Background : The COVID-19 pandemic, caused by the SARS-CoV-2 virus, affected hundreds of millions of people worldwide and resulted in significant mortality. In Senegal, over 89,000 infections and nearly 2000 deaths were reported. The deployment of the Johnson & Johnson (adenoviral vector) and Sinopharm (inactivated virus) vaccines through the COVAX initiative and bilateral partnerships was crucial in mitigating the spread of the virus. However, little local data existed regarding their immunogenicity. This study aimed to evaluate the humoral immune response induced by the Johnson & Johnson and Sinopharm COVID-19 vaccines among Senegalese adults aged 18 years and older over a 12-month period. Methods : This longitudinal multicentre study was conducted between August 2022 and August 2023 with 375 adult volunteers. Plasma samples were collected and tested using the Q-Plex SARS-CoV-2 Human IgG (5-plex) kit to quantify antibodies targeting the S1, S2, and NP proteins of SARS-CoV-2. Follow-up visits were scheduled based on the vaccine received: Johnson & Johnson vaccine recipients had 7 time points (Day 0, Day 14, Day 28, Month 3, Month 6, Month 9, and Month 12), while Sinopharm vaccine recipients had 8 time points (Day 0, Day 14, Day 28(Day 0B), Day 14B, Day 28B, Month 6, Month 9, and Month 12). Analysis of antibody levels was stratified by vaccine type, age, sex, and period of sampling after vaccination. Results : Both vaccines elicited detectable antibody responses, albeit with disparate dynamics. Johnson & Johnson induced a stronger response (S1: 490.66, S2: 1068.12, NP: 161.45) in young adults aged 18 - 30 years, while Sinopharm showed a better initial response (S1: 868.61, S2: 1608.58, NP: 310.88) in older individuals (46 - 70 years). However, antibody levels declined progressively in both groups over time (from S1: 465.99, S2: 1003, NP: 157.98 to S1: 210.01, S2: 466.88, NP: 141.39 and from S1: 451.36, S2: 1075.51, NP: 207.39 to S1: 446.74, S2: 631.09, NP: 142.59). Notably, women demonstrated more persistent antibody responses than men. Strong associations were observed between antibody positivity and sociodemographic factors such as household size, occupation, and formal educational level. Conclusion : This study confirms the immunogenicity of both Johnson & Johnson and Sinopharm vaccines in the Senegalese population, with appreciable levels of antibody production that gradually wane over time, supporting the need for booster doses to sustain long-term immunity. Differences in antibody responses by age, sex, and vaccine type highlight the role of individual and contextual factors. These findings underscore the importance of tailoring vaccination strategies and serological monitoring to local realities.
KeywordsCOVID-19Vaccination
World Health Organization. WHO Coronavirus (COVID-19) Dashboard. https://data.who.int/dashboards/covid19
World Health Organization. COVID-19 Dashboard—Senegal. https://data.who.int/dashboards/covid19?m49=686
Africa News (2025) Africa COVID-19 Stats: 874,036 Cases; 18,498 Deaths; 524,557 recoveries. Africa News. https://www.africanews.com/2020/07/29/coronavirus-in-africa-breakdown-of-infected-virus-free-countries/
Chu, D.K., Duda, S., Solo, K., Yaacoub, S. and Schunemann, H. (2020) Physical Distancing, Face Masks, and Eye Protection to Prevent Person-to-Person Transmission of SARS-CoV-2 and COVID-19: A Systematic Review and Meta-Analysis. Journal of Vascular Surgery , 72, Article 1500. https://doi.org/10.1016/j.jvs.2020.07.040
Ford, N., Holmer, H.K., Chou, R., Villeneuve, P.J., Baller, A., Van Kerkhove, M., et al . (2021) Mask Use in Community Settings in the Context of COVID-19: A Systematic Review of Ecological Data. eClinicalMedicine , 38, Article 101024. https://doi.org/10.1016/j.eclinm.2021.101024
Catching, A., Capponi, S., Yeh, M.T., Bianco, S. and Andino, R. (2021) Examining the Interplay between Face Mask Usage, Asymptomatic Transmission, and Social Distancing on the Spread of COVID-19. Scientific Reports , 11, Article No. 15998. https://doi.org/10.1038/s41598-021-94960-5
