influenza vaccine for the first time should receive two doses, with an inter-dose interval of 4 or more weeks. Children who previously received the influenza vaccine and anyone 9 years or older need only one dose. LAIV is recommended only for a single dose regardless of the previous influenza vaccination. Vaccination should begin as soon as influenza vaccines become available, and preferably should be completed before the onset of the local influenza season. Repeated influenza vaccination during a single influenza season is not recommended. Vaccination clinics should provide immunization services throughout the epidemic season. Pregnant women can receive inactivated influenza vaccine at any stage of pregnancy. These guidelines are intended for use by staff of CDCs, healthcare workers, maternity and child care institutions and immunization clinic staff members who work on influenza control and prevention. The guidelines will be updated periodically as new evidence becomes available.
Pregnancy ; Adult ; Infant ; Female ; Humans ; Adolescent ; Child, Preschool ; Influenza Vaccines ; Influenza, Human/prevention & control* ; Seasons ; COVID-19 ; COVID-19 Vaccines ; Pandemics ; Vaccination ; Vaccines, Attenuated ; Vaccines, Combined ; China/epidemiology*

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.
Humans ; Influenza Vaccines ; Influenza, Human/epidemiology* ; COVID-19 Vaccines ; COVID-19/prevention & control* ; Seasons ; Vaccination ; SARS-CoV-2

Since the global pandemic of COVID-19, different countries have implemented various prevention and control measures, which has affected the epidemic characteristics of respiratory infectious diseases such as influenza. From 2020 to 2021, the level of influenza activity was relatively low, but it is necessary to be alert that with the adjustment of national prevention and control measures, influenza may have a relatively strong epidemic rebound. In order to deal with influenza epidemic, experts were organized to publish a series of influenza studies in this issue, suggesting that influenza prevention and control cannot be underestimated during the COVID-19 pandemic. It is suggested to carry out research on the interaction between COVID-19 and influenza to explore the epidemic characteristics of the disease, develop new technologies and tools to improve the efficiency of monitoring and early warning, identify obstacles to vaccination, promote the scientific implementation of intervention measures, and achieve joint prevention and control of multiple diseases.
Humans ; Influenza, Human/prevention & control* ; COVID-19 ; Pandemics/prevention & control* ; Vaccination ; Communicable Diseases/epidemiology*

Objective: To analyze the epidemiological characteristics, etiology and hemagglutinin (HA) gene characteristics of prevalent strains in Shandong Province from 2021 to 2022. Methods: The sentinel surveillance data of influenza-like illness (ILI) were collected in Shandong Province from 2021 to 2022. ILI specimens were detected with Real-Time PCR and virus isolation to explore the distribution of influenza viruses in different months. Three virus strains of each city were selected for gene sequencing, and the HA phylogenetic analysis was carried out. Results: In the surveillance-year from 2021 to 2022, 528 263 ILI cases were totally reported in 54 sentinel hospitals for influenza surveillance in Shandong Province. ILI visiting ratio (ILI%) was 4.07%, with the largest number in 0-4 age group (45.86%). The highly frequent season for ILI was in winter and spring, with a peak in the 52nd week, 2021 (6.62%). Totally, nucleic acid was detected in 26 754 specimens, with a positive rate of 27.10%, all of which were type B Victoria influenza. The positive rate reached a peak in the 49th week, 2021 (63.78%). A total of 295 outbreaks of ILI had been reported, in which 269 were positive for influenza virus. Most of outbreaks occurred in the primary school, with a peak in December. Gene evolution analysis showed that the HA gene in Shandong possessed high homology, 98.6% to 99.5%, with the recommended vaccine strains in 2020-2023, which was divided into two branches, V1A.3a.1 and V1A.3a.2. Conclusion: In the surveillance-year of 2021-2022, influenza is prevalent in December in Shandong Province, with a single circulating strain type. The positive rate of influenza virus and outbreak are higher than those in the previous surveillance-year. The circulating strain possesses high HA gene homology with those of the WHO vaccine recommended strains. However, the overall immune barrier of influenza virus is weak.
Humans ; Influenza, Human/prevention & control* ; Phylogeny ; Influenza Vaccines ; Orthomyxoviridae ; Seasons ; China/epidemiology* ; Virus Diseases

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.
Child, Preschool ; Humans ; Aged ; Influenza, Human/prevention & control* ; Seasons ; Influenza Vaccines ; Vaccination ; China/epidemiology* ; Policy

