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

Battogtokh Chimeddorj; Undram Mandakh; Linh-Vi Le; Batzorig Bayartsogt; Zolzaya Deleg; Oyunsuren Enebish; Oyunbaatar Altanbayar; Battur Magvan; Anuujin Gantumur; Otgonjargal Byambaa; Gerelmaa Enebish; Bat-Erdene Saindoo; Mandakhnaran Davaadorj; Avarzed Amgalanbaatar; Khangai Enkhtugs; Usukhbayar Munkhbayar; Batkhuu Bayanjargal; Tuyajargal Badamsambuu; Myagmartseren Dashtseren; Zolmunkh Narmandakh; Khongorzul Togoo; Enkh-Amar Boldbaatar; Ariunzaya Bat-Erdene; Yerkyebulan Mukhtar; Oyu-Erdene Shagdarsuren; Mandukhai Ganbat; Ochbadrakh Batjargal; Bayasgalantai Bavuusuren; Batzaya Batchuluun; Gereltsetseg Zulmunkh; Ganbaatar Byambatsogt; Khurelbaatar Nyamdavaa; Tserendagva Dalkh; Damdindorj Boldbaatar; Tuvshinjargal Tseren; Darambazar Gantulga; Otgonbayar Damdinbazar; Byambasuren Vanchin; Lorenzo Subissi; Isabel Bergeri; Davaalkham Dambadarjaa; Nymadawa Pagbajabyn; Gregory Greif; Ryenchindorj Erkhembayar

doi:10.1016/j.lanwpc.2021.100317

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

Lancet Reg Health West Pac. 2021 Dec:17:100317. doi: 10.1016/j.lanwpc.2021.100317. Epub 2021 Nov 23.

Authors

Battogtokh Chimeddorj^{1

2

3}, Undram Mandakh⁴, Linh-Vi Le⁵, Batzorig Bayartsogt⁶, Zolzaya Deleg¹, Oyunsuren Enebish⁷, Oyunbaatar Altanbayar¹, Battur Magvan¹, Anuujin Gantumur¹, Otgonjargal Byambaa¹, Gerelmaa Enebish¹, Bat-Erdene Saindoo¹, Mandakhnaran Davaadorj¹, Avarzed Amgalanbaatar⁸, Khangai Enkhtugs⁴, Usukhbayar Munkhbayar⁴, Batkhuu Bayanjargal⁴, Tuyajargal Badamsambuu⁴, Myagmartseren Dashtseren⁴, Zolmunkh Narmandakh⁹, Khongorzul Togoo⁹, Enkh-Amar Boldbaatar⁹, Ariunzaya Bat-Erdene⁹, Yerkyebulan Mukhtar⁶, Oyu-Erdene Shagdarsuren⁶, Mandukhai Ganbat⁶, Ochbadrakh Batjargal¹, Bayasgalantai Bavuusuren³, Batzaya Batchuluun³, Gereltsetseg Zulmunkh³, Ganbaatar Byambatsogt¹⁰, Khurelbaatar Nyamdavaa¹¹, Tserendagva Dalkh¹¹, Damdindorj Boldbaatar¹¹, Tuvshinjargal Tseren¹¹, Darambazar Gantulga¹¹, Otgonbayar Damdinbazar¹¹, Byambasuren Vanchin¹², Lorenzo Subissi¹³, Isabel Bergeri¹³, Davaalkham Dambadarjaa¹¹, Nymadawa Pagbajabyn¹⁴, Gregory Greif⁸, Ryenchindorj Erkhembayar^{2

8}

Affiliations

¹ Department of Microbiology and Infection Prevention Control, School of Biomedicine, Mongolian National University of Medical Sciences, Ulaanbaatar, Mongolia.
² Institute of Biomedical Sciences, Mongolian National University of Medical Sciences, Ulaanbaatar, Mongolia.
³ Mongolia Japan Hospital, Mongolian National University of Medical Sciences, Ulaanbaatar, Mongolia.
⁴ Department of Family Medicine, School of Medicine, Mongolian National University of Medical Sciences, Ulaanbaatar, Mongolia.
⁵ World Health Organization, Regional Office for the Western Pacific, Manila, Philippines.
⁶ Department of Epidemiology and Biostatistics, School of Public Health, Mongolian National University of Medical Sciences, Ulaanbaatar, Mongolia.
⁷ Department of Planning and Research, Ministry of Health, Ulaanbaatar, Mongolia.
⁸ Department of International Cyber Education, Graduate School, Mongolian National University of Medical Sciences, Ulaanbaatar, Mongolia.
⁹ Department of Immunology, School of Biomedicine, Mongolian National University of Medical Sciences, Ulaanbaatar, Mongolia.
¹⁰ Department of Biochemistry, School of Biomedicine, Mongolian National University of Medical Sciences, Ulaanbaatar, Mongolia.
¹¹ Mongolian National University of Medical Sciences, Ulaanbaatar, Mongolia.
¹² Department of Cardiology, School of Medicine, Mongolian National University of Medical Sciences, Ulaanbaatar, Mongolia.
¹³ World Health Organization, Geneva, Switzerland.
¹⁴ Mongolian Academy of Sciences, Ulaanbaatar, Mongolia.

Abstract

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.

Keywords: COVID-19; Immunity; Mongolia; Pandemics; SARS-CoV-2; Seroepidemiological studies; Seroprevalence.

Grants and funding

001/WHO_/World Health Organization/International