Changes in seroprevalence and acute infection rates after vaccination and herd immunity in a pediatric hospital in the Southeastern Anatolia region of Turkey: Effects of adding hepatitis a vaccine to the Extended National Immunization Program

Aim: This study was designed to compare rates of acute HAV infection and HAV seroprevalence in patients aged 0-6 years and 7-15years in a pediatric hospital before and after the HAV vaccine was added to the national immunization program in 2012.Material and Methods: A total of 16,917 serum samples were evaluated in the study. Sera of the 5520 patients (3,208 of 0-6 years,2,312 of 7-15 years) were collected during 2011 and analyzed for anti-HAV IgM and anti-HAV IgG with chemiluminescent assay(period 1). After that a total of 11,397 sera of the patients (5,473 of 0-6 years and 5,924 of 7-15 years) were collected between 1 July2014 and 31 December 2016 and analyzed for anti-HAV IgM and anti-HAV total (period 2).Results: In period 1, rates of acute HAV infection and seropositivity were 26.87% and 19.25% in the 0-6 years , and 42.39% and 41.52%in the 7-15 years. Prior to routine vaccination, 54.03% of patients in the 0-6 age group and 16.08% of patients in the 7-15 age groupswere susceptible to HAV infection.In period 2, Anti-HAV IgM positivity rates in 2014, 2015, and 2016 were 14.06%, 3.92%, and 2.46%in the 0-6 age group and 16.85%, 6.80%, and 4.48% in the 7-15 age group, respectively. Seropositivity rates were 43.66%, 59.55%, and66.09% in the 0-6 age group and 45.67%, 55.41%, and 54.04% in the 7-15 age group, respectively. After routine vaccination, rates ofchildren who were susceptible to HAV infection decreased from 42.28% and 36.52 % to 31.45% in the 0-6 years and increased from37.48%, 37.79% to 41.48% in the 7-15 years. Considering the data as a whole, the most striking finding was that the acute infectionrate in the 0-6 years was decreased firstly by 47.67% and then by 85.42% and 90.85% compared to the pre-vaccination period.However, a progressive decline was also observed in the 7-15 years compared to the pre-vaccination period; the rate decreased by60.25%, 83.96%, and 89.43%, respectively in period 2. This fall in infection rates among a non-target group of HAV vaccination canbe attributed to the effect of the vaccine on "herd immunity".Conclusion: Adding HAV vaccine to the routine immunization program effectively reduced rates of acute infection, demonstrating thecontribution of vaccination to herd immunity. Studies showing the efficacy of vaccination programs are essential for raising publicawareness.

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1. WHO position paper on hepatitis A vaccines-June 2012. Wkly Epidemiol Rec 2012;87:261-76.
2. Mıstık R. The epidemiology of viral hepatitis in TurkeyEvaluation of publications. In: Tabak F, Balık İ, Tekeli E (editors). Viral Hepatitis (1st ed). Ankara: Viral Hepatitis Society 2007:10-50.
3. Mıstık R, Balık İ. Epidemiological analysis of viral hepatitis in Turkey. In: Balık İ, Tekeli E (editors). Viral Hepatitis (1st ed). Ankara: Viral Hepatitis Society 2002:3-35.
4. Hayajneh WA, Daniels VJ, James CK, Kanıbir MN, Pilsbury M, Marks M et al. Public health impact and cost effectiveness of routine childhood vaccination for hepatitis a in Jordan: a dynamic model approach. BMC Infect Dis 2018;18:119.
5. Anderson DA. Hepatitis A and E viruses. In: Murray PR, Baron EJ, Jorgensen JH, Landry ML, Pfaller MA (editors). Clinical Microbiology (9th ed). Washington: ASM Press 2009:1424-36.
6. Murray PR, Rosenthal KS, Pfaller MA. Hepatitis viruses. In: Murray PR, Rosenthal KS, Pfaller MA (editors). Medical Microbiology (6th ed). Philadelphia: Mosby Elsevier 2010:645-59.
7. Yiş R, Değirmenci S. Evaluation of Serologic Markers of Viral Hepatitis Due to a Hepatitis A Virus Outbreak Following an Acute Hepatitis A Infection in a Child in the Gaziantep Orphanages. Turkiye Klinikleri J Med Sci 2013;33:110-15.
