[Prevalence and influencing factors of severe respiratory infections in childhood among residents of China, 2019-2020].

<b>Objective:</b> To analyze the exposure level and changes in severe respiratory infection among Chinese residents aged ≥40 years in China and to provide essential data for preventing and controlling chronic respiratory diseases. <b>Methods:</b> The data came from chronic obstructive pulmonary disease surveillance of Chinese residents in 2014-2015 and 2019-2020. The surveillance covers 31 provinces (autonomous regions and municipalities) in China. A multi-stage stratified cluster random sampling method was used to select permanent residents aged ≥40 years. Relevant information about exposure to severe respiratory infections during childhood was collected through investigation. Rigorous complex sampling and weighted analysis were applied to estimate the exposure rate of severe respiratory infections among children with different characteristics among residents aged ≥40 years in China from 2019 to 2020. Additionally, changes in severe respiratory infections during childhood were analyzed over 2014-2015 and 2019-2020. <b>Results:</b> In 2019-2020, the exposure rate of severe respiratory infection before 18 for residents aged ≥40 years in China was 21.58‰ (95%<i>CI</i>: 17.57‰-25.59‰). The exposure rate of severe respiratory infection before the age of 14 was 19.40‰ (95%<i>CI</i>:15.25‰-23.55‰), the difference in the exposure rate between men and women was not statistically significant (both <i>P</i>>0.05), and the exposure rate of urban residents is higher than that of rural residents. The results of multivariate logistic regression analysis showed that in western rural areas, factors including being born by cesarean section, exposure to secondhand smoke before age 14 years old, and a family history of chronic respiratory diseases were associated with severe respiratory infections in childhood. Compared with 2014-2015, the proportion of residents aged 40 and older in China hospitalized for pneumonia or bronchitis before 14 from 2019 to 2020 was slightly lower than five years prior. <b>Conclusions:</b> Among residents in China aged ≥40 years, 21.58‰ experienced severe respiratory infection exposure during childhood, varying exposure levels across different demographic groups. The burden of chronic respiratory diseases in adulthood cannot be ignored. Efforts should be made to expand the coverage of planned immunization and to focus on early-life interventions during childhood to reduce the incidence of severe respiratory infections.