Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2025 Sep 1:127680.
doi: 10.1016/j.vaccine.2025.127680. Online ahead of print.

Kinetics and seroprevalence of anti-SARS-CoV-2 antibodies in vaccinated and unvaccinated health workers in Bamako, Mali, November 2021-February 2023

Saidou Balam  1 , Fousseyni Kane  2 , Bourama Traore  3 , Drissa Konate  2 , Fatimata A Diallo  2 , Housseini Dolo  2 , Anou Moise Somboro  2 , Ousmane Kodio  2 , Antieme Combo Georges Togo  2 , Bassirou Diarra  2 , Nathan C Incandela  4 , Fatoumata Diallo  2 , Abdouramane Traore  2 , Salimata Kante  2 , Merepen Dite Agnes Guindo  2 , Bourema Kouriba  5 , Yaya Ibrahim Coulibaly  3 , Ousmane Faye  3 , Seydou Doumbia  2 , Mahamadou Diakite  2
Affiliations
Free article

Kinetics and seroprevalence of anti-SARS-CoV-2 antibodies in vaccinated and unvaccinated health workers in Bamako, Mali, November 2021-February 2023

Saidou Balam et al. Vaccine. .
Free article

Abstract

Background: This prospective study aimed to evaluate the dynamics and seroprevalence of anti-SARS-CoV-2 antibodies in a cohort of vaccinated and unvaccinated health workers (HWs) in Bamako, Mali. The study also measured antibody responses as a function of SARS-CoV-2 infections, socio-demography, vaccination status and associated comorbidities.

Method: 685 vaccinated and 413 unvaccinated HWs (total = 1098) were monitored over a 15-month periods with follow-up visits every 3 months for the first 6 months and a final visit after 15 months. Anti-spike and anti-nucleoprotein antibodies were assessed using ELISA. Non-parametric tests and logistic regression analyses were performed to compare antibody levels and to investigate associated factors.

Results: Overall, anti-SARS-CoV-2 antibodies tended to increase over the first 3 months in both vaccinated and unvaccinated groups. Spike (>98 %) and nucleoprotein (>91 %) antibodies remained high and relatively stable after 3 months and correlated inversely with the rate attack of symptomatic and asymptomatic COVID-19. Males demonstrated lower antibody responses, particularly for nucleoprotein (p < 0.05) compared to females. HWs with comorbidities demonstrated higher antibody responses. Participants with active SARS-CoV-2 infections exhibited decreased antibody levels. Vaccinated participants exhibited a trend toward higher spike antibodies. Virus-inactivated type vaccination increased nucleoprotein antibodies. Furthermore, there was no increase of antibody levels after receiving, two or more vaccine doses, independently of whether the same or a different type of used vaccines. Nucleoprotein antibodies varied significantly at inclusion among participants across blood groups.

Conclusion: This study identified a progressive increase in anti-spike and anti-nucleoprotein antibodies in both vaccinated and unvaccinated HWs, correlating with reduced COVID-19 infection rates. These findings highlight the significance of both natural and vaccine-induced immunity and the need to assess antibody levels and long-term protection beyond the 15-month study period.

Keywords: Antibody dynamics; COVID-19 vaccines; Health workers; Mali; SARS-CoV-2.

PubMed Disclaimer

Conflict of interest statement

Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Saidou Balam reports financial support was provided by Bill & Melinda Gates Foundation. Saidou Balam reports administrative support, article publishing charges, equipment, drugs, or supplies, statistical analysis, travel, and writing assistance were provided by World Health Organization Regional Office for Africa. None If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

LinkOut - more resources