SARS-CoV-2 seroprevalence and COVID-19 vaccination coverage in two states of Nigeria from a population based household survey

Abstract

SARS-CoV-2 population-based seroprevalence surveys are useful for estimating the extent of SARS-CoV-2 infections, which may be underestimated by COVID-19 case counts. Surveys conducted in October 2020 in four Nigerian states showed that SARS-CoV-2 seroprevalence ranged from 9.3% in Gombe (northeast) to 25.2% in Enugu (southeast) after the first COVID-19 wave, more than 100 and 700 times higher than the official number of COVID-19 cases in these two states, respectively. We conducted a serosurvey after the second COVID-19 wave to evaluate the extent of SARS-CoV-2 infections, attitudes to COVID-19 vaccines, and COVID-19 vaccination coverage in two regions of Nigeria. Using the World Health Organization (WHO) Unity protocol, 34 enumeration areas (EAs) each in the Federal Capital Territory (FCT) (Northcentral Zone) and Kano State (Northwest Zone) were sampled in June 2021, using probability proportional to estimated size; 20 households in one EA were randomly selected. All consenting and assenting members of a household were asked about risk behaviors; adults who were 18 years and above (the eligible population for COVID-19 vaccination in Nigeria) responded to questions on COVID-19 vaccine attitudes and receipt. Blood and nasal/oropharyngeal samples were taken from all consenting and assenting household members. Blood samples collected were tested with the Luminex xMAP® SARS-CoV-2 Multi-Antigen IgG Assay and swabs by reverse-transcriptase-PCR (RT-PCR). Overall response rates were 76.8% in the FCT (n = 1,505 blood draws) and 80.4% in Kano State (n = 2,178 blood draws). Following the second COVID-19 wave in Nigeria, more than 40% of residents in the FCT (40.3%, 95% CI: 34.7–45.9) and Kano State (42.6%, 95% CI: 39.4–45.8) had evidence of prior SARS-CoV-2 infection. There were no active SARS-CoV-2 infections detected by RT-PCR in either the FCT or Kano State. In the FCT and Kano State, 3.4% and 1.6% of people surveyed reported receipt of any COVID-19 vaccine, three months after vaccines were available in country. In the FCT, 77.5% of adults were aware of COVID-19 vaccines, of whom 46.9% reported willingness to receive them. In Kano State, 48.7% of adults were aware of COVID-19 vaccines, of whom 61.1% were willing to receive them. In both regions, about 84% of those reporting unwillingness to accept COVID-19 vaccines cited concerns over vaccine safety. “Serosurvey findings revealed that SARS-CoV-2 infection was far more widespread in both the Federal Capital Territory and Kano State than indicated by reported case numbers. Despite high awareness, COVID-19 vaccine uptake remained low, primarily due to concerns about vaccine safety. These results highlight the urgent need for targeted risk communication to address vaccine hesitancy and improve coverage. Serosurveys provide valuable insights that can guide public health interventions and future pandemic preparedness in Nigeria.”