Key result
The inactivated EV71 vaccine maintained a high seroconversion rate of 98.1% at 2 years post-immunization and demonstrated protective efficacy with zero cases of EV71 infection in the vaccinated per-protocol group.
Why the study?
Does an inactivated EV71 vaccine prevent EV71 infection and maintain long-term immunity in healthy children?
RCT (n=1,100)
Double-blind
Randomly assigned in a 1:1 ratio
Yes
Does an inactivated EV71 vaccine prevent EV71 infection and maintain long-term immunity in healthy children?
The inactivated EV71 vaccine induces sustained immune responses and provides clinical protection against EV71 infection for at least 2 years in children.
Answers are grounded in this paper and cite their sources.
Supports EV71 vaccination in children; extends RCT evidence of durable protection to 2 years.
BACKGROUND: To investigate the long-term effects on immunity of an inactivated enterovirus 71 (EV71) vaccine and its protective efficacy. METHODS: A sub-cohort of 1,100 volunteers from Guangxi Province in China was eligible for enrolment and randomly administered either the EV71 vaccine or a placebo on days 0 and 28 in a phase III clinical trial and then observed for the following 2 years with approval by an independent ethics committee of Guangxi Zhuang Autonomous Region, China. Serum samples from the 350 participants who provided a full series of blood samples (at all the sampling points) within the 2-year period were collected. Vaccine-induced immune effects, including the neutralizing antibody titres and cross-protection against different genotypes of EV71, were examined. This study also evaluated the protective efficacy of this vaccine based upon clinical diagnosis. RESULTS: This sub-cohort showed a >60% drop-out rate over 2 years. The seroconversion rates among the 161 immunized subjects remained >95% at the end of study. The geometric mean titres of neutralizing antibodies (anti-genotype C4) 360 days after vaccination in 350 subjects were 81.0 (subjects aged 6-11 months), 98.4 (12-23 months), 95.0 (24-35 months), and 81.8 (36-71 months). These titres subsequently increased to 423.1, 659.0, 545.0, and 321.9, respectively, at 540 days post-immunization (d.p.i.), and similar levels were maintained at 720 d.p.i. Higher IFN-γ/IL-4-specific responses to the C4 genotype of EV71 and cross-neutralization reactivity against major EV71 genotype strains were observed in the vaccine group compared to those in the placebo group. Five EV71-infected subjects were observed in the placebo-treated control group and none in the vaccine-immunized group in per-protocol analysis. CONCLUSION: These results are consistent with the induction of dynamic immune responses and protective efficacy of the vaccine against most circulating EV71 strains. TRIAL REGISTRATION NUMBER: Clinicaltrials.gov, NCT01569581, Trial registration date: March 2012.
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Liu et al. (2015) conducted an RCT in Healthy children (prevention of enterovirus 71 infection) (n=1,100). Inactivated enterovirus 71 (EV71) vaccine vs. Placebo was evaluated on Seroconversion rate at 720 days post-immunization (p=<0.0001). The inactivated EV71 vaccine maintained a high seroconversion rate of 98.1% at 2 years post-immunization and demonstrated protective efficacy with zero cases of EV71 infection in the vaccinated per-protocol group.
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