High seroprevalence of anti-SARS-CoV-2 antibodies in the capital of Chad

Abstract

Background. Since the start of the COVID-19 pandemic, Chad has had 7,417 confirmed cases and 193 deaths, one of the lowest in Africa. Objective. This study assessed SARS-CoV-2 immunity in N’Djamena. Methods. In August-October 2021, eleven N’Djamena hospitals collected outpatient data and samples. IgG antibodies against SARSCoV- 2 nucleocapsid protein were identified using ELISA. “Bambino Gesù” Laboratory, Rome, Italy, performed external quality control with chemiluminescence assay. Results. 25-34-year-old (35.2%) made up the largest age group at 31.9 12.6 years. 56.4% were women, 1.3 women/men. The 7th district had 22.5% and the 1st 22.3%. Housewives and students dominated. Overall seroprevalence was 69.5% (95% CI: 67.7-71.3), females 68.2% (65.8-70.5) and males 71.2% (68.6-73.8). >44-year-old had 73.9% seroprevalence. Under-15s were 57.4% positive. Housewives (70.9%), civil servants (71.5%), and health workers (9.7%) had the highest antibody positivity. N’Djamena’s 9th district had 73.1% optimism and the 3rd district had 52.5%. Seroprevalences were highest at Good Samaritan Hospital (75.4%) and National General Referral Hospital (74.7%). Conclusion. Our findings indicate a high circulation of SARSCoV- 2 in N’Djamena, despite low mortality and morbidity after the first two COVID-19 pandemic waves. This high seroprevalence must be considered in Chad’s vaccine policy.

Presence of neutralizing SARS‐CoV‐2 antibodies in asymptomatic population of N'Djamena, Chad

“…For the immune‐comparative analysis, 260 samples of the overall epidemiological survey carried out in a previous study, 21 were selected and analyzed using CLIA (Roche), ECLIA (Roche), and CMIA (Abbott) and confirmed with the anti‐Spike pseudotyped VSV assay. The average age of the participants was 34.3 ± 12.9 years, ranging from 10 to 86 years, female gender represented 52.7% (137/260), for a male/female ratio of 1.1.…”

“…Given that in the previous study, 21 on the aforementioned cohort the SARS‐CoV‐2 positive rate, using IgG antibodies against SARSCoV‐2 nucleocapsid protein ELISA kits, was 69.5%, we focused our study on the identification of the presence of NAbs in a selected seropositive group of this population. Considering the role of such antibodies in conferring potential protection to Covid‐19 and to future possible coronavirus‐related diseases, we compared in this study four different kits including the pseudotype assay, which is the gold standard for NAbs detection.…”

“…Considering the role of such antibodies in conferring potential protection to Covid‐19 and to future possible coronavirus‐related diseases, we compared in this study four different kits including the pseudotype assay, which is the gold standard for NAbs detection. According to the previous study 21 the selected 260 samples were distributed as follows: anti‐N positive (210 samples), anti‐N equivocal (28 samples). A group of negative anti‐N samples (22 samples) was included as a control.…”

Launch of the Laboratory for Major Tropical Epidemics (LAGET) in Chad: Strengthening the capacity for epidemiological surveillance, monitoring and diagnosis of endemic or emerging infectious diseases in Central Africa

“…The LAGET has developed its immunoassay branch to determine the immunological status of patients with respect to numerous infectious agents, and consequently has contributed to several biomedical studies concerning the SARS-CoV-2 seroprevalence or the production of protective antibodies following COVID-19 vaccination campaigns in Chad (16).…”