Seroprevalence and risk factors for SARS-CoV-2 infection among unvaccinated adults in a rural community in South-East Nigeria during the Omicron era: a community-based cross-sectional study
- 1Department of Internal Medicine, University of Port Harcourt Teaching Hospital, Port Harcourt, Rivers State Nigeria
- 2Department of Internal Medicine, Alex Ekwueme Federal University Teaching Hospital, Abakaliki, Ebonyi State Nigeria
- 3Department of Medicine, University of Nigeria Teaching Hospital, Ituku/Ozalla, Enugu State Nigeria
Abstract
Background: Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) infection is an emerging viral disease that became a global pandemic in March 2020. Despite the protracted pandemic, population-based local data on the burden and exposure risks of SARS-CoV-2 infection remain limited in most parts of sub-Saharan Africa, where the pandemic surprisingly defied early public health predictions.
Methods: A community-based cross-sectional study of 252 consenting unvaccinated adults was conducted from March 11 to June 12, 2022, in Enugu State, southeastern Nigeria. A two-stage cluster sampling design was used, with a validated, interviewer-administered questionnaire adapted from the World Health Organization Unity Study Protocol, to collect demographic, socio-behavioural, and clinical data. Each participant was tested for SARS-CoV-2 IgM and IgG antibodies by the enzyme-linked immunosorbent assay. Multivariate analysis was used to determine factors independently associated with SARS-CoV-2 seropositivity. A P-value of < 0.05 was considered statistically significant.
Results: The mean age was 47.72 ± 17.92 years, with 57.14% (144) female. The seroprevalence of SARS-CoV-2 (IgG or IgM) was 67.90%. Thirty-nine (15.48%) out of 252 participants had both SARS-CoV-2 IgG and IgM antibodies. Multivariable logistic regression analysis showed that healthcare workers had significantly higher odds of SARS-CoV-2 seropositivity than non-healthcare workers (adjusted odds ratio [aOR] = 3.83, 95% confidence interval [CI]: 1.52–9.66; P = 0.004).
Conclusion: Serological evidence of SARS-CoV-2 infection was observed in approximately two out of every three unvaccinated adults, indicating widespread previous exposure through natural infection in the study population by the first half of 2022. The predominance of SARS-CoV-2 IgG over IgM antibodies suggests that most infections occurred before sample collection and is consistent with declining community transmission during the study period. Healthcare worker status was independently associated with SARS-CoV-2 seropositivity, reinforcing the importance of strengthening infection prevention and control measures to protect frontline healthcare workers during future emerging infectious disease outbreaks.
Supplementary Information: The online version contains supplementary material available at https://doi.org/10.1186/s12879-026-14139-z.
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BibTeX
@article{onyeaghala2026seroprevalence,
title = {{Seroprevalence and risk factors for SARS-CoV-2 infection among unvaccinated adults in a rural community in South-East Nigeria during the Omicron era: a community-based cross-sectional study}},
author = {Chizaram Onyeaghala and Uche Unigwe and Nneka Chika-Igwenyi and Michael Iroezindu},
journal = {BMC Infectious Diseases},
year = {2026},
month = jul,
doi = {10.1186/s12879-026-14139-z},
url = {https://doi.org/10.1186/s12879-026-14139-z},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - JOUR
TI - Seroprevalence and risk factors for SARS-CoV-2 infection among unvaccinated adults in a rural community in South-East Nigeria during the Omicron era: a community-based cross-sectional study
AU - Chizaram Onyeaghala
AU - Uche Unigwe
AU - Nneka Chika-Igwenyi
AU - Michael Iroezindu
PY - 2026
DA - 2026/07/31
JO - BMC Infectious Diseases
DO - 10.1186/s12879-026-14139-z
UR - https://doi.org/10.1186/s12879-026-14139-z
AB - Background: Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) infection is an emerging viral disease that became a global pandemic in March 2020. Despite the protracted pandemic, population-based local data on the burden and exposure risks of SARS-CoV-2 infection remain limited in most parts of sub-Saharan Africa, where the pandemic surprisingly defied early public health predictions. Methods: A community-based cross-sectional study of 252 consenting unvaccinated adults was conducted from March 11 to June 12, 2022, in Enugu State, southeastern Nigeria. A two-stage cluster sampling design was used, with a validated, interviewer-administered questionnaire adapted from the World Health Organization Unity Study Protocol, to collect demographic, socio-behavioural, and clinical data. Each participant was tested for SARS-CoV-2 IgM and IgG antibodies by the enzyme-linked immunosorbent assay. Multivariate analysis was used to determine factors independently associated with SARS-CoV-2 seropositivity. A P-value of < 0.05 was considered statistically significant. Results: The mean age was 47.72 ± 17.92 years, with 57.14% (144) female. The seroprevalence of SARS-CoV-2 (IgG or IgM) was 67.90%. Thirty-nine (15.48%) out of 252 participants had both SARS-CoV-2 IgG and IgM antibodies. Multivariable logistic regression analysis showed that healthcare workers had significantly higher odds of SARS-CoV-2 seropositivity than non-healthcare workers (adjusted odds ratio [aOR] = 3.83, 95% confidence interval [CI]: 1.52–9.66; P = 0.004). Conclusion: Serological evidence of SARS-CoV-2 infection was observed in approximately two out of every three unvaccinated adults, indicating widespread previous exposure through natural infection in the study population by the first half of 2022. The predominance of SARS-CoV-2 IgG over IgM antibodies suggests that most infections occurred before sample collection and is consistent with declining community transmission during the study period. Healthcare worker status was independently associated with SARS-CoV-2 seropositivity, reinforcing the importance of strengthening infection prevention and control measures to protect frontline healthcare workers during future emerging infectious disease outbreaks. Supplementary Information: The online version contains supplementary material available at https://doi.org/10.1186/s12879-026-14139-z.
SN - 1471-2334
ER -