Sereejav, Enkhbold

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Antibody Responses to mRNA Versus Non-mRNA COVID Vaccines Among Mongolian Population
(Elsevier BV, 2022)
Sereejav, Enkhbold
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Sandagdorj, Ankhbayar
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Bazarjav, Purevbat
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Ganbold, Sarangua
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Enkhtuvshin, Altansukh
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Antibody responses to mRNA versus non-mRNA COVID vaccines among the Mongolian population
(Elsevier BV, 2023-09)
Sereejav, Enkhbold
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Sandagdorj, Ankhbayar
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Bazarjav, Purevbat
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Ganbold, Sarangua
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Enkhtuvshin, Altansukh
Scopus© Citations 4
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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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Molecular epidemiology of SARS-CoV-2 in Mongolia, first experience with nanopore sequencing in lower- and middle-income countries setting
(Wiley, 2023-12)
Erendereg, Munkhtuya
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Tumurbaatar, Suvd
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Byambaa, Otgonjargal
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Enebish, Gerelmaa
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Burged, Natsagdorj
BACKGROUND: Coronavirus disease (COVID-19) has had a significant impact globally, and extensive genomic research has been conducted on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) lineage patterns and its variants. Mongolia's effective response resulted in low prevalence until vaccinations became available. However, due to the lack of systematically collected data and absence of whole genome sequencing capabilities, we conducted a two-stepped, nationally representative molecular epidemiologic study of SARS-CoV-2 in Mongolia for 2020 and 2021. METHODS: We used retrospective analysis of stored biological samples from November 2020 to October 2021 and a variant-specific real-time reverse transcription polymerase chain reaction (RT-PCR) test to detect SARS-CoV-2 variants, followed by whole genome sequencing by Nanopore technology. Samples were retrieved from different sites and stored at -70°C deep freezer, and tests were performed on samples with cycle threshold <30. RESULTS: Out of 4879 nucleic acid tests, 799 whole genome sequencing had been carried out. Among the stored samples of earlier local transmission, we found the 20B (B.1.1.46) variant predominated in the earlier local transmission period. A slower introduction and circulation of alpha and delta variants were observed compared to global dynamics in 2020 and 2021. Beta or Gamma variants were not detected between November 2020 and September 2021 in Mongolia. CONCLUSIONS: SARS-CoV-2 variants of concerns including alpha and delta were delayed in circulation potentially due to public health stringencies in Mongolia. We are sharing our initial experience with whole genome sequencing of SARS-CoV-2 from Mongolia, where sequencing data is sparse.
Scopus© Citations 1

Sereejav, Enkhbold

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