Just two doses of vaccine would be enough to combat viral hepatitis E (HVE). This is what a study carried out by Médecins sans frontières (MSF) and the University of Geneva (Switzerland) suggests, in the journal The Lancet Infectious Diseases. The Hecolin vaccine, created and authorized since 2011 in China to fight against hepatitis E, normally includes a vaccination schedule of three injections, at 0, 1 and 6 months. The World Health Organization (WHO) has recommended its use since 2015 during a major wave of HVE.
"Waves of hepatitis E can sometimes last for years because of the difficult living conditions of these residents", explains to Science and Future Iza Ciglenecki, operational research coordinator at MSF Switzerland. Her study was carried out in Bentiu, South Sudan, a camp for displaced people, due to the civil war that has been raging in the country since 2013. In this place, access to hygiene or the establishment of water sanitation are compromised.
In addition, numerous floods, such as in 2021, make access to clean water even more difficult. Injecting three doses of vaccine is therefore, in practice, much more complicated to set up than it seems, "particularly because of the large number of population movements and the delay between the second and third doses, which is four months," adds Iza Ciglenecki.
What is hepatitis E?
L'hepatitis E (or HEV) is an infectious disease of the liver, caused by a virus, transmitted through contaminated water or food via the stools of infected people. According to the WHO, approximately 50,000 people die from it each year worldwide. In total, there are four different genotypes of hepatitis E. According to the Ministry of Health, genotypes 1 and 2 are more common in Asia, the Middle East, Africa, and India. Genotype 3 is responsible for approximately 200 to 300 cases per year in France and other industrialized countries. Hepatitis E is characterized by various symptoms: fever, jaundice, nausea, vomiting, abdominal pain, etc.
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Two doses are enough to obtain 89.4% of protection
Iza Ciglenecki and her colleagues therefore wanted to know if just two doses could be enough to protect the most vulnerable populations against this infectious virus. Thus, out of the approximately 100,000 people present in the camp, MSF carried out a vaccination campaign on 26,846 people (aged between 16 and 40 years old). In total, 86% of them received at least one dose of vaccine, 73% had two and only 58% had access to three injections of Hecolin. These figures show the difficulty of vaccinating the same people three times, and that it is simpler to inject them with only two doses, especially if they are as effective as three. According to Iza Ciglenecki, "The local population accepted to be vaccinated more easily than one would have thought, in fact hepatitis E is such a widespread disease that everyone there knows at least one person who has already been seriously affected or died because of hepatitis E".
Following this vaccination campaign, "the first to be made in the middle of a hepatitis E epidemic", Doctors Without Borders members found that just two doses were enough to protect vaccinated people by 89.4%, compared to 100% for three. However, although protection is somewhat reduced, especially in the long term, a two-dose vaccination schedule is still a good solution in crisis situations, "with a protective efficacy of at least six months (study time, editor's note)“ .
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Two-dose vaccine protects even at 89.9%, 10 years later
However, one question remains: are two doses of Hecolin enough to protect patients in the long term? To answer this question, during clinical trials conducted in China to test the Hecolin vaccine, researchers looked at the efficacy of the vaccine at two and three doses, at 30 months after the injection. and 10 years later. This research has shown that a classic three-dose regimen still demonstrates an efficacy of 100% several months and even 10 years later. Although two injections are less effective, they still protect patients to the tune of 89.9% at 30 months and 10 years after the vaccine. Furthermore, according to the operational research coordinator at MSF Switzerland, "Having already been exposed to the virus allows the vaccine to act as an immunity booster, making it even more effective during a wave of hepatitis E, particularly in Bentiu."
"Our study found that two doses of the vaccine were effective, an excellent result given the particular context of a camp for internally displaced people", concludes Iza Ciglenecki. Demonstrating that in the event of a crisis situation, two doses are a good solution for adapting to the real situation, to preserve populations, in the short and longer term.