Influenza is an acute respiratory infectious disease caused by influenza virus. It usually exhibits seasonal transmission, but the novel influenza strain can lead to a pandemic with severe human health and socioeconomic consequences. Early warning of influenza epidemic is an important strategy and means for influenza prevention and control. On the basis of reviewing the main influenza surveillance and early warning systems, this study summarizes the principles, applications, advantages and disadvantages, and development prospects of common influenza early warning models, in order to provide reference for research and application of early warning technology for influenza and other acute respiratory infectious diseases.
Humans ; Influenza, Human/epidemiology* ; Pandemics/prevention & control*

The avian influenza A (H7N9) virus is a zoonotic virus that is closely associated with live poultry markets. It has caused infections in humans in China since 2013. Five waves of the H7N9 influenza epidemic occurred in China between March 2013 and September 2017. H7N9 with low-pathogenicity dominated in the first four waves, whereas highly pathogenic H7N9 influenza emerged in poultry and spread to humans during the fifth wave, causing wide concern. Specialists and officials from China and other countries responded quickly, controlled the epidemic well thus far, and characterized the virus by using new technologies and surveillance tools that were made possible by their preparedness efforts. Here, we review the characteristics of the H7N9 viruses that were identified while controlling the spread of the disease. It was summarized and discussed from the perspectives of molecular epidemiology, clinical features, virulence and pathogenesis, receptor binding, T-cell responses, monoclonal antibody development, vaccine development, and disease burden. These data provide tools for minimizing the future threat of H7N9 and other emerging and re-emerging viruses, such as SARS-CoV-2.
Animals ; COVID-19 ; China/epidemiology* ; Humans ; Influenza A Virus, H7N9 Subtype ; Influenza in Birds/epidemiology* ; Influenza, Human/prevention & control* ; Poultry ; SARS-CoV-2

Influenza is a respiratory infectious disease that can seriously affect human health. Influenza virus has frequent antigenic drifts that can facilitate escape from pre-existing population immunity and lead to rapid and widespread transmission. Seasonal influenza is characterized by annual epidemics and outbreaks in places of public gathering such as schools, kindergartens, and nursing homes. According to the World Health Organization (WHO), seasonal influenza causes 3 to 5 million severe cases and 290 000 to 650 000 deaths globally each year. Pregnant women, young children, the elderly, and persons with chronic medical conditions are at highest risk for severe illness and death from influenza virus infection. With the ongoing COVID-19 pandemic, SARS-CoV-2 may co-circulate with influenza and other respiratory viruses in the upcoming winter-spring influenza season. Seasonal influenza vaccination is the most effective way to prevent influenza virus infection and complications from influenza. China has several licensed influenza vaccines - trivalent inactivated influenza vaccines (IIV3), which include split-virus influenza vaccine and subunit vaccine; quadrivalent split-virus inactivated influenza vaccine (IIV4); and trivalent live attenuated influenza vaccine (LAIV3). With the exception of a few major cities, influenza vaccine is a non-program vaccine, which means that influenza vaccination is not included in China's Expanded Program on Immunization, and recipients must pay for influenza vaccine and its administration. China CDC has issued "Technical Guidelines for Seasonal Influenza Vaccination in China" every year from 2018 to 2020. This past year, there have been scientific and programmatic advances in prevention and control of seasonal influenza. To strengthen technical guidance for prevention and control of influenza and facilitate operational research on influenza vaccination, the National Immunization Advisory Committee (NIAC) Influenza Vaccination Technical Working Group (TWG) updated the 2020-2021 technical guidelines into the "Technical Guidelines for Seasonal Influenza Vaccination in China (2021-2022)." The new version has updates in five key areas: (1) new research evidence, especially from studies in China, on disease burden, vaccine effectiveness, vaccine-avoidable disease burden, vaccine safety monitoring, and cost-effectiveness and cost-benefit analyses, (2) policies and measures for influenza prevention and control that were issued by National Health Commission (NHC) in the past year, (3) licensure of a new seasonal influenza vaccine in time for the 2021-2022 season, (4) composition of the northern hemisphere trivalent and quadrivalent influenza vaccines for the 2021-2022 season, and (5) recommendations for influenza vaccination during the 2021-2022 influenza season. The recommendations specify that immunization clinics should provide influenza vaccine to all persons aged 6 months and above who are willing to be vaccinated and do not have contraindications; the interval between receipt of influenza vaccine and COVID-19 vaccine should at least 14 days; and there is no preference for one influenza vaccine over another for persons for whom more than one licensed, recommended, and appropriate vaccine is available. Considering the global COVID-19 pandemic and the need to decrease risk of influenza virus infection and minimize potential impact on COVID-19 prevention and control, we recommend the following target population priorities in preparation for the 2021-2022 influenza season: (1) healthcare workers, including clinical doctors and nurses, public health professionals, and quarantine professionals, (2) volunteers and staff who provide service and support for large events, (3) people living in nursing homes or welfare homes and staff who take care of vulnerable, at-risk individuals, (4) people who work in high population density settings, including teachers and students in kindergartens, primary, and secondary schools and prisoners and prison staff, and (5) people with high risk of complications from influenza, including adults ≥60 years of age, children 6-59 months of age, persons with certain chronic conditions, family members and caregivers of infants <6 months of age, and pregnant women and women who plan to become pregnant during the influenza season. Children 6 months through 8 years of age who have never received influenza vaccine or who have received only one lifetime dose require 2 doses of influenza vaccine that are administered at least 4 weeks apart. This recommendation applies to both IIV and LAIV. If children received 2 doses of influenza vaccine in the 2020-2021 influenza season or received more than 2 doses of influenza vaccine in prior influenza seasons, 1 dose of influenza vaccine is recommended. People more than 9 years old require only 1 dose of influenza vaccine. People should receive influenza vaccination by the end of October, and influenza vaccine should be offered as soon as it is available. For people unable to be vaccinated before the end of October, influenza vaccine will continue to be offered throughout the season. Influenza vaccine is recommended for pregnant women during any trimester of pregnancy. These guidelines are intended for use by staff of CDCs at all levels who work on influenza control and prevention; immunization clinic staff members; healthcare workers from departments of pediatrics, internal medicine, and infectious diseases; and staff of maternity and child care institutions at all levels. The guidelines will be periodically updated as new evidence becomes available.
Aged ; COVID-19 ; COVID-19 Vaccines ; Child ; Child, Preschool ; China/epidemiology* ; Female ; Humans ; Infant ; Infant, Newborn ; Influenza, Human/prevention & control* ; Pandemics ; Pregnancy ; SARS-CoV-2 ; Seasons ; Vaccination

