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. 2022 Apr 27;17(4):e0263316.
doi: 10.1371/journal.pone.0263316. eCollection 2022.

Seroprevalence of anti-SARS-CoV-2 antibodies in Thai adults during the first three epidemic waves

Hatairat Lerdsamran  1 , Anek Mungaomklang  2 , Sopon Iamsirithaworn  3 , Jarunee Prasertsopon  1 , Witthawat Wiriyarat  4 , Suthee Saritsiri  5 , Ratikorn Anusorntanawat  6 , Nirada Siriyakorn  7 , Poj Intalapaporn  7 , Somrak Sirikhetkon  2 , Kantima Sangsiriwut  8 , Worawat Dangsakul  9 , Suteema Sawadpongpan  1 , Nattakan Thinpan  1 , Kuntida Kitidee  1 , Pilailuk Okada  9 , Ranida Techasuwanna  3 , Noparat Mongkalangoon  3 , Kriengkrai Prasert  10 , Pilaipan Puthavathana  1
Affiliations

Seroprevalence of anti-SARS-CoV-2 antibodies in Thai adults during the first three epidemic waves

Hatairat Lerdsamran et al. PLoS One. .

Abstract

This study determined the presence of anti-SARS-CoV-2 antibodies in 4964 individuals, comprising 300 coronavirus disease-19 (COVID-19) prepandemic serum samples, 142 COVID-19 patients, 2113 individuals at risk due to their occupations, 1856 individuals at risk due to sharing workplaces or communities with COVID-19 patients, and 553 Thai citizens returning after spending extended periods of time in countries with a high disease prevalence. We recruited participants between May 2020 and May 2021, which spanned the first two epidemic waves and part of the third wave of the COVID-19 outbreaks in Thailand. Their sera were tested in a microneutralization and a chemiluminescence immunoassay for IgG against the N protein. Furthermore, we performed an immunofluorescence assay to resolve discordant results between the two assays. None of the prepandemic sera contained anti-SARS-CoV-2 antibodies, while antibodies developed in 88% (15 of 17) of the COVID-19 patients at 8-14 days and in 94-100% of the patients between 15 and 60 days after disease onset. Neutralizing antibodies persisted for at least 8 months, longer than IgG antibodies. Of the 2113 individuals at risk due to their occupation, none of the health providers, airport officers, or public transport drivers were seropositive, while antibodies were present in 0.44% of entertainment workers. Among the 1856 individuals at risk due to sharing workplaces or communities with COVID-19 patients, seropositivity was present in 1.9, 1.5, and 7.5% of the Bangkok residents during the three epidemic waves, respectively, and in 1.3% of the Chiang Mai people during the first epidemic wave. The antibody prevalence varied between 6.5 and 47.0% in 553 Thai people returning from high-risk countries. This serosurveillance study found a low infection rate of SARS-CoV-2 in Thailand before the emergence of the Delta variant in late May 2021. The findings support the Ministry of Public Health's data, which are based on numbers of patients and contact tracing.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. SARS-CoV-2 infections in Thailand from 1 March 2020, through 21 December 2021.
Fig 2
Fig 2. Antibody responses in COVID-19 patients at different time points after the onset of disease symptoms.
Fig 3
Fig 3. Correlation between NT antibody titers and Architect IgG indices in COVID-19 patients.
Fig 4
Fig 4. Correlation between NT antibody titers and Architect IgG indices in Thai people.
See this image and copyright information in PMC

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