Post-Omicron SARS-CoV-2 serostatus in Sierra Leone: A cross-sectional study in a maternity hospital setting in Freetown, November/December 2022.

BACKGROUND

Spread of SARS-CoV-2 in Sub-Saharan African countries has been poorly investigated, especially in the later pandemic stages. We aimed to assess the post-Omicron situation in Sierra Leone in November/December 2022 considering SARS-CoV-2 serostatus, vaccinations, and behavioral factors.

METHODS

In a cross-sectional study conducted in a maternity hospital in Freetown, Sierra Leone, both patients and staff provided dried blood spot samples for analysis of anti-S and anti-N IgG prevalence using Anti-SARS-CoV-2-ELISA. Additionally, we collected sociodemographic and infection-related information through questionnaires. Outcome parameters included seropositivity, infection-related seroprevalence, and self-reported vaccination status. We used logistic regression to identify associations with prior infection and with vaccination status.

RESULTS

Out of 791 participants (389 patients, 402 staff), 670 (84.7 %) displayed a positive SARS-CoV-2 serostatus resulting from either infection or vaccination. Among a sub-sample of 514 participants within which determination of prior natural infection was possible, 441individuals (85.8 %) were affected. Prior infection was associated with female sex and tertiary education level. Overall, 60.3 % reported having been vaccinated. Staff as opposed to patients, and individuals with higher socioeconomic status were more likely to report vaccination. Individuals who assessed their risk of COVID-19 as either higher or lower compared to a medium-level risk were more likely to have contracted the virus and less likely to have received vaccination.

CONCLUSION

Our findings suggest that since the Omicron wave in 2022, the Sierra Leonean population has almost universally been exposed to SARS-CoV-2. While this is encouraging in the light of relatively low excess mortality in the country, future investigations on the long-term effect of high viral exposure on epidemic resilience and public health impact will be crucial.