Virologists measure the level of herd immunity to hepatitis A virus

RUDN University virologists measured the level of herd immunity to hepatitis A virus in different regions of Russia. The results make it possible to assess the effectiveness of the vaccination program. The study showed that mass vaccination should be introduced in all regions. The results are published in Vaccines.

Seroprevalence data are needed to make decisions about mass vaccination. This term in virology refers to the proportion of people who test positive for a disease or antibodies to its causative agent in a blood serum test. This value is also associated with herd immunity. There are practically no such data for hepatitis A virus (HAV) in Russia, although childhood vaccination programs have been introduced in some regions. RUDN University virologists and colleagues collected data from different regions of the country and analyzed seroprevalence and vaccination programs.

Despite the decrease in the number of infections in recent years, the incidence of hepatitis A in Russia still retains the general patterns inherent in previous years. Since 2001, HAV vaccination has been included in the Russian national vaccination schedule only for occupational risk groups. However, over the past decade, a number of regional hepatitis A vaccination programs have been adopted in Russia. But a comprehensive analysis of vaccination coverage under these programs has not yet been carried out."

Karen Kyuregyan, Researcher at the Scientific and Educational Resource Center for High-Performance Methods of Genomic Analysis, RUDN University

The study included data for 2008 and 2020-2021 on 5 regions remote from each other and covering the entire distance from west to east of Russia (Moscow region, Sverdlovsk region, Tuva Republic, Sakha Republic, Khabarovsk region). All of them differ in climatic, economic, social and demographic parameters. In addition, each of them has its own strategy for vaccination against hepatitis A. RUDN University doctors examined the blood serum of healthy volunteers. None of them showed signs of infectious diseases. In total, there were 2,000 to 8,000 volunteers in each region.

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In regions where mass vaccination was not introduced, the seroprevalence rate did not exceed the national average. In Moscow, herd immunity has aged. In 2008, the 50% seroprevalence barrier was overcome in people over 40, and in 2020 – over 59. A similar situation is in the Khabarovsk Territory in the east of the country. There, the protective level of 50% immunity has shifted by 10 years, from 30 to 40. In Yakutia and Tuva, a vaccination program was introduced in 2011-2012. Its results are visible in the study. So, in Yakutia, by 2020, 50% seroprevalence among people under 20 was achieved. In 2008, this figure was at the level of 20-30%. RUDN doctors concluded that vaccination should be introduced throughout the country.

"These data suggest that general hepatitis A vaccination should be implemented at the national level. To maintain the effectiveness of existing vaccination programs, it is recommended to control the coverage and carry out catch-up vaccination," Karen Kyureghyan, Researcher at the Scientific and Educational Resource Center for High-Performance Methods of Genomic Analysis, RUDN University.