Ongoing Epidemiological Changes in Hand, Foot, and Mouth Disease Following the Introduction of Enterovirus 71 Vaccines in Yunnan Province, China, 2008-2019

Background: Since 2016, enterovirus 71 (EV71) vaccines have been approved for market entry, and litter is known about how the epidemiology of hand, foot, and mouth disease (HFMD) has been affected by the introduction of the vaccines in Yunnan Province. The study describes the ongoing epidemiological changes in HFMD following the introduction of EV71 vaccination in Yunnan. Methods: : Surveillance data collected between 2008 and 2019 were analyzed to produce EV71 vaccination coverage, epidemiological distribution on cases, and etiologic composition as well as to compare these characteristics before and after EV71 vaccination. Results: : A total of 1,653,533 people received EV71 vaccines from 2016 through 2019 in Yunnan. The cumulative EV71 vaccination coverage rate was 68.14%. After the introduction of EV71 vaccines, the overall incidence of HFMD increased and reached over 200 cases per 100,000 population-years in 2018 and 2019. However, the case severity and case fatality rate decreased and remained lower than 1% and 0.005% after 2016, respectively. EV71-associated mild, severe and fatal cases sharply decreased. The predominant viral serotype changed to non-EV71/non-CV-A16 enteroviruses which were detected across the whole province. Conclusions: : EV71 vaccination helped to reduce severe HFMD. However, other enteroviruses became the predominant strain and let to a higher incidence. Expanding EV71 vaccination and strengthening laboratory-based surveillance could further decrease the burden of severe HFMD and reveal the existence of emerging enteroviruses.