Impact of kindergarten structures on the dynamics of hand, foot, and mouth disease and the effects of intervention strategies: an agent-based modeling study.

Background: Hand, foot, and mouth disease (HFMD) poses an unignorable threat to the health of kindergarten children. Kindergarten structures (i.e., class size and kindergarten size) may influence the transmission dynamics and the effectiveness of non-pharmaceutical interventions (NPIs), but few studies have explored these effects.

Methods: We developed an agent-based network model to study the effects of kindergarten structures on dynamics of HFMD caused by three types of strains (i.e., EV-A71, CVA16, and other EVs). We pursued a systematic review to collect data on HFMD outbreaks to estimate key model parameters. We simulated a series of scenarios to study the effects of NPIs (i.e., isolation of symptomatic individuals, class and family quarantine, and kindergarten closure, organized stepwisely), under different kindergarten sizes (n = 180, 360, and 900) and class sizes (m = 10, 20, 30, 60, etc.). We further explored alternative interventions combined with vaccination to avoid kindergarten closure during an outbreak.

Results: Overall, we found that the larger the class size, the more cumulative infections and the less effectiveness of NPIs in kindergartens. Stronger NPIs resulted in better effectiveness, and the variations in effectiveness among different class sizes gradually reduced with stronger interventions. Similar patterns were shown in kindergartens with small, medium, and large sizes. NPIs including kindergarten closure, which is implemented in many endemic countries, was a potent epidemic control strategy, capable of reducing cumulative incidence by over 80% for most class sizes in medium-size kindergartens. For EV-A71 infections, a vaccine coverage of 50% was alternative to kindergarten closure, when class size was 60 or less in medium-size kindergartens.

Conclusions: Kindergarten structures, particularly class size, had an important impact on dynamics of HFMD and effectiveness of NPIs within kindergarten. Increasing vaccination coverage may be an alternative to kindergarten closure for control of the disease.