Association of rBS-WC cholera vaccination with decreased infectious diarrhea incidence in Guangzhou city: spatial autocorrelation and BSTS model-based analysis on report data of 2015 – 2022

  Objective  To explore incidence characteristics of infectious diarrhea and the association of recombinant B-subunit/inactivated whole cell (rBS/WC) cholera vaccination with infectious diarrhea incidence in Guangzou city, Guangdong province.

  Methods  The data on reported infectious diarrhea cases and on rBS/WC cholera vaccination in Guangzhou city were extracted from Infectious Disease Monitoring and Reporting System and Immunization Planning Information Management System of Guangzhou Municipal Center for Disease Control and Prevention; the collected data were assigned into two datasets of different year period before (2015 – 2019) and after (2020 – 2022) the large-scale promotion on rBS/WC cholera vaccination. Relevant demographic data were obtained from municipal statistical yearbooks and the Seventh National Population Census. Community- and population group-specific annual and year period incidence of infectious diarrhea were calculated. ArcGIS10.8 was used to explore the spatial aggregation of infectious diarrhea incidence Guangzhou, and the effect of rBS/WC cholera vaccination on the incidence of infectious diarrhea was evaluated by using synthetic control method combined with Bayesian time series model (BSTS)-based counterfactual prediction method with R4.2.1 software.

  Results   During 2015 – 2022, the cumulative number of infectious diarrhea cases was 123 582 in the city. The average annual reported incidence (1/100 000) of infectious diarrhea decreased significantly from 91.84 during 2015 – 2019 to 77.48 during 2020 – 2022 (χ² = 13 891.686, P < 0.05). In terms of subgroup populations, there was no significant gender difference in year period-specific incidence before and after rBS/WC cholera vaccination, but the incidence changed significantly after the vaccine promotion among 0 – 2 years old children (χ² = 1 263.733) and community-dwelling children (χ² = 1 266.090) (both P < 0.05). The results of spatial autocorrelation analysis showed that there were spatial clusters in annual and year period infectious diarrhea incidence, with Moran′s I values of greater than 0 (all |Z| > 1.96, P < 0.05); the spatial clustering patterns of the incidence were basically consistent with the spatial configuration of BS/WC cholera vaccination level. The BSTS model analysis revealed a deficit ratio of 37.18% (95% confidence interval: 13.81% – 60.07%) between the predicted and observed number of infectious diarrhea incidence for the period of 2020 – 2022 with large-scale promotion of rBS/WC cholera vaccination and the deficit differed by age and daily activities of subgroup populations, suggesting a possible protective effect of rBS/WC cholera vaccination against infectious diarrhea caused by other pathogens.

  Conclusion  The decrease and the variation in spatial and population clustering of infectious diarrhea incidence may associate with large-scale promotion of rBS/WC cholera vaccination in Guangzhou city.