1. A new hepatitis E vaccine tested in China was safe and provided protection from the virus for up to 4.5 years after vaccination.
Evidence Rating Level: 1 (Excellent)
Study Rundown: The hepatitis E virus, endemic to Asia, Africa, the Middle East and Central America, is a waterborne virus that causes acute hepatitis. It has a tendency to cause fulminant liver failure in pregnant women. The reasons underlying this association are not well known.
This study is an extended follow-up on a hepatitis E vaccine efficacy trial published in 2010. In the 2010 study, over 100,000 people in China were randomized to receive the recombinant protein-based vaccine or a placebo and were followed for one year. No cases of hepatitis E developed in the vaccine group, compared to 15 cases in the placebo group. The vaccine was licensed in China in 2011 under the name Hecolin.
This study extended the follow-up period to 54 months. Ultimately, there were 7 cases of hepatitis E in the vaccine group compared to 53 cases in the placebo group. Overall vaccine efficacy was 86.8% and did not decline appreciably over the course of the follow-up period. There were a similar number of adverse events between both the vaccine and placebo groups and none of the events were judged to be related to the vaccine itself.
It remains to be seen whether this vaccine is equally effective against all strains of hepatitis E (the most common strain in China and in this study was genotype 4) and whether the vaccine is equally safe and efficacious in children under 16.
In-Depth [randomized controlled trial]: This study of 112,604 healthy adults from 16 to 65 years of age in China evaluated the efficacy of a three-dose schedule for a recombinant hepatitis E antigen based vaccine. The vaccine was highly efficacious and safe, with no adverse events attributed to the vaccine and a vaccine efficacy of 86.8% in the modified intention-to-treat analysis.
The estimated prevalence of hepatitis E seropositivity at baseline in this cohort was 47%, implying that a large proportion of people in the study had already been naturally exposed to hepatitis E and were immune. Nevertheless, the vaccine was effective at increasing anti-hepatitis E antibodies in all participants, regardless of baseline serologic status.
The vaccine was most effective if all three doses were given. Among those who had never been exposed to hepatitis E, those receiving all three doses had higher levels of anti-hepatitis E antibodies compared to those receiving only one or two doses. Furthermore, the vaccine efficacy was 93.3% among those receiving all three doses compared to an efficacy of 86.8% when including all the participants that received only one or two doses.
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