# Seroprevalence of Immunoglobulin M and G antibodies to severe acute respiratory syndrome coronavirus 2 infection in Iwo, Nigeria

## TL;DR

This study found a high rate of past or recent SARS-CoV-2 infections in Iwo, Nigeria, based on antibody levels in blood samples from 360 people.

## Contribution

The study provides new seroprevalence data for SARS-CoV-2 in Nigeria, including insights into vaccinated individuals showing IgM antibodies.

## Key findings

- 51.1% of participants had SARS-CoV-2 antibodies, indicating prior infection.
- IgM antibodies were detected in 10.3% of participants, suggesting recent infections.
- Vaccinated individuals showed IgM antibodies in 11.8% of cases, indicating possible recent exposure.

## Abstract

In many countries, the preliminary stage of the COVID-19 pandemic has reached its climax and serological studies are extremely important in managing public health responses to the COVID-19 pandemic caused by SARS-CoV-2. The Nucleocapsid protein, a highly immunogenic protein, found only in infected individuals is important in SARS-CoV-2 infection. This study was therefore designed to determine the seroprevalence of SARS-CoV-2 IgM and IgG antibodies to nucleocapsid proteins in Iwo, Nigeria, thereby providing information on the spread of the infection.

Five millilitres of blood were collected from 360 individuals visiting four selected hospitals in Iwo, Nigeria. Socio-demographic and clinical data of the participants were obtained through a structured questionnaire. SARS-CoV-2 IgM and IgG antibodies against the nucleocapsid protein were detected from plasma samples using commercially available Enzyme-linked Immunoassay kits (Monobind Inc, USA) according to the manufacturer’s instructions. Statistical analyses were performed using SPSS software version 21 at P < 0.05 for statistical significance.

Out of the tested samples, 37 and 165 were positive for IgM and IgG antibodies giving a prevalence of 10.3% [95% CI: 7.5% − 13.6%] and 45.8% [95% CI: 40.8% − 50.8%], respectively. In total, 184 samples tested positive for SARS-CoV-2 antibodies giving an overall prevalence of 51.1% [95% CI: 45.8% − 56.1%]. Infection was associated with age; older population (35–90 years), fever, cough and muscle pain (p < 0.05). SARS-CoV-2 IgM and IgG antibodies were detected among 11.8% and 42.6% of COVID-19 vaccine recipients, respectively.

High seroprevalence of SARS-CoV-2 antibodies to nucleocapsid proteins were detected among the study population. In particular, is detecting IgM antibodies among those who have received COVID-19 vaccines. This reveals a high level of recent and past exposure to SARS-CoV-2 virus infection and continuous spread within the community.