Study of SARS-CoV-2 antibody prevalence in Sierra Leone suggests far higher numbers than currently

Harvard Medical School

This article is part of Harvard Medical School’s continuing coverage of medicine, biomedical research, medical education, and policy related to the SARS-CoV-2 pandemic and the disease COVID-19.

  • By HALEY BRIDGER | Brigham and Women’s Hospital

In the first nationally representative SARS-CoV-2 antibody survey from sub-Saharan Africa published to date, researchers found evidence of significant underreporting of COVID-19 cases. The survey, conducted in Sierra Leone and based on data collected in March 2021, presents evidence of large-scale underreporting of cases and low vaccination rates. Results of the study were published in BMJ Global Health.

“Our findings remind us that there still may be significant underreporting of COVID-19 in various countries throughout the region,” said corresponding author Eugene Richardson, assistant professor of global health and social medicine in the Blavatnik Institute at Harvard Medical School and an infectious disease physician in the Division of Global Health Equity at Brigham and Women’s Hospital. “There are still likely significant portions of the population that don’t have acquired immunity to infection with earlier SARS-CoV-2 variants, and there are still very low vaccination rates in the region. This means populations may be at higher risk for severe illness if infected with the omicron variant.”

Findings from this study include:

  • Underreporting. More than 200,000 people had previously been infected, 43 times higher than the reported number of cases.
  • Low acquired immunity. As of March 2021, 2.6 percent of the population had previously been infected, with urban areas having twice as many cases as rural areas.
  • Low vaccination rates. As of Dec. 8, 2021, less than 5 percent of Sierra Leoneans had been fully vaccinated.

At the current vaccination rate, the researchers noted, it will take several more years to vaccinate the whole population.

Together, these findings are cause for grave concern, according to Richardson, who has been working as an advisor to the Africa Centres for Disease Control and Prevention on the COVID-19 pandemic.

“We are calling for more rapid vaccine deployments in countries like Sierra Leone as part of global vaccine justice, including support for intellectual property waivers and technology transfers,” he said.

“We hope this study also encourages other nations to conduct serosurveys since they can provide data vital to understanding the pandemic’s progression.”

This study was supported by NIAID K08 AI139361, NIH/NIGMS R01 GM130900, the Sierra Leone Ministry of Health and Sanitation, and the Africa CDC.

Adapted from a Brigham and Women’s news release.

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