The changes in the epidemiology of hand, foot, and mouth disease after the introduction of the EV-A71 vaccine.

Three inactive monovalent EV-A71 vaccines have been launched in China since 2016, which may change the HFMD pathogen spectrum and epidemiological trend. Using notifications from the national surveillance system, we analyzed the epidemiological character profiles and the possible pathogen replacement. The proportion of HFMD cases aged 0-12 months decreased from 23.0% to 15.3% between 2013-2015 and 2017-2019 (p < 0.01). EV-A71 among laboratory-confirmed severe cases in 2013-2015 (62.8%) transformed to other EVs (67.2%) in 2017-2019. The age distribution of EV-A71 infection shifted to the older. The cumulative coverage of the EV-A71 vaccine for children aged six months to five years in Guangxi has increased, while in severe cases, the positive rate declined. After gradually expanded vaccination, EV-A71 associated incidence rate, case-severity rate has decreased, and other serotypes are becoming dominant. Thus, bivalent even polyvalent vaccines are urgently needed to control HFMD.

Effectiveness of enterovirus A71 vaccine in severe hand, foot, and mouth disease cases in Guangxi, China.

BACKGROUND: Hand, foot, and mouth disease (HFMD) caused by enterovirus A71 (EV-A71) is a major public health issue in China that poses severe risks to children's health, especially those under the age of 3. Since 2016, EV71 vaccines developed by three Chinese manufacturers have been approved for use, and clinical trials of these vaccines have demonstrated protection against EV-A71 infection. However, few studies have assessed the effectiveness of these vaccines in real-world settings. METHODS: A test-negative design case-control study was used to estimate vaccine effectiveness (VE) in cases of severe HFMD. We obtained information including EV-A71 vaccination status from the Local Center for Disease Control and Prevention (CDC) on all severe HFMD cases under 12 years in age in Guangxi, China, from Jan. 1, 2017, to Dec. 31, 2018. Enterovirus infection was laboratory confirmed by local CDCs. Individuals with a positive EV-A71 nucleic acid test result were assigned to the case group, and those with negative EV-A71 nucleic acid test results were assigned to the control group. We estimated VE using logistic regression. RESULTS: A total of 2779 severe HFMD cases were enrolled in the study; 838 children were EV-A71 positive cases, and 1941 children were EV-A71 negative controls. The proportion of EV-A71 positive cases aged 6-36 months was lower than that for EV-A71 negative controls. EV-A71 infection was associated with an increased risk of mortality (aOR, 8.8; 95% CI, 1.3-61.6). The adjusted VE was 81.4% and 88.3% for one dose and two doses, respectively. CONCLUSION: Our findings suggest that the rate of EV-A71 has fallen among severe HFMD cases in Guangxi and that the risk for EV-A71 infection in 6-36-month-old children has been reduced by use of the vaccine. Inactivated vaccines performed well in severe HFMD cases in a real-world setting.