RBD-specific antibody response after two doses of different SARS-CoV-2 vaccines during the mass vaccination campaign in Mongolia.

The SARS-CoV-2 vaccination campaign began in February 2021 and achieved a high rate of 62.7% of the total population fully vaccinated by August 16, 2021, in Mongolia. We aimed to assess the initial protective antibody production after two doses of a variety of types of SARS-CoV-2 vaccines in the Mongolian pre-vaccine antibody-naïve adult population. This prospective study was conducted from March-April to July-August of 2021. All participants received one of the four government-proposed COVID-19 vaccines including Pfizer/BioNTech (BNT162b2), AstraZeneca (ChAdOx1-S), Sinopharm (BBIBP-CorV), and Sputnik V (Gam-COVID-Vac). Before receiving the first shot, anti-SARS-CoV-2 S-RBD human IgG titers were measured in all participants (n = 1833), and titers were measured 21-28 days after the second shot in a subset of participants (n = 831). We found an overall average protective antibody response of 84.8% (705 of 831 vaccinated) in 21-28 days after two doses of the four types of COVID-19 vaccines. Seropositivity and titer of protective antibodies produced after two shots of vaccine were associated with the vaccine types, age, and residence of vaccinees. Seropositivity rate varied significantly between vaccine types, 80.0% (28 of 35) for AstraZeneca ChAdOx1-S; 97.0% (193 of 199) for Pfizer BNT162b2; 80.7% (474 of 587) for Sinopharm BBIBP-CorV, and 100.0% (10 of 10) for Sputnik V Gam-COVID-Vac, respectively. Immunocompromised vaccinees with increased risk for developing severe COVID-19 disease had received the Pfizer vaccine and demonstrated a high rate of seropositivity. A high geometric mean titer (GMT) was found in vaccinees who received BNT162b2, while vaccinees who received ChAdOx1-S, Sputnik V, and BBIBP-CorV showed a lower GMT. In summary, we observed first stages of the immunization campaign against COVID-19 in Mongolia have been completed successfully, with a high immunogenicity level achieved among the population with an increased risk for developing severe illness.

Hepatitis B, C, and D Virus Infection among Population Aged 10-64 Years in Mongolia: Baseline Survey Data of a Nationwide Cancer Cohort Study.

Hepatitis B, C, and D virus infections are a major public health problem, and Mongolia has one of the highest prevalences of dual and triple infections in the world. We aimed to determine the seroprevalence of hepatitis infection and dual or triple hepatitis infections among 10-64-year-olds. A questionnaire was used to identify risk factors for hepatitis infection, and seromarkers were measured by the fully automated immunologic analyzer HISCL-5000. Among a total of 10,040 participants, 8.1% of the population aged 10-64 was infected with HBV, 9.4% with HCV, and 0.4% with HBV and HCV, and the prevalence of the disease varied by age, sex, and the area of residence. Young people were particularly unaware of their hepatitis infection status. A small proportion of children aged 10 to 19 years and the majority of adults younger than 30 years were unaware of their HBV and HCV infection. Men were also more likely to be unaware of their HBV and HCV infection status than women. The results suggested that the prevalence of infection in the general population is high and that most people are unaware that they are infected or have become chronic carriers. Identifying mono-, co-, or triple-infection status is critical to prevent the rapid progression of liver disease among the Mongolian population.

Hepatitis B, C, and D Virus Infections and AFP Tumor Marker Prevalence Among the Elderly Population in Mongolia: A Nationwide Survey.

OBJECTIVES: Infections with hepatitis B, C, and D virus (HBV, HCV, and HDV) are a major public health problem and lead to serious complications such as cirrhosis and hepatocellular carcinoma. We aimed to determine the seroprevalence of hepatitis B surface antigen (HBsAg), anti-HCV, anti-HDV immunoglobulin G, alpha-fetoprotein (AFP), and dual and triple hepatitis virus infections in Mongolia. METHODS: A total of 2313 participants from urban and rural regions were randomly recruited for this cross-sectional study. A questionnaire was used to identify the risk factors for hepatitis virus infections, and the seromarkers were measured using immunoassay kits. RESULTS: Among all participants, the prevalence of HBV, HCV, and HDV was 15.6%, 36.6%, and 14.3%, respectively. The infection rates were significantly higher in females and participants with a lower education level, rural residence, older age, and a history of blood transfusion. HBV and HCV co-infection was found in 120 (5.2%) participants and HBV, HCV, and HDV triple infection was detected in 67 (2.9%) participants. The prevalence of elevated AFP was 2.7%, 5.5%, and 2.6% higher in participants who were seropositive for HBsAg (p=0.01), anti-HCV (p<0.001), and anti-HDV (p=0.022), respectively. Elevated AFP was more prevalent in participants co-infected with HBV and HCV (5.8%, p=0.023), HBV and HDV (6.0%, p<0.001), and triple-infected with HBV, HCV, and HDV (7.5%) than in uninfected individuals. CONCLUSIONS: Nearly half (49.8%) of the study population aged ≥40 years were infected with HBV, HCV, or HDV, and 22.4% had dual or triple infections.

SARS-CoV-2 seroprevalence in Mongolia: Results from a national population survey.

BACKGROUND: With the global spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in early 2020, Mongolia implemented rapid emergency measures and did not report local transmission until November 2020. We conducted a national seroprevalence survey to monitor the burden of SARS-CoV-2 in Mongolia in the months surrounding the first local transmission. METHODS: During October-December 2020, participants were randomly selected using age stratification and invited for interviews and blood samples at local primary health centres. We screened for total SARS-CoV-2 antibodies, followed by two-step quantitative SARS-CoV-2 IgG serology tests for positive samples. Weighted and test-adjusted seroprevalences were estimated. We used chi-square, Fisher's exact and other tests to identify variables associated with seropositivity. FINDINGS: A total of 5000 subjects were enrolled. We detected SARS-CoV-2 IgG antibodies in 72 samples. Crude seroprevalence of SARS-CoV-2 antibodies was 1·44% (95%CI,1·21-1·67). Population weighted and test-adjusted seroprevalences were 1·36% (95%CI,1·11-1·63) and 1·45% (95%CI,1·11-1·63), respectively. Age, sex, geographical, and occupational factors were not associated with seropositivity (p>0·05). Symptoms and signs within past 3 months and seropositivity were not associated at the time of the survey (p>0·05). INTERPRETATION: SARS-CoV-2 seroprevalence in Mongolia was low in the first year of the pandemic potentially due to strong public health measures, including border restrictions, educational facilities closure, earlier adoption of mask-wearing and others. Our findings suggest large-scale community transmission could not have occurred up to November 2020 in Mongolia. Additional serosurveys are needed to monitor the local pandemic dynamic and estimate how far from herd immunity Mongolia will be following-up with vaccination programme in 2021 and 2022. FUNDING: World Health Organisation, WHO UNITY Studies initiative, with funding by the COVID-19 Solidarity Response Fund and the German Federal Ministry of Health (BMG) COVID-19 Research and development. TRANSLATION: Cyrillic and Traditional Mongolian translation of abstract is available on appendix section.