Results
Overall, 10,386 individuals were enrolled in the survey. Of these, 9,180 (88.7%) completed an interview, 10,071 (97.0%) completed a blood draw, and 9,686 (93.3% of 10,071) had results from both antibody assays. In total of 9,332 (89.9% of 10,386) participants who had valid results from both assays as well as valid age and sex data were included in the analysis (Appendix Figure 1). From both assays, 4,738 (50.8%) participants tested negative, 1,023 (10.9%) tested positive, and 3,571 had discordant results resulting in a concordance of 61.7% and a kappa of 0.19 (Appendix Table 2). The WANTAI assay produced more positive results than the Abbott assay (4,280 (45.8%) vs. 1,337 (14.3%)).
Approximately half of the participants were female (51.2%, or 3,548) and were age 15-25 years (48.8% or 4,529). All participants who enrolled were Cameroonians, and the majority had completed secondary education (43.1%) (Table 1). Only 9.2% of participants reported co-morbid medical conditions (Table 1). Almost half of the participants age ≥15 years (43.7% or 3,351 of 8,399) reported being unemployed. The majority of those who were employed, worked in the informal trade sector (17.0%) (Table 1).
The overall weighted and adjusted seroprevalence of SARS-CoV-2 among those aged 5+ years across the 10 regional capitals of Cameroon was 10.5% (95% confidence interval [CI]: 9.1%-12.0%) among participants ≥5 years (Table 2). The seroprevalence was higher among males than it was among females [13.1% (95% CI: 11.5%-14.9%) vs. 8.0% (95% CI: 6.8%—9.3%); p<0.0001). Seroprevalence also differed by location (p=0.0062), ranging from 7.5% (95% CI: 5.9%-9.5%) in the East region to 12.4% in the Far North (95% CI: 10.4%-14.8%) and North West (95% CI: 10.5-14.7) regions. Across age groups, seroprevalence ranged from 7.9% (95% CI: 5.9%-10.7%) among participants 5-14 years, to 19.2% (95% CI: 14.7%-24.8%) among those aged 60 years and above. Among those who reported a comorbidity at the time of testing, 15.8% (95% CI: 12.8%-19.4%) were seropositive. Further, among participants who were diabetic at the time of testing, 24.2% (95% CI: 15-4%-36.0%) tested positive for SARS-CoV-2 antibodies. Among participants who had reported recent travel, 15.9% (95% CI:11.6%-21.5%) of those who had reported recent international travel were seropositive and 11.9% (95% CI:10.6%-13.4%) of participants who had reported recent domestic travel were seropositive (Table 2).
In the multivariable analysis females had a significantly lower seroprevalence than males (adjusted odds ratio [aOR]: 0.61, 95% CI: 0.51-0.74). Further, participants residing in the North (OR: 0.54 [95% CI: 0.30-0.99], Adamawa (aOR: 0.62 [95% CI: 0.41-0.94]), the East (aOR: 0.57 [95% CI: 0.40-0.82]), and Littoral (aOR: 0.60 [95% CI: 0.40-0.88]) regions had a lower seroprevalence compared to those in the South West (Table 2). The odds of having tested positive for this virus were also significantly higher across older age groups (as compared to children ages 5-14 years); (aOR: 1.15 [95% CI: 0.12-10.76), for those ages 15-25 years and aOR: 1.72 [95% CI: 0.21-14.25) for persons aged 26-35 years). Seroprevalence was higher among participants who reported having ever tested SARS CoV-2 positive (aOR: 3.61 [95% CI:2.01-6.47]), and among participants who traveled internationally in the past year compared to those who did not travel at all within the past year (aOR: 1.56 [95% CI: 1.10-2.22]). In multivariable analyses, seroprevalence did not differ by residential setting (urban vs. rural), history of comorbidities, or household size.
Based on the seroprevalence results from the study, we estimated that over 2 million persons were seropositive for SARS-CoV-2 (cumulatively) in the 10 regional capitals of Cameroon during October to December 2020, as compared to 21,160 cases officially reported at that time (Table 3).18 We estimate that one laboratory-confirmed case was reported for every 110 SARS-CoV-2 infections across the 10 regional capitals. The highest number of SARS-CoV-2 infections was estimated to be in Center region with an estimated 475,000 infections, and the lowest number in Adamawa with an estimated 64,700 infections.