Previously submitted to: JMIR Public Health and Surveillance (no longer under consideration since Jun 10, 2024)
Date Submitted: Sep 25, 2023
Open Peer Review Period: Sep 24, 2023 - Oct 8, 2023
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Differences in symptoms and clinical outcomes of COVID-19 infection across vaccination status and age groups: a cross-sectional study of 2350 adults during the national pandemic from December 2022 to February 2023 in China
ABSTRACT
Background:
China had been implementing national anti-COVID measures until ending the ‘dynamic zero-COVID’ policy in 7 December 2022. Studies assessing the difference in clinical outcomes across vaccination status and age groups for the recent massive national COVID-19 outbreak in China are limited.
Objective:
We aimed to evaluate the associations between vaccination status, age groups and clinical outcomes in Chinese adults.
Methods:
This was a nationwide retrospective survey study conducted from January to February 2023 in Chinese adults. Information on COVID-19 infection status since December 2022, symptoms, COVID-related clinic visits, hospital admission, doses of vaccines received were collected by online survey or phone interview. Data were analyzed by log-binomial regression, negative binomial regression and ordered logistic regression.
Results:
Of 2350 participants aged 18-98 years, 81% were infected or probably infected, 78% had received ≥ 2 doses of vaccine. Vaccination rate decreased with age. Compared to young adults, older adults (aged above 75 years) were more likely to have fatigue, had longer length of time to symptom disappearance, higher chance of having pneumonia, higher prevalence of clinic visit and hospitalization. Adjusting for multimorbidity significantly reduced the effect sizes. Compared to unvaccinated group, receiving ≥ 3 doses was associated with significant lower chance of having pneumonia (OR 0.580, 0.411 to 0.819) and lower prevalence of clinic visits (PR 0.629, 0.488 to 0.810) and hospitalization (PR 0.293, 0.162 to 0.530).
Conclusions:
During this massive Omicron outbreak in China, older adults remain at higher risk for negative clinical outcomes and multimorbidity partially explained the increased risk. Receiving vaccines seems protect against adverse clinical outcomes. The government need to continue promoting vaccination in older adults to mitigate the potential health service burden related to COVID-19 infection. Clinical Trial: NA
Citation
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