8. Karaman S, Karaman K, Kızılyıldız BS, Ceylan N, Kaba S, Parlak M, et al. Seroprevalence of hepatitis a and associated factors among 1-15 year old children in Eastern Turkey. Int J Clin Exp Med 2015;8:19394-9.
9. Saberifiroozi M. Prevention of hepatitis A infection. Hepatitis Monthly 2005;5:19-27.
10. Cianciara J. Hepatitis A shifting epidemiology in Poland and Eastern Europe. Vaccine 2000;18:68-70.
11. Tufenkeji H. Hepatitis A shifting epidemiology in the Middle East and Africa. Vaccine 2000;18:65-67.
12. Kanra G, Tezcan S, Badur S. Hepatitis A seroprevalence in a random sample of the Turkish population by simultaneous EPI cluster and comparison with surveys in Turkey. Turk J Pediatr 2002;44: 204-210.
13. Altınkaynak S, Selimoğlu MA, Ertekin V, Kılıçaslan B. Epidemiological factors affecting hepatitis a seroprevalence in childhood in a developing country. Eurasian J Med 2008;40:25-8.
14. Özen M, Yoloğlu S, Işık Y, Yetkin G. AntiHBs seropositivity in children aged between 2-16 years who were admitted to Turgut Özal Medical Center. Turk Ped Ars 2006;41:36-40.
15. Ceyhan M, Yildirim I, Kurt N, Uysal G, Dikici B, Ecevit C, et al. Differences in Hepatitis A Seroprevalence Among Geographical Regions in Turkey: a need for regional vaccination recommendations. Viral Hepat J 2008;15:69-72.
16. Turhan E, Çetin M. The Seroprevalence of Viral Hepatitis A in Patients Who Had Consulted at Mustafa Kemal University of Medicine Faculty. Viral Hepat J 2007;12:30-4.
17. Türker T, Babayiğit MA, Tekbaş ÖF, Oğur R, Avcı IY, Pahsa A, et al. Frequency and distribution of hospitalizations due to viral hepatitis at Gulhane Military Medical Academy between 2002 and 2004. Gulhane Med J 2006;48:125-31.
18. Yamazhan T. Hepatitis A: Epidemiology, Transmission and Prevention. Turkiye Klinikleri J Gastroenterohepatol-Special Topics 2010;3:7-10.
19. Badur S. Hepatitis A, B and D viruses. Ustaçelebi Ş, Abacıoğlu H, Badur S (editors). Moleküler, klinik ve tanısal viroloji (1.Baskı). Ankara: Güneş Kitabevi, 2004:175-202.
20. Copur Cicek A, Ozkasap S, Dereci S, Şahin K, Ulusan Gündoğdu DZ, Dilek AR, et al. Seroprevelance of HAV, HBV, HCV in Pediatric Patients in Rize City. Viral Hepat J 2012;18:102-6.
21. Doğan E, Sevinç E, Kuru C. Seroprevalence of HAV, HBV, and HCV in pediatric patients in Karabük province. Turkish J Academic Gastroenterol 2017;16:97-100.
22. Mohd Hanafiah K, Jacobsen KH, Wiersma ST. Challenges to mapping the health risk of hepatitis A virus infection. Int J Health Geogr 2011;10: 57.
23. Jacobsen KH, Wiersma ST. Hepatitis A virus seroprevalence by age and world region, 1990 and 2005. Vaccine 2010;28:6653-7.
24. Vizzotti C, Gonzalez J, Gentile A, Rearte A, Ramonet M, Cañero-Velasco MC, et al. Impact of the Singledose Immunization Strategy Against Hepatitis A in Argentina. Pediatr Infect Dis J 2014;33:84-8.
25. Vaccine Information Statement Hepatitis A Vaccine Internet. Centers for Disease Control and Prevention; c2011. Available from: https://www.cdc.gov/ vaccines/hcp/vis/vis-statements/hep-a.pdf
26. WHO position paper on hepatitis A vaccines: June 2012-Recommendations. Vaccine 2013;31:285-6.
27. Nymark LS, Sharma T, Miller A, Enemark U, Griffiths UK. Inclusion of the value of herd immunity in economic evaluations of vaccines. A systematic review of methods used. Vaccine 2017;35:6828-41.
28. Yoldaş Ö, Bulut A, Altındiş M. The Current Approach of Hepatitis A Infections. Viral Hepat J 2012;18:81-6.