Two-dose regimen of vaccine offers substantial protection against Hepatitis E Outbreak, suggests study

A new study conducted during the first-ever reactive use of the Hecolin vaccine in South Sudan showed that a two-dose regimen of the vaccine offers substantial protection against Hepatitis E. The findings published in The Lancet Infectious Diseases suggested that the two-dose Hecolin vaccine could be a viable option for controlling outbreaks in resource-limited settings.

Hepatitis E is a major cause of acute viral hepatitis which disproportionately affects regions like Asia and Africa where genotypes 1 and 2 of the virus are prevalent. Despite a 3-dose recombinant vaccine (Hecolin) being licensed, its deployment during outbreaks has underwent logistical challenges due to the extended vaccination schedule. This study brings out the effectiveness of a shorter, two-dose regimen.

This case-control study was conducted during an outbreak from May to December 2022 in the Bentiu IDP camp. The study focused on individuals aged 16 to 40 years who were eligible for vaccination. Acute jaundice syndrome cases were screened, and confirmed hepatitis E cases were identified using RT-PCR or anti-HEV IgM ELISA testing. Each case was matched with 6 controls based on age, sex, pregnancy status, and residence. Vaccination status was verified through vaccination cards.

Of the total 859 suspected hepatitis E cases screened, 201 met the study criteria, and 21 were laboratory-confirmed as positive for the virus. Among confirmed cases, 48% were unvaccinated when compared to only 27% of their matched controls.

The key findings from the study revealed that the unadjusted two-dose vaccine effectiveness was around 67.8%. The effectiveness increased to 84% after adjusting for potential confounders. A secondary analysis using a test-negative design estimated the adjusted vaccine effectiveness to be as high as 89.4%. This method also addressed potential biases in health-care-seeking behaviors, which could underestimate vaccine efficacy.

While the sample size of the study was small, the findings indicate that the two-dose regimen of Hecolin offers robust protection against Hepatitis E genotype 1, with effectiveness estimates ranging between 84% and 89%. This provides strong data to support the use of a shorter vaccination schedule during outbreaks, especially in protracted emergency settings like the Bentiu camp. Also, this study pointed to the need for further research to optimize outbreak response strategies but provides a hopeful step toward controlling Hepatitis E in vulnerable populations.

Reference:

Nesbitt, R. C., Kinya Asilaza, V., Alvarez, C., Gitahi, P., Nkemenang, P., Duncker, J., Haile, M., Gakima, P., Wamala, J. F., Loro, F. B., Koyuncu, A., Biem, D., Albela, M., Rull, M., Gignoux, E., Rumunu, J., Eckerle, I., Ciglenecki, I., & Azman, A. S. (2025). The effectiveness of two doses of recombinant hepatitis E vaccine in response to an outbreak in Bentiu, South Sudan: a case–control and bias indicator study. The Lancet Infectious Diseases. https://doi.org/10.1016/s1473-3099(24)00657-1