The burden of dengue in children and risk factors of transmission in nine districts in Sri Lanka

We sought to understand the differences in age-stratified seroprevalence rates in different regions in Sri Lanka to plan dengue vaccination programs, especially as the WHO has given guidance to vaccinate in high transmission settings. Age stratified seroprevalence rates were assessed in children, aged 10-20 years, in nine districts representing the nine provinces in Sri Lanka, from September 2022 to March 2023. A stratified multistage cluster was used to select 146 schools representing each district. Of the 5207 children recruited, the overall dengue seroprevalence rates in children was 24.8%, with the highest rates reported from Trincomalee (54.3%) and the lowest rates from Badulla (14.2%), which is a high-altitude estate area. While the age-stratified seroprevalence rates increased in some districts such as Trincomalee, Jaffna, Gampaha, and Ratnapura, which reported the highest seropositivity rates, there was no such increase with age in the other districts. There was a weak correlation between the dengue antibody positivity rates and age in most districts which had seroprevalence rates of >25%, while there was no increase in antibody titers with age in the other districts. The seroprevalence rates was significantly higher in urban areas (35.8%) compared to rural (23.2%) and estate areas (9.4%), although there was no association with seropositivity rates with population density (Spearman's r = -0.01, p = 0.98), in each district. The seroprevalence rates in many districts were very different to those reported from Colombo, with many districts reporting low transmission rates. These data would be important to consider when rolling out dengue vaccines in Sri Lanka.