China experienced a very high and severe influenza seasonal epidemics during the past winter and spring of 2017-2018 season. This year of 2018 is the 100(th) anniversary of the 1918 "Spanish influenza" pandemic, a series of papers under the topic "One Hundred Years of Influenza Pandemics" are produced to demonstrate the impact, characteristics and responses of the past influenza pandemics in global and China, to review the progress and experiences of influenza surveillance, prevention and control strategies, vaccination and antivirus in China, and to discuss the gap and challenges of the prevention, control and response to the seasonal influenza, human avian influenza infection and influenza pandemics. We hope this series could help to raise the awareness of the seasonal and pandemic influenza in publics, and to improve the pandemic preparedness in China.
Animals ; Awareness ; Birds ; China/epidemiology* ; Humans ; Influenza Vaccines ; Influenza in Birds/prevention & control* ; Influenza, Human/prevention & control* ; Pandemics/prevention & control* ; Seasons ; Vaccination

Every influenza pandemic in history would end up with disastrous outcomes on mankind, of which the most notorious one was the "Spanish flu" pandemic in 1918. In the past century, with advanced knowledge on influenza viruses, laboratory technologies and surveillance methods, human beings were not as helpless when facing the influenza pandemic. In order to control the outbreaks and reducing the negative impacts, programs as: setting up and improving the influenza pandemic preparedness and response plan were recognized as important issues on early detection or prompt warning of any influenza virus strain that might lead to potential pandemics. The scheduled and planned control measures towards the pandemic preparedness and response plan had been considered of key importance in mitigating the peak of pandemic or controlling the transmission of virus. Since the "1918 influenza pandemic" , we had reviewed the evolution and development of plans regarding the preparedness and response on influenza pandemic issued by both WHO and China. We also emphasized on the variety of strategies which were linked to the preparedness and response at different historical stages, to provide reference for the pandemic preparedness of the disease, in the future.
China/epidemiology* ; Disease Outbreaks/prevention & control* ; Forecasting ; Humans ; Influenza A Virus, H1N1 Subtype ; Influenza, Human/virology* ; Pandemics/prevention & control*