SARS-CoV-2 infection and antibody seroprevalence in routine surveillance patients, healthcare workers and general population in Kita region, Mali: an observational study 2020-2021.

OBJECTIVE: To estimate the degree of SARS-CoV-2 transmission among healthcare workers (HCWs) and general population in Kita region of Mali. DESIGN: Routine surveillance in 12 health facilities, HCWs serosurvey in five health facilities and community serosurvey in 16 villages in or near Kita town, Mali. SETTING: Kita region, western Mali; local health centres around the central (regional) referral health centre. PARTICIPANTS: Patients in routine surveillance, HCWs in local health centres and community members of all ages in populations associated with study health centres. MAIN OUTCOME MEASURES: Seropositivity of ELISA test detecting SARS-CoV-2-specific total antibodies and real-time RT-PCR confirmed SARS-CoV-2 infection. RESULTS: From 2392 routine surveillance samples, 68 (2.8%, 95% CI: 2.2% to 3.6%) tested positive for SARS-CoV-2 by RT-PCR. The monthly positivity rate was 0% in June-August 2020 and gradually increased to 6% by December 2020 and 6.2% by January 2021, then declined to 5.5%, 3.3%, 3.6% and 0.8% in February, March, April and May 2021, respectively. From 397 serum samples collected from 113 HCWs, 175 (44.1%, 95% CI: 39.1% to 49.1%) were positive for SARS-CoV-2 antibodies. The monthly seroprevalence was around 10% from September to November 2020 and increased to over 40% from December 2020 to May 2021. For community serosurvey in December 2020, overall seroprevalence of SARS-CoV-2 antibodies was 27.7%. The highest age-stratified seroprevalence was observed in participants aged 60-69 years (45.5%, 95% CI: 32.3% to 58.6%). The lowest was in children aged 0-9 years (14.0%, 95% CI: 7.4% to 20.6%). CONCLUSIONS: SARS-CoV-2 in rural Mali is much more widespread than assumed by national testing data and particularly in the older population and frontline HCWs. The observation is contrary to the widely expressed view, based on limited data, that COVID-19 infection rates were lower in 2020-2021 in West Africa than in other settings.

Efficacy of the oral pentavalent rotavirus vaccine in Mali.

The oral, pentavalent rotavirus vaccine (PRV), RotaTeq was assessed for prevention of severe rotavirus gastroenteritis (RVGE) in young children in two multi-site, randomized, placebo-controlled field trials; one in Asia (Vietnam and Bangladesh) and the other in sub-Saharan Africa (Ghana, Kