Longitudinal Population-Level Shifts in Infectious Disease-Specific Health Literacy During and After the COVID-19 Pandemic in Zhejiang, China: Six-Round Cross-Sectional Study.

Background: Infectious disease-specific health literacy (IDSHL)-the capacity to obtain, process, and understand basic infectious disease information needed to make appropriate health decisions-is a critical determinant of public health outcomes. The COVID-19 pandemic created an unprecedented global public health education context; yet, its long-term association with population-level IDSHL beyond the pandemic remains unclear. In China, stringent public health measures and digital information campaigns were implemented, yet their lasting impact on IDSHL across different disease domains has not been systematically evaluated over a full pandemic cycle. Objective: This study aimed to evaluate the longitudinal trends in IDSHL among residents of Zhejiang Province, China, from 2019 (prepandemic) to 2024 (postpandemic), and to assess whether the pandemic period was temporally associated with sustained improvements in IDSHL. Methods: Six annual cross-sectional surveys were conducted from 2019 to 2024 across 30 counties in Zhejiang Province using consistent multistage stratified random sampling. A validated 12-item IDSHL questionnaire assessed knowledge, behavior, and skills. Annual sample sizes ranged from 17,131 to 19,257 (N=112,917). Data were weighted to the 2020 census population by age and urban or rural residence. Joinpoint regression identified inflection points in the annual proportion of residents with adequate IDSHL (score≥12). Multivariate logistic regression estimated adjusted odds ratios (ORs) for adequate IDSHL by year, with 2021 as the reference (the peak acute pandemic phase), controlling for sociodemographics. All analyses incorporated sampling weights. Results: Population-weighted overall IDSHL scores increased from 2019 (mean 10.46 SD 3.09) to 2024 (mean 11.40 SD 2.88; P<.001). All subscale scores (knowledge, behavior, and skills) showed upward trends (all P<.001). Joinpoint regression revealed a rapid annual increase in adequate IDSHL during 2019-2021 (annual percent change 9.42%, 95% CI 6.10-13.45; P<.001), which slowed post-2021 (annual percent change 2.28%, 95% CI -0.38 to 3.73; P=.07). Correct response rates surged for pandemic-salient items (eg, respiratory etiquette from 28.44% to 39.67%), while hepatitis B transmission knowledge fluctuated (63.28% in 2019, 60.71% in 2022, 63.84% in 2024), indicating that not all non-COVID-19 content improved monotonically. Adjusted logistic regression showed the lowest odds of adequate IDSHL in 2019 (OR 0.74, 95% CI 0.71-0.78) and highest in 2024 (OR 1.10, 95% CI 1.05-1.15) compared to 2021. Conclusions: The COVID-19 pandemic was temporally associated with significant and sustained population-level improvements in IDSHL, particularly for pandemic-relevant knowledge and behaviors. However, gains were time-sensitive and not uniform across all disease domains or demographic groups. These findings underscore the need for postpandemic health strategies that reinforce comprehensive IDSHL through sustained education and address digital divides to bridge persistent equity gaps. Policymakers should prioritize low digital-literacy populations through hybrid (offline+online) educational interventions, and sustain routine surveillance of IDSHL to detect declines in nonpandemic disease knowledge. This study is the first to document six-year population-level IDSHL trends across the full pandemic cycle, providing evidence for future crisis communication and routine health promotion.