Seroprevalence of anti-SARS-CoV-2 antibodies in a population living in Bomassa village, Republic of Congo

Abstract

Objectives : As limited data are available from Central Africa, the aim of the present study was to evaluate the anti-SARS-CoV-2 Ab prevalence in indigenous residents, in Bomassa, a village located in the Sangha Region in the Republic of Congo. Methods : Plasma and oropharyngeal swabs samples were collected from 304 healthy adult individuals, randomly recruited in May 2021 before vaccine introduction in the area. In addition, 82 plasma samples from the same area in 2019 were included as controls for cross-reaction investigation against other Coronaviruses. The SARS-CoV-2 virus was detected by qRT-PCR and sequenced using Next-Generation Sequencing. ELISA method was used for detecting IgG, IgM and neutralizing Ab against SARS-CoV-2 antigens. Results : About 4.9% (15/304) of the participants were SARS-CoV-2 positive and B.1.631 was the only variant identified. Of 109 individuals harboring anti-SARS-CoV-2 IgG and/or IgM Ab, 45.9 % (50/109) had anti-SARS-CoV-2 neutralizing Ab. A proportion of 3.7% (3/82) of control samples collected before the pandemic were positive to IgG, but negative for neutralizing Ab. Conclusions : While seroprevalence against SARS-CoV-2 represented 25% in indigenous population, almost 50% of seropositive participants had neutralizing antibodies. This finding highlights that the spread of the SARS-COV2 infection is under-estimate in the country.

Profile of Serological (IgM/IgG) and Virological Markers of COVID-19 in Some Private Universities in Cameroon During the Pandemic

“…We noted a predominance of IgG (24.40 %) compared to IgM (20.62 %). Similar trends have already been reported with higher IgG level in the general population in USA [31], Cameroon [7], [32], [33], [34], Congo [35], India [36] and Brazil [37] as well as in students in Spain [38]. In fact, experience earned from the kinetics of antibody response from other viral infections taught us that unlike IgM that appears in the acute phase of infection, IgG is the marker of the chronic infection and should appear later on in greater amount.…”

“…Four serological profiles were identified: 12.71% IgM-/IgG+, 11.68% IgM+/IgG+, 8.93% of IgM+/IgG-, 66.67 % of IgM-/IgG-. Similar results have been reported in Congo [35], in the USA [31], and in Cameroon [32], [33] with a sample size of 684, 368, 291 and 971 respectively. No association has been found between serological profiles and all the socio-demographic characteristics.…”

The Lancet Commission on lessons for the future from the COVID-19 pandemic

“…A serosurvey in six districts of Zambia showed that the case ascertainment rate was only one reported case per 92 actual infections, or 1·1%. 183 Similar findings apply to other countries—such as the Republic of the Congo, 184 the Democratic Republic of the Congo, 185 Malawi, 186 and Kenya 187 —suggesting that up to 80% of the population had already been infected by COVID-19 before the arrival of the omicron variant.

Figure 10 Estimated cumulative infections and estimated daily infections in the African region, Feb 4, 2020–May 31, 2022 Data from the Institute for Health Metrics and Evaluation, accessed May 31, 2022.

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Assessment of neutralizing antibody responses after natural SARS-CoV-2 infection and vaccination in congolese individuals

“…We aimed to assess the neutralizing capacity induced by vaccination and natural infection by using a standardize commercial surrogate virus neutralization test (sVNT) [17]. The sVNT has been designed as a powerful alternative to the conventional plaque reduction neutralization test (PRNT) to measure neutralizing antibodies post-infection to SARS-CoV-2 [19][20][21][22], and in vaccinated individuals [23][24][25]. In addition, the design of the GenScript sVNT ELISA is adapted to determine the difference in binding inhibition to compare vaccines and infecting SARS-CoV-2 variants antibody responses.…”