Seroprevalence of anti-SARS-CoV-2 IgG antibodies among vaccinated healthcare workers in Bamako, Mali

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Introduction: Like many other countries, Mali, a West African country, has encountered various obstacles in the fight against the transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Despite resource constraints, however, the country implemented containment strategies. Therefore, in early 2021, Mali initiated a vaccination campaign as a tangible defense against COVID-19, prioritizing the administration of the first vaccine doses to healthcare personnel. Consequently, we found assessing anti-SARS-CoV-2 IgG antibody levels important to gauge the efficacy of vaccines administered to frontline healthcare workers in Bamako, Mali. Methods: The study enrolled 172 vaccinated front-line healthcare workers from referral hospitals in Bamako, Mali, between March and June 2022. Serum samples were subjected to enzyme-linked immunosorbent assay (ELISA) to assess the levels of anti-SARS-CoV-2 IgG antibodies. Prevaccination serum samples served as controls. Chi-square and Mann-Whitney tests were used to compare proportions and means. Results: Among the 172 participants, 98.2% had high levels of anti-SARS-CoV-2 spike protein antibodies; only 1.6% (n=2) were seronegative. The majority, 62.2% (n=107), received a two-dose vaccination schedule, and the Astra Zeneca® vaccine was the most widely used (52.3%). The average level of postvaccine antibodies was significantly greater in participants who received two doses of vaccine than in those who received one dose (33.7 index vs. 29.1 index; p=0.02). Conclusions: Most healthcare workers exhibited favorable vaccine responses, as indicated by their positive reactivity to anti-SARS-CoV-2 IgG spike proteins. The nature and dosage of the vaccines influenced the antibody response, with a notable advantage observed for individuals who received a two-dose regimen. These findings underscore the importance of continuous research and evaluation to understand and enhance vaccine effectiveness.

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