[Technical guidelines for seasonal influenza vaccination in China (2020-2021)].

Influenza virus infection is a respiratory infectious disease that can seriously affect human health. Influenza viruses can have frequent antigenic variation and changes, which can result in rapid and widespread transmission resulting in annual epidemics and outbreaks in places of public gathering such as schools, kindergartens and nursing homes. According to WHO estimation, seasonal influenza epidemics have caused an annually 3 to 5 million severe cases and 290 000 to 650 000 deaths globally. Pregnant women, young children, the elderly, and persons with chronic illnesses are at high risk for severe illness and death associated with influenza virus infection. Especially, COVID-19 pandemic might co-circulate with other respiratory infectious diseases such as influenza in the coming winter-spring season. Seasonal influenza vaccination is the most effective way to prevent influenza virus infection and complications from infection. Currently, China has licensed trivalent inactivated influenza vaccine (IIV3) which includes split-virus influenza vaccine and subunit vaccine, quadrivalent inactivated influenza vaccine (IIV4) which is split, and trivalent live attenuated influenza vaccine (LAIV3) which was newly licensed. Except for a few major cities, influenza vaccine is a category Ⅱ vaccine, which means influenza vaccination is voluntary, and recipients must pay for it. In 2018 and 2019, the China CDC issued the "Technical Guidelines for Seasonal Influenza Vaccination in China" . In the past year, new research evidences home and abroad have been published, and new seasonal influenza vaccine has been licensed in China. To strengthen the technical guidance for prevention and control of influenza and operational research on influenza vaccination in China, the National Immunization Advisory Committee (NIAC) Influenza Vaccination Technical Working Group (TWG), updated the 2019-2020 technical guidelines and compiled the "Technical guidelines for seasonal influenza vaccination in China (2020-2021)" . The main updates in this version include the following: First, new research evidences especially studies of China, including disease burden, effectiveness, Vaccine-avoidable disease burden, vaccine safety monitoring, and cost-effectiveness and cost-benefit. Second, policies and measures for influenza prevention and control issued by National Health Commission (PRC) in the past year. Thirdly, new type seasonal influenza vaccine licensed and issued in 2020-2021 in China. Fourth, northern hemisphere influenza vaccination composition for the 2020-2021 season which included trivalent and quadrivalent influenza vaccine. Fifth, Influenza vaccination recommendations for 2020-2021 influenza season. The recommendations described in this report include the following: Points of Vaccination clinics (PoVs) should provide influenza vaccination to all persons aged 6 months and above who are willing to be vaccinated and do not have contraindications. No preferential recommendation is made for one influenza vaccine product over another for persons for whom more than one licensed, recommended, and appropriate product is available. Considering the situation of globally pandemic of COVID-19, to decrease the risk of influenza virus infection and minimize the impact on COVID-19 prevention and control, we recommend the following priority for seasonal influenza vaccination: healthcare workers, including clinical doctors and nurses, public health professionals, quarantine professionals; vulnerable groups living in nursing homes or welfare homes and staffs who take care those vulnerable groups; people work or stay in high population density places, such as teachers and students in kindergartens, primary and secondary school, prisoners and staffs of prisons; other high risk group of influenza, including adults ≥60 years of age, children aged 6-59 months, persons with specific chronic diseases, the family members and caregivers of infants <6 months of age, and pregnant women or women who plan to become pregnant during the influenza season. Children aged 6 months through 8 years require 2 doses of influenza vaccine administered a minimum of 4 weeks apart during their first season of vaccination for optimal protection. People whoever get IIV or LAIV all apply to the principle. If they were vaccinated in 2019-2020 influenza season or a prior season, 1 dose is recommended. People more than 8 years old require 1 dose of influenza vaccine. It is recommended that people receive their influenza vaccination by the end of October. Influenza vaccination should be offered as soon as the vaccination is available. For the people unable to be vaccinated before the end of October, influenza vaccination will continue to be offered for the whole season. Influenza vaccine is also recommended for use in pregnant women during any trimester. These guidelines are intended for use by staff members of the CDCs at all levels who work on influenza control and prevention, PoVs staff members, healthcare workers from the departments of pediatrics, internal medicine, and infectious diseases, and staff members of maternity and child care institutions at all levels. These guidelines will be updated periodically as new evidence becomes available.