Rader, B., White, L.F., Burns, M.R., et al . (2021) Mask-Wearing and Control of SARS-CoV-2 Transmission in the USA: A Cross-Sectional Study. The Lancet Digital Health , 3, E148-E157. https://www.thelancet.com/journals/landig/article/PIIS2589-7500(20)30293-4/fulltext
WHO (2021) Les différents types de vaccins contre la COVID-19. https://www.who.int/fr/news-room/feature-stories/detail/the-race-for-a-covid-19-vaccine-explained
Angeli, F., Spanevello, A., Reboldi, G., Visca, D. and Verdecchia, P. (2021) SARS-CoV-2 Vaccines: Lights and Shadows. European Journal of Internal Medicine , 88, 1-8. https://doi.org/10.1016/j.ejim.2021.04.019
Park, H., Park, M.S., Seok, J.H., You, J., Kim, J., Kim, J., et al . (2022) Insights into the Immune Responses of SARS-CoV-2 in Relation to COVID-19 Vaccines. Journal of Microbiology , 60, 308-320. https://doi.org/10.1007/s12275-022-1598-x
Yuan, Y., Cao, D., Zhang, Y., Ma, J., Qi, J., Wang, Q., et al . (2017) Cryo-EM Structures of MERS-CoV and SARS-CoV Spike Glycoproteins Reveal the Dynamic Receptor Binding Domains. Nature Communications , 8, Article No. 15092. https://doi.org/10.1038/ncomms15092
Humoral Response
Johnson & Johnson
Sinopharm
Kinetics
Adult Cohort
Senegal
Longitudinal Study
Wrapp, D., Wang, N.S., Corbett, K.S., et al . (2020) Cryo-EM Structure of the 2019-nCoV Spike in the Prefusion Conformation. Science , 367, 1260-1263.
Yaugel-Novoa, M., Bourlet, T. and Paul, S. (2022) Role of the Humoral Immune Response during COVID-19: Guilty or Not Guilty? Mucosal Immunology , 15, 1170-1180. https://doi.org/10.1038/s41385-022-00569-w
Institute for Health Metrics and Evaluation (2024) COVID-19 Vaccine Efficacy Summary. https://www.healthdata.org/research-analysis/diseases-injuries/covid/covid-19-vaccine-efficacy-summary
Mbow, M., de Jong, S.E., Meurs, L., Mboup, S., Dieye, T.N., Polman, K., et al . (2014) Changes in Immunological Profile as a Function of Urbanization and Lifestyle. Immunology , 143, 569-577. https://doi.org/10.1111/imm.12335
Amoah, A.S., Obeng, B.B., May, L., Kruize, Y.C., Larbi, I.A., Kabesch, M., et al . (2014) Urban-Rural Differences in the Gene Expression Profiles of Ghanaian Children. Genes & Immunity , 15, 313-319. https://doi.org/10.1038/gene.2014.21
Xia, S., Zhang, Y., Wang, Y., Wang, H., Yang, Y., Gao, G.F., et al . (2021) Safety and Immunogenicity of an Inactivated SARS-CoV-2 Vaccine, BBIBP-CorV: A Randomised, Double-Blind, Placebo-Controlled, Phase 1/2 Trial. The Lancet Infectious Diseases , 21, 39-51. https://doi.org/10.1016/s1473-3099(20)30831-8
Sadoff, J., Gray, G., Vandebosch, A., Cárdenas, V., Shukarev, G., Grinsztejn, B., et al . (2021) Safety and Efficacy of Single-Dose Ad26.COV2.S Vaccine against Covid-19. New England Journal of Medicine , 384, 2187-2201. https://doi.org/10.1056/nejmoa2101544
Madewell, Z.J., Yang, Y., Longini, I.M., Halloran, M.E. and Dean, N.E. (2020) Household Transmission of SARS-CoV-2: A Systematic Review and Meta-Analysis. JAMA Network Open , 3, e2031756. https://doi.org/10.1001/jamanetworkopen.2020.31756
Pollán, M., Pérez-Gómez, B., Pastor-Barriuso, R., et al . (2020) Prevalence of SARS-CoV-2 in Spain (ENE-COVID): A Nationwide, Population-Based Seroepidemiological Study. The Lancet , 396, 535-544.
Mutambudzi, M., Niedzwiedz, C., Macdonald, E.B., Leyland, A., Mair, F., Anderson, J., et al . (2020) Occupation and Risk of Severe COVID-19: Prospective Cohort Study of 120 075 UK Biobank Participants. Occupational and Environmental Medicine , 78, 307-314. https://doi.org/10.1136/oemed-2020-106731
Goldstein, E., Lipsitch, M. and Cevik, M. (2021) On the Effect of Age on the Transmission of SARS-CoV-2 in Households, Schools, and the Community. The Journal of Infectious Diseases , 223, 362-369. https://doi.org/10.1093/infdis/jiaa691
Park, Y.J., Choe, Y.J., Park, O., Park, S.Y., et al . (2020) Contact Tracing during Coronavirus Disease Outbreak, South Korea, 2020. Emerging Infectious Diseases , 26, 2465-2468.
