Vaccination coverage survey of children aged 1-3 years in Beijing, China, 2005-2021.

Background: The routine immunization program for children is a primary strategy and a core part of vaccination. Achieving and maintaining high level of vaccination coverage are important to reduce morbidity and mortality caused by vaccine-preventable diseases. In Beijing, annual coverage surveys have been conducted since 2005. It is necessary and possible to assess the level and trend of routine vaccination coverage of children in Beijing as well as the disruption of coronavirus disease 2019 (COVID-19) pandemic and provide the reference for the further improve the vaccination coverage.

Methods: The data of 61,521 children aged 1-3 years in the vaccination coverage surveys during 2005-2021 were analyzed by Beijing Center for Disease Control and Prevention. Descriptive epidemiological method was used to analyze the data and the difference of vaccination coverage within the time period.

Results: More than 99 % of participants had immunization cards and electronic immunization records. The concordance rate of both records were also over 99 %. During 2011-2019, the rates of on-time and in-time vaccination of each routine vaccine reached 96 % or more and increased significantly (all P values <0.05), compared with that of 2005-2010. All rates of the investigated vaccine, except for Bacillus Calmette-Guérin vaccine (BCG) and the first dose of hepatitis B vaccine (HepB), decreased in 2020-2021 significantly (all P values <0.05). For the causes of failing to vaccinate on time, delayed vaccination accounted for 47.82 %. The top two vaccines to be missed were the first dose of hepatitis A vaccine and the 4th dose of diphtheria-tetanus-acellular pertussis vaccine, accounting for 21.41 % and 20.79 %, respectively. The main reason for zero-dose/drop-out vaccination was "Guardians regarded the immunization service time as inappropriate", accounting for 72.27 %.

Conclusion: The coverage level and service quality of routine immunization in Beijing were relatively high. However, as influenced by COVID-19 epidemics, both on-time and in-time vaccination rates decreased significantly, except for BCG and HepB. Under the background of COVID-19 pandemic, the keys to maintain high level of vaccination coverage include flexible immunization service time to ensure the guardians bringing their children for vaccination timely, and more attention from providers to the doses after children's first birthday.