Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) immunoglobulin G (IgG) detection can be an effective complementary tool to the reverse transcription–polymerase chain reaction (RT-PCR) test in estimating the true burden of coronavirus diseases 2019 (COVID-19) and can serve as baseline data, especially after the roll-out of vaccines against SARS-CoV-2. In this study, we aim to determine the seropositivity of SARS-CoV-2 IgG among people in Dhaka, Bangladesh. Volunteers, mostly asymptomatic people from Dhaka, were enrolled between October 2020 and February 2021. After obtaining participants' signed consents, blood samples were tested for SARS-CoV-2 IgG antibody, following the standard protocol of testing within 72 hours of collection. SARS-CoV-2 IgG was positive in 42% (101/239) of the cases. No difference was observed in terms of IgG positivity and IgG levels when stratified by age, gender, and blood group. However, RT-PCR-positive cases presented higher IgG levels compared to RT-PCR-negative/RT-PCR-not performed cases. SARS-CoV-2 IgG was found in 31% (32/102) and 28% (19/67) of RT-PCR-negative and RT-PCR-not performed cases, respectively. For RT-PCR-positive but SARS-CoV-2 IgG-negative cases (n = 13), the average time gap between the RT-PCR and SARS-CoV-2 IgG tests of six months indicates a gradual reduction of IgG. Eight cases for which samples were tested at two time points, three months apart, showed presented a decline in IgG levels with time (median IgG index of 2.55 in the first sample versus 1.22 in the second sample). Our findings reveal that several mild/asymptomatic cases that were RT-PCR-negative/not tested exist in the community, and IgG levels reduce in the human body over time.
Highlights
Coronavirus disease 2019 (COVID-19), first reported on December 30, 2019, in Wuhan Province of China, spreads rapidly worldwide, leading the World Health Organization (WHO) to declare it a pandemic on March 11, 2020 [1]
The seropositivity of immunoglobulin G (IgG) antibodies among the samples tested for our study, 6 months after the first detected case in the country, was found to be 42%. This is much higher than the community seroprevalence reported in other parts of the world: 2.8% in California, USA [9], 7.6% in Daegu, Korea [10], 5% in Spain [11], a comparable 22–33% in Iran [12], and 25.41% in Niger State, Nigeria [13]. This proportion indicates that the true burden of COVID-19 in Bangladesh might be much greater than that estimated by the reverse transcription–polymerase chain reaction- (RTPCR-)based detection method
Our results indicated that the seropositivity of IgG among the participants tested was 42%, and the IgG positivity did not differ in terms of age, gender, and blood group
Summary
Coronavirus disease 2019 (COVID-19), first reported on December 30, 2019, in Wuhan Province of China, spreads rapidly worldwide, leading the World Health Organization (WHO) to declare it a pandemic on March 11, 2020 [1]. The first case of COVID-19 in Bangladesh was reported on March 8, 2020. Till April 26, 2021, 745,322 COVID-19 cases have been detected with 11,053 deaths. The overall prevalence of COVID-19 was 13.9%, with a case fatality rate of 1.48% [2]. Managing this pandemic entails halting the virus transmission or developing immunity among the masses against SARS-CoV-2 through vaccination programs. Various steps such as hand sanitization, wearing of face masks, and social distancing have been enforced throughout the country.
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