Assis, R., Jain, A., Nakajima, R., Jasinskas, A., Khan, S., Palma, A., et al . (2021) Distinct SARS-CoV-2 Antibody Reactivity Patterns Elicited by Natural Infection and mRNA Vaccination. npj Vaccines , 6, Article No. 132. https://doi.org/10.1038/s41541-021-00396-3
Vaughan, A., Duffell, E., Freidl, G.S., Lemos, D.S., Nardone, A., Valenciano, M., et al . (2023) Systematic Review of Seroprevalence of SARS-CoV-2 Antibodies and Appraisal of Evidence, Prior to the Widespread Introduction of Vaccine Programmes in the WHO European Region, January-December 2020. BMJ Open , 13, e064240. https://doi.org/10.1136/bmjopen-2022-064240
Krammer, F., Srivastava, K., Alshammary, H., Amoako, A.A., et al . (2021) Antibody Responses in Seropositive Persons after a Single Dose of SARS-CoV-2 mRNA Vaccine. The New England Journal of Medicine , 384, 1372-1374.
Barouch, D.H., Stephenson, K.E., Sadoff, J., et al. (2021) Durable Humoral and Cellular Immune Responses Following Ad26.COV2.S Vaccination for COVID-19. New England Journal of Medicine . https://doi.org/10.1101/2021.07.05.21259918
Massachusetts Medical Society (2021) Réponses immunitaires humorales et cellulaires durables 8 mois après la vaccination contre l’Ad26.COV2.S. New England Journal of Medicine , 385, 951-953. https://www.nejm.org/doi/full/10.1056/NEJMc2108829
Townsend, J.P., Hassler, H.B., Sah, P., Galvani, A.P. and Dornburg, A. (2022) The Durability of Natural Infection and Vaccine-Induced Immunity against Future Infection by SARS-CoV-2. Proceedings of the National Academy of Sciences , 119, e2204336119. https://doi.org/10.1073/pnas.2204336119
Zhang, J., Xia, Y., Liu, X. and Liu, G. (2023) Advanced Vaccine Design Strategies against SARS-CoV-2 and Emerging Variants. Bioengineering , 10, 148. https://doi.org/10.3390/bioengineering10020148
Dan, J.M., Mateus, J., Kato, Y., et al . (2021) Immunological Memory to SARS-CoV-2 Assessed for up to 8 Months after Infection. Science , 371, eabf4063.
Zhang, Z., Mateus, J., Coelho, C.H., Dan, J.M., Moderbacher, C.R., Gálvez, R.I., et al . (2022) Humoral and Cellular Immune Memory to Four COVID-19 Vaccines. Cell , 185, 2434-2451.e17. https://doi.org/10.1016/j.cell.2022.05.022
Self, W.H., Tenforde, M.W., Rhoads, J.P., et al . (2021) Comparative Effectiveness of Moderna, Pfizer-BioNTech, and Janssen (Johnson & Johnson) Vaccines in Preventing COVID-19 Hospitalizations among Adults Without Immunocompromising Conditions. The Morbidity and Mortality Weekly Report , 70, 1337-1343.
Krammer, F. (2020) SARS-CoV-2 Vaccines in Development. Nature , 586, 516-527. https://doi.org/10.1038/s41586-020-2798-3
Chi, X., Yan, R., Zhang, J., Zhang, G., Zhang, Y., Hao, M., et al . (2020) A Neutralizing Human Antibody Binds to the N-Terminal Domain of the Spike Protein of SARS-CoV-2. Science , 369, 650-655. https://doi.org/10.1126/science.abc6952
Goel, R.R., Painter, M.M., Apostolidis, S.A., et al . (2021) mRNA Vaccines Induce Durable Immune Memory to SARS-CoV-2 and Variants of Concern. Science , 374, abm0829.
Khoury, D.S., Cromer, D., Reynaldi, A., Schlub, T.E., Wheatley, A.K., Juno, J.A., et al . (2021) Neutralizing Antibody Levels Are Highly Predictive of Immune Protection from Symptomatic SARS-CoV-2 Infection. Nature Medicine , 27, 1205-1211. https://doi.org/10.1038/s41591-021-01377-8
Sahin, U., Muik, A., Derhovanessian, E., et al . (2020) COVID-19 Vaccine BNT162b1 Elicits Human Antibody and TH1 T Cell Responses. Nature , 586, 594-599.
Victora, G.D. and Nussenzweig, M.C. (2022) Germinal Centers. Annual Review of Immunology , 40, 413-442. https://doi.org/10.1146/annurev-immunol-120419-022408
Gaebler, C., Wang, Z., Lorenzi, J.C.C., Muecksch, F., Finkin, S., Tokuyama, M., et al . (2021) Evolution of Antibody Immunity to SARS-CoV-2. Nature , 591, 639-644. https://doi.org/10.1038/s41586-021-03207-w
Collier, D.A., Ferreira, A.T.M., Kotagiri, P., et al . (2021) Age-Related Immune Response Heterogeneity to SARS-CoV-2 Vaccine BNT162b2. Nature , 596, 417-422.
Müller, L., Andrée, M., Moskorz, W., Drexler, I., Walotka, L., Grothmann, R., et al . (2021) Age-Dependent Immune Response to the Biontech/Pfizer BNT162b2 Coronavirus Disease 2019 Vaccination. Clinical Infectious Diseases , 73, 2065-2072. https://doi.org/10.1093/cid/ciab381
Klein, S.L. and Flanagan, K.L. (2016) Différences entre les sexes dans les réponses immunitaires. Nature Reviews Immunology , 16, 626-638. https://www.nature.com/articles/nri.2016.90
Fink, A.L. and Klein, S.L. (2015) Sex and Gender Impact Immune Responses to Vaccines among the Elderly. Physiology , 30, 408-416. https://doi.org/10.1152/physiol.00035.2015
Fischinger, S., Boudreau, C.M., Butler, A.L., Streeck, H. and Alter, G. (2019) Sex Differences in Vaccine-Induced Humoral Immunity. Seminars in Immunopathology , 41, 239-249. https://doi.org/10.1007/s00281-018-0726-5
Takahashi, T., Ellingson, M.K., Wong, P., et al . (2020) Sex Differences in Immune Responses That Underlie COVID-19 Disease Outcomes. Nature , 588, 315-320.
Fujigaki, H., Yamamoto, Y., Koseki, T., Banno, S., Ando, T., Ito, H., et al . (2022) Antibody Responses to BNT162b2 Vaccination in Japan: Monitoring Vaccine Efficacy by Measuring IgG Antibodies against the Receptor-Binding Domain of SARS-CoV-2. Microbiology Spectrum , 10, e01181. https://doi.org/10.1128/spectrum.01181-21
Mukherjee, S. and Pahan, K. (2021) Is COVID-19 Gender-Sensitive? Journal of Neuroimmune Pharmacology , 16, 38-47. https://doi.org/10.1007/s11481-020-09974-z
Ruggieri, A., Anticoli, S., D’Ambrosio, A., Giordani, L. and Viora, M. (2016) The Influence of Sex and Gender on Immunity, Infection and Vaccination. Annali dell ’ Istituto Superiore di Sanità , 52, 198-204.
Mishra, S.K., Pradhan, S.K., Pati, S., Sahu, S. and Nanda, R.K. (2021) Waning of Anti-Spike Antibodies in AZD1222 (ChAdOx1) Vaccinated Healthcare Providers: A Prospective Longitudinal Study. Cureus , 13, e19879. https://doi.org/10.7759/cureus.19879
Farid, E., Herrera-Uribe, J. and Stevenson, N.J. (2022) The Effect of Age, Gender and Comorbidities Upon SARS-CoV-2 Spike Antibody Induction after Two Doses of Sinopharm Vaccine and the Effect of a Pfizer/BioNtech Booster Vaccine. Frontiers in Immunology , 13, Article 817597. https://doi.org/10.3389/fimmu.2022.817597
Shao, T., Verma, H.K., Pande, B., Costanzo, V., Ye, W., Cai, Y., et al . (2021) Physical Activity and Nutritional Influence on Immune Function: An Important Strategy to Improve Immunity and Health Status. Frontiers in Physiology , 12, Article 751374. https://doi.org/10.3389/fphys.2021.751374
Smith, T.P., Kennedy, S.L. and Fleshner, M. (2004) Influence of Age and Physical Activity on the Primary in Vivo Antibody and T Cell-Mediated Responses in Men. Journal of Applied Physiology , 97, 491-498. https://doi.org/10.1152/japplphysiol.01404.2003