Enterovirus A71 vaccine effectiveness in preventing enterovirus A71 infection among medically-attended hand, foot, and mouth disease cases, Beijing, China

Introduction: Enterovirus A71(EV-A71)-associated hand, foot, and mouth disease (HFMD) has been reported worldwide, and poses a particularly heavy burden on patients, families, and society in China. Three Chinese companies have licensed inactivated EV-A71 vaccines, all of which have demonstrated good efficacy for preventing EV-A71-associated disease in clinical trials. However, real-world performance of EV-A71 vaccine has not been evaluated. Methods: We used a test-negative design case-control study to estimate vaccine effectiveness (VE) against medically attended EV-A71-associated HFMD. Subjects were children 5 years of age and under who had been in health facilities participating in the HFMD case and virologic surveillance platforms in Beijing. Enterovirus infections were laboratory confirmed, and EV-A71 vaccination status was extracted from electronic immunization records. Children testing positive for EV-A71 were cases; controls were children testing negative for EV-A71 infection. Logistic regression was used to estimate VE. We assessed sensitivity of VE estimates to control group inclusion criteria by repeating the regression analyses with two alternative control groups. Results: A total of 2,184 HFMD patients aged 5 years and under were enrolled in the study; 24 were severe, and 2,160 were mild. For severe cases, two-dose VE estimate was 100% (95% CI: −68.1%, 100%). For mild cases, 1-dose and 2-dose adjusted VE estimates were 69.8% and 83.7%, respectively. Two-dose VE estimates varied by less than 4 percentage points regardless of control group definition. Conclusions: Our findings suggested the vaccines performed well in the real world for children 5 years of age and under in Beijing, China.