Researchers from the Enteric Virus Research Group of the University of Barcelona (UB) have analyzed for the first time with massive sequencing techniques the evolution of the hepatitis A virus from patient samples. The results, published in the journal https://doi.org/10.1016/j.ebiom.2018.11.023" EBioMedicine, show the presence of variants of the virus that could escape the effects of the vaccine. The work, carried out in collaboration with the Vall d'Hebron Institute of Research (VHIR) and the Public Health Agency of Barcelona (ASPB), may have implications for vaccination policies against this disease.The article counts on the participation of Dr. Tomás Pumarola, head of the Microbiology research group at VHIR, head of the Microbiology Service and Director of Teaching at Vall d'Hebron, Josep Quer, principal investigator of the Hepatic Diseases group of the VHIR and of the CIBER of hepatic and digestive diseases (CIBERehd), Josep Gregori and Damir García-Cehic, researchers of the Hepatic Diseases group of the VHIR. And, on the part of the Department of Genetics, Microbiology and Statistics of the Faculty of Biology of the UB, the teachers Aurora Sabrià, Albert Bosch, Susana Yeso and Rosa Maria Pintó.Hepatitis A virus antigenic variantsHepatitis A is a liver inflammation caused by a virus. Its symptomatology is quite light and can disappear after the first weeks, but in some cases the disease can last for months. Among the most affected groups are men who have risky sexual behaviours with other men (MSM).This study analysed samples from MSM patients, both vaccinated and non-vaccinated, who caught the virus during an outbreak of Hepatitis A in Barcelona (2016-2018). The objective was to study the evolution of the virus and check whether there are emerging variants that can escape the effects of the vaccine. "We identified antigenic variants in vaccinated and non-vaccinated patients, but only the former increase in number, which suggests the positive selection", says Rosa Maria Pintó. "The use of mass sequencing to study this outbreak of hepatitis A has been key to identify these antigenic variants and their diversity", adds Dr. Josep Quer, head of Basic Research of Hepatitis C Virus of the Liver Disease Laboratory of the VHIR.The appearance of the Hepatitis A virus antigenic variants could become a threat to public health and could have consequences in the future uses of the current available vaccines. "If we select a variant which escapes the vaccine, this one would stop being effective. The study shows that, in cases such as the occurred one due the lack of vaccines, this can happen", notes the researcher.Reviewing vaccination practiceIn some countries, controlling recent outbreaks of Hepatitis A has been blocked by the low coverage of vaccination and lack of vaccines, which made administrations apply restrictions in the doses.During the outbreak, these restrictions affected especially people in the MSM group. "If a few doses of vaccination are given, or if the common doses were given long ago, or the vaccine is given to patients who caught the virus weeks ago, those variants of the virus that avoid the effects of the vaccine can be selected. This is especially relevant in the MSM group, since the virus dose through risky sexual practises is very high, and circulating antibodies are not enough to neutralize the inoculum or the first produced viruses", says Rosa Maria Pintó.In this sense, researchers recommend giving two doses of the vaccine and, in some situations stated in the publication, they suggest giving additional booster doses.Apart from specifying the vaccination protocol, the expert states they should "work in order to have easier-to-get vaccines so there are no vaccine shortages and doses do not have to be reduced".