Бадамначин, Батсүх

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One-year antibody kinetics and effectiveness of a BNT162b2 booster after four primary COVID-19 vaccination regimens in Mongolia
(2026-09)
Bazarjav, Purevbat
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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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Risk factors associated with hepatitis D virus infection and preventive strategies in Mongolia
(Ovid Technologies (Wolters Kluwer Health), 2024-05)
Su, Chien-Wei
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Ochirkhuree, Bayarmaa
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Namdag, Bira
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Badamnachin, Batsukh
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Ganbold, Sarangua
BACKGROUND: Hepatitis D virus (HDV) infection is highly prevalent in Mongolia. We aimed to identify the risk factors associated with HDV infection, propose preventive strategies, and evaluate the outcomes of a 3-year collaborative project between Taiwan and Mongolia. METHODS: In 2016 and 2018, we conducted onsite visits to Mongolia. Mongolian investigators collected questionnaires focusing on risk factors, demographic characteristics, and serum samples for acute HDV infections. Furthermore, 19 Mongolian seed teachers participated in a 1-week workshop on infection control in Taiwan. Subsequently, these seed teachers trained more than 400 medical personnel in Mongolia. To assess secular changes in acute HDV infection, we reviewed the registration data from the National Center for Communicable Disease (NCCD) in Mongolia between 2011 and 2021. RESULTS: Among the 194 Mongolian patients, 108 had dual infection with hepatitis B virus (HBV) and HDV, while 86 had acute hepatitis B (AHB). Patients with HBV/HDV dual infections were older (28.6 vs 25.5 years, p = 0.030) and had lower rates of positive hepatitis B e antigen in their sera, lower rates of serum HBV DNA exceeding 2000 IU/mL, and higher rates of having received dental treatment (59.4% vs 40.5%, p = 0.014) and injection therapy (64.2% vs 44.0%, p = 0.009) compared with those with AHB. Analysis of NCCD data revealed that new HDV infection cases were more prevalent between 2011 and 2015 (111.20 ± 29.79 cases/y) and decreased to 54.67 ± 27.34 cases/y between 2016 and 2021 ( p = 0.010). CONCLUSION: Dental treatment and injections were associated with a higher risk of acute HDV infections in Mongolia. Through collaborative efforts, the incidence rate of HDV infection has declined in recent years.

Б.Батсүх

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