Abstract
Background Anti-SARS-CoV-2 vaccine remains a global health priority but there is scarcity of evidence on post-vaccine response from sub-Saharan Africa countries. Our objective was to assess the overall rate of SARS-CoV-2 immunity and its association according to vaccine-status and types of vaccines administered in the Cameroonian context.
Methods A population-based sero-survey was conducted from February through July-2022 among individuals screened for COVID-19 at the Chantal BIYA International Reference Centre-(CIRCB) in Yaoundé-Cameroon. Socio-demographic, clinical features and vaccine status were collected; SARS-CoV-2 antibodies were tested on plasma using Ninonasal™ COVID-19 IgG/IgM assay. Statistical analyses were performed, with p<0.05 statistically significant.
Results Of the 1713 participants enrolled, median [IQR] age was 39 [31–48], 57.1% (978/1713) men, 1.6% (27/1713) had flu-like symptoms and 19.7% (337/1713) had previously SARS-CoV-2 positive. Regarding vaccination, 67.6% (1158/1713) had received at least one dose (48.5% Pfizer, 24.9% Johnson&Johnson, 18.0% Moderna; 7.8% AstraZeneca, 4.4% Sinopharm and 0.2% Sputnik-light), of whom 91.9% (1064/1158) fully vaccinated. Median duration post-vaccination was 5 [3–8] months (min: 1; max: 20). Overall rate of anti-SARS-CoV-2 antibodies was 83.9% (1438/1713), with 0.2% (3/1713) IgM, 80.6% (1381/1713) IgG and 3.2% (54/1713) IgM/IgG. Following univariate analysis, the presence of antibodies was associated with female gender (F/M, p=0.028), vaccination (Yes/No, p<0.0001), complete and partial vaccination (p<0.0001 and p=0.008 respectively), duration post-vaccination (≤5/>5months, p<0.0001), as well as with all COVID-190 vaccines except sinopharm and sputnik (p<0.0001, p=0.0002, p<0.0001, p=0.024, p=0.5 and p=0.94 respectively). Following multivariate analysis, being vaccinated and duration post-vaccination (≤5months) were predictors of the presence of anti-SARS-CoV-2 antibodies (aOR=3.13 [95%CI: 2.39–4.09]; p=0.0001 and aOR=2.5 [95%CI: 1.63–3.84]; p<0.0001 respectively).
Conclusion The high-rate of COVID-19 antibodies suggests herd immunity at community-level in Cameroon following vaccination. However, rapid fading of antibodies (~5months) calls for strategies to adjust timing for booster-doses while phasing-out vaccines with poor immunity.
