Epidemiological Trends of COVID‐19 Infection and Symptom Incidence in China Following the Adjustment of Zero‐COVID Policy: A Prospective, Community‐Based Cohort Study

As one of the final countries to modify its zero-COVID policy, China’s population presented a unique cohort largely unexposed to COVID-19 for almost the first three years of the pandemic. This study tracked the post-adjustment infection rates and symptom trends within community settings. Conducted from May 2023 to May 2024 across four districts in Shenzhen, employing multi-stage stratified cluster sampling. Of 3,246 participants, 56.2% were female, with an average age of 39.7 years; over 80% had received at least one vaccine dose. Post-policy adjustment witnessed three significant infection surges, with infection rates at 63.7% for first-time, 30.3% for second-time, and 1.7% for third-time infections. 24.4% of infected individuals had a re-infection within 365 days of their first infection, and 4.9% had a re-infection within 365 days of their second infection. Older adults and those with lower IgG levels had increased reinfection risk. Notably, 3.8% reported Long COVID, with higher susceptibility in those with underlying conditions (Adjusted OR [AOR]=3.73, 95% CI: 2.20-6.34) and reduced incidence among fully vaccinated individuals (AOR=0.57, 95% CI: 0.36-0.90). The policy change led to widespread exposure, shifting from first infections to reinfections. These insights underscore the need for ongoing research to inform future pandemic responses. The study was approved by the Shenzhen Center for Disease Control and Prevention Ethics Committee (Ethics ID: 2023027A).