SARS-CoV-2 seroprevalence at urban and rural sites in Kaduna State, Nigeria, during October/November 2021, immediately prior to detection of the Omicron variant
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Abstract
Background
Nigeria is Africa’s most populated country. By November 2021 it had experienced three waves of SARS-CoV-2 infection. Peer-reviewed seroprevalence data assessing the proportion of the Nigerian population that have been infected were extremely limited.
Methods
We conducted a serosurvey in one urban site (n = 400) and one rural site (n = 402) in Kaduna State, Nigeria between 11 October 2021 and 8 November 2021. Z-tests were used to compare seroprevalence across age groups, locations and sexes. T tests were used to determine whether age or household size are associated with seropositivity. Associations between seropositivity and recent history of common Covid-19 symptoms were tested using logistic regression.
Results
SARS-CoV-2 antibodies were detected in 42.5% an 53.5% of participants at the urban and rural sites, respectively The overall age- and sex- stratified seroprevalence was 43.7% (42.2% for unvaccinated individuals). The data indicate an infection rate in Kaduna State ≥359-fold the rate derived from polymerase chain reaction-confirmed cases. In the urban site, seroprevalence among females and participants aged <20 was lower than other groups. Reporting loss of sense of taste and/or smell was strongly associated with seropositive status. Associations with seropositivity were also found for the reporting of dry cough, fever, headache, nausea and sore throat.
Conclusions
This study provides baseline SARS-CoV-2 seroprevalence in Kaduna State, Nigeria, immediately prior to the spread of the Omicron variant. It indicates that in October/November 2021, approximately 56% of the population did not have detectable antibodies, and population subgroups with particularly low seroprevalence remain. It highlights limitations in using PCR-confirmed cases to estimate infection rates. The data will inform public health strategies in Nigeria and other sub-Saharan African countries with limited SARS-CoV-2 seroprevalence data.
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SciScore for 10.1101/2021.12.21.21268166: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Ethics Consent: Informed consent was confirmed via signatures or thumb prints, while parental consent was obtained for participants who were less than 18 years old. Sex as a biological variable not detected. Randomization not detected. Blinding not detected. Power Analysis not detected. Table 2: Resources
Antibodies Sentences Resources The presence of IgM antibodies indicates a recent infection (7-28 days prior to sampling), while IgG antibodies typically appear approximately 14 days after infection and endure for at least several months, providing some degree of immunity from further infection. IgMsuggested: NoneResults from OddPub: We did not detect open data. We also did not detect open code. Researchers …
SciScore for 10.1101/2021.12.21.21268166: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Ethics Consent: Informed consent was confirmed via signatures or thumb prints, while parental consent was obtained for participants who were less than 18 years old. Sex as a biological variable not detected. Randomization not detected. Blinding not detected. Power Analysis not detected. Table 2: Resources
Antibodies Sentences Resources The presence of IgM antibodies indicates a recent infection (7-28 days prior to sampling), while IgG antibodies typically appear approximately 14 days after infection and endure for at least several months, providing some degree of immunity from further infection. IgMsuggested: NoneResults from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).
Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:Other caveats include those individuals who are unable to mount a detectable antibody response, and the fact that SARS-CoV-2 antibody titres have been shown to decline in the months following exposure. Due to the delay between exposure and development of SARS-CoV-2 antibodies, it is likely the seropositive participants of this survey will have been infected by or vaccinated against the virus by 27 September 2021 (two weeks prior to the commencement of sampling). Across the two sites examined in this study, the overall seroprevalence was 48.0%, and the seroprevalence among unvaccinated participants was 45.4%. If the seroprevalence data reported here is representative of Kaduna State (population 8.25 million13), it would indicate at least 3.75 million SARS-CoV-2 infections since the pandemic began: a figure 387 times greater than the state’s 9,695 confirmed cases as of 27 September 202113. Extrapolating to the whole of Nigeria (population 213 million), this would suggest at least 96.7 million infections. This is in stark contrast to the number of confirmed cases at that time: 206,13813. During sample and data collection, the proportion of the Nigerian population who had received at least one dose of a SARS-CoV-2 vaccine was between 2.3% and 2.7%2. Self-reporting of vaccination in this survey indicated that 8.25% of participants in Kaduna City and 4.0% of participants in Kofar-Gayan had received at least one dose of a vaccine. This indicates that participants were not representa...
Results from TrialIdentifier: No clinical trial numbers were referenced.
Results from Barzooka: We did not find any issues relating to the usage of bar graphs.
Results from JetFighter: We did not find any issues relating to colormaps.
Results from rtransparent:- Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
- Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
- No protocol registration statement was detected.
Results from scite Reference Check: We found no unreliable references.
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