OBJECTIVES:

China eased its zero-COVID policy in November 2022 and then pandemic outbreak has imposed a substantial burden. This study aims to provide real-world evidence regarding vaccination and infection status among COVID-19 infection-naive individuals in China and to examine the vaccination effectiveness.

METHODS:

A retrospective online questionnaire survey was conducted in Beijing, China, from January 13th to February 9th, 2023 and a total of 45,344 eligible respondents were included in the analysis. Vaccination and infection status among different groups classified by age (under 18, 18-59, and over 60) and high-risk health conditions (having underlying disease, allergy, cancer, immune deficiency or organ transplant) were analyzed. Propensity score matching and ordered logistic regression were used to examine the effectiveness of different COVID-19 vaccine types (inactivated, adenovirus, subunit protein, and mRNA vaccine) and vaccination strategies (uncompleted vaccination, basic procedure, homogenous booster, and heterogenous booster).

RESULTS:

Vaccination rate among all respondents was 94.70%, with 23.73% of residents completed basic immune vaccination, 68.54% completed homogenous booster vaccination and 2.43% completed heterogenous booster vaccination; however, the high-risk population had a lower vaccination coverage. The overall infection and reinfection rates were 82.42% and 0.85%. Results showed that homogenous (OR=0.89) and heterogenous (OR=0.77) booster vaccinations were significantly associated with lower infection severity, and the elderly group benefited the most. No significant differences were observed among different vaccine types.

CONCLUSIONS:

Omicron infection rate among COVID-19 infection-naive individuals is extremely high. Booster vaccination can effectively prevent infection progression, particularly among elderly individuals. High-risk and vulnerable groups have lower vaccination rates, underscoring the need to improve vaccination coverage and prioritize regular booster vaccinations for them.