Epidemiological features and immunization against typhoid fever

Abstract

According to the World Health Organization, typhoid fever remains a serious problem for health services in many countries. From 11 to 21 million cases of typhoid fever are registered annually in the world, of which 128 000 to 161 000 are fatal. Typhoid fever is widespread in many countries in Africa, Asia, Central and South America. Due to the rapid development of global economic relations, transport communications and tourism in the XXI century, the threat of typhoid infection import will remain actual in many countries, including for Russia. The recent emergence of antibiotic-resistant strains of the pathogen complicates the treatment of the disease. Natural disasters also threaten epidemic outbreaks of typhoid fever. Based these facts, it is necessary to introduce permanently preventive typhoid vaccination as according to epidemic indications as among professional risk groups, labor migrants and tourists traveling to endemic regions. Russian typhoid Vi-polysaccharide liquid vaccine VIANVAC, which is a solution of chromatographically pure capsular polysaccharide – Vi-antigen, isolated from the supernatant of S. typhi culture, is registered and successfully used in the Russian Federation. The incidence of typhoid fever in Russia over the 20-year period of the VIANVAC application has decreased approximately 24 times – from 475 cases per year on average for 5-year period prior to vaccination in 1998 to 24 cases in 2017. 303,063 people at risk, as well as in areas of natural disasters associated with flooding of a number of territories, were vaccinated with VIANVAC vaccine in Russia in 2009–2018. In particular, 5950 and 8651 people were vaccinated during the flooding in Krymsk city in the Krasnodar region in 2012 and during the high water situation in the Khabarovsk region in 2013, respectively. According to the Rospotrebnadzor data, there were no cases of typhoid fever among vaccinated people. Conclusion. The high safety level of the VIANVAC allows the epidemiologist to make a rational decision on mass vaccination without fear of serious post-vaccination reactions among vaccinated people. Post-licensed studies of the VIANVAC indicate the possibility of conducting safe mass vaccinations in children's groups. A single injection scheme, a rapid (2–3 weeks) launch of an adaptive immune response justifies the use of the VIANVAC vaccine to eliminate outbreaks of disease and foci of infection.