Originally published by 2 Minute Medicine® (view original article). Reused on AccessMedicine with permission.

1. EV71vac showed a vaccine efficacy of 96.8% against EV71-associated diseases.

2. Majority of adverse events were mild and self-limited with no hospitalizations or mortalities in the EV71vac group.

Evidence Rating Level: 1 (Excellent)

Study Rundown:

Enterovirus 71 (EV71) is a single-stranded RNA responsible for causing hand, foot, and mouth disease (HFMD) in children. Although most EV71 infections are benign, some may lead to serious consequences. Preventative management for EV71 includes vaccines; however, these work on a specific genotype and are only effective for children aged 6-35 months. This randomized controlled trial aimed to assess the safety, efficacy, and immunogenicity of EV71 vaccine (EV71vac) – an inactivated whole virus vaccine – in children aged 2-71 months. The primary outcome was overall efficacy of EV71vac, assessed at two weeks after the second dose, while key secondary outcomes included EV71-related hospitalizations and deaths. According to study results, EV71vac yielded a high efficacy against EV-related diseases, with minimal side effects. All laboratory-confirmed cases of EB71-associated disease in this study occurred in the placebo group. While this study was well done, it did not consider participants’ socioeconomic status which is a major factor in determining the prevalence and severity of enterovirus infections.

In-depth [randomized-controlled trial]:

Between Apr 23 and Dec 25, 2019, 3664 patients were assessed for eligibility across multiple hospitals in Taiwan and Vietnam. Children were randomly assigned to two doses of EV71vac or placebo (1:1) with 56 days in between both doses. Altogether, 2959 patients (1483 in placebo and 1476 in EV71vac) were included in the efficacy analysis. In the EV71vac group, adjusted vaccine efficacy was 96.8% (95% confidence interval [CI] 85.5-100.0, p<0.0001). The incidence rate per 1000 person-years was substantially higher in the placebo group (11.15, 95% CI 7.34-16.94) than EV71vac (0.00, 95% CI 0.00, p<0.0001). The secondary outcome of EV71-related complications was slightly greater in the placebo group (4 hospitalizations and 0 deaths) than EV71vac (0 hospitalizations and deaths). Moreover, most adverse events were mild-to-moderate in nature with a similar prevalence in either group (55.8% in placebo vs. 56.9% in EV71vac). Overall, findings from this study suggest that EV71vac is safe and effective in preventing EV71-related diseases in children aged 2-71 months.

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