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    Item type:Publication,
    One-year antibody kinetics and effectiveness of a BNT162b2 booster after four primary COVID-19 vaccination regimens in Mongolia
    (2026-09)
    Bazarjav, Purevbat
    ;
    Erdene-Ochir, Tseyenkhorloo
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    Sandagdorj, Ankhbayar
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    Enkhtuvshin, Altansukh
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    Enkhbayar, Purevjargal
    BACKGROUND: Waning immunity after primary COVID-19 vaccination and the widespread use of heterogeneous vaccine platforms have created uncertainty regarding the durability of protection following booster vaccination. Mongolia implemented a mixed-platform vaccination program and deployed BNT162b2 as a booster. We evaluated the immunogenicity, effectiveness, and safety of a BNT162b2 booster following four primary vaccination regimens with 12 months follow-up. METHODS: In this prospective observational study in Ulaanbaatar, Mongolia, adults (≥18 years) who had completed a homologous two-dose primary series with BBIBP-CorV, ChAdOx1 nCoV-19, Gam-COVID-Vac, or BNT162b2 received a BNT162b2 booster a median of 189 days (IQR 186-215) after the second dose and were grouped according to their primary vaccination regimen. Humoral immune responses (anti-SARS-CoV-2 N/S1-RBD IgG, S-RBD IgG, and neutralizing antibodies) were measured at baseline and at multiple time points up to 12 months after booster vaccination. Reactogenicity was monitored for 28 days. SARS-CoV-2 infection was ascertained by a positive antigen/lateral-flow test and/or RT-PCR. VE was estimated for prespecified follow-up intervals by comparing the risk of SARS-CoV-2 infection in each boosted group with that in an unvaccinated comparison group. FINDINGS: Among 311 participants (mean age 41.88 years [SD 13.64]; 175 [56.27%] women and 136 [43.73%] men), antibody responses peaked at day 14 and declined through day 365 in all groups. At day 14, total antibody concentrations were highest in BNT + BNT (385.03 U/mL) and lowest in Gam + BNT (341.74 U/mL). S-RBD IgG at day 14 was highest in BNT + BNT (967.0 ng/mL) and lowest in BBIBP+BNT (863.70 ng/mL). Neutralizing antibodies at day 14 were highest in BNT + BNT (368.13 AU/mL) and BBIBP+BNT (336.70 AU/mL). During follow-up, 64 participants acquired SARS-CoV-2 infection and 15 (23.44%) were admitted to hospital. Reactogenicity was predominantly mild-to-moderate, and laboratory parameters were generally within acceptable ranges. Vaccine effectiveness declined from 1 month to 12 months: BBIBP+BNT 90.54% (95% CI 59.71-97.78) to 71.17% (39.66-86.23); ChAd+BNT 84.97% (49.75-95.51) to 52.59% (8.61-75.41); Gam + BNT 89.68% (23.95-98.60) to 63.84% (15.10-84.60); BNT + BNT 91.89% (40.06-98.90) to 72.29% (34.37-88.30). INTERPRETATION: A BNT162b2 booster following diverse primary COVID-19 vaccination regimens induced strong humoral responses that declined over 12 months and showed an acceptable reactogenicity profile. VE against SARS-CoV-2 infection was highest soon after boosting and lower later in follow-up. Although antibody levels and VE showed similar temporal patterns, these findings should be interpreted as complementary outcomes rather than evidence of a direct causal relationship or a formal immunological correlate of protection.
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    Item type:Publication,
    The Dynamics of the Prevalence of Acute Viral Hepatitis and the Strategies against Viral Hepatitis in Mongolia
    (2024) ;
    Badamjav, Tegshjargal
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    Dondov, Ganchimeg
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    Dashjamts, Gantogtokh
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    BACKGROUND: Hepatocellular carcinoma (HCC) is the most common cancer in Mongolia. The relative importance of hepatitis B virus (HBV) and hepatitis C virus (HCV) infections in HCC etiology is known to vary greatly from one part of the world to another. Principally, 95% of HCC patients have chronic viral hepatitis, including 53% hepatitis B virus, 38.9% HCV, and 5.6% have HBV/HCV coinfection. Hepatitis D virus (HDV) infection is widely spread in our country, anti-HDV has been found in more than 25% of carriers who have HBsAg. MATERIALS AND METHODS: We analyzed data of patients who had been diagnosed with acute viral hepatitis in the Department of adult hepatitis, National Center for Communicable Diseases in Mongolia from 1952 to 2018. RESULTS: A total of 318,831 cases of acute viral hepatitis were registered in Mongolia between 1981 and 2019, which is 34.9 cases per 10,000 population. Of these, 265,931 cases of acute viral hepatitis A, or 28.6 per 10,000 populations, 48,855 cases of acute viral hepatitis B, or 5.5 cases per 10,000 populations, and 2,607 cases of acute viral hepatitis C, or 0.4 cases per 10,000 populations were recorded. CONCLUSION: The prevalence of viral hepatitis in our country was the highest in 1981-1991, but since 2012, the prevalence of infection has steadily decreased. In Mongolia, since 1960, multifaceted programs and activities to combat viral hepatitis have been successfully implemented at the national level. HOW TO CITE THIS ARTICLE: Badamnachin B, Badamjav T, Dondov G, et al. The Dynamics of the Prevalence of Acute Viral Hepatitis and the Strategies against Viral Hepatitis in Mongolia. Euroasian J Hepato-Gastroenterol 2024;14(1):65-69.