[Technical guidelines for seasonal influenza vaccination in China (2022-2023)]

Influenza is an acute respiratory infectious disease 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. SARS-CoV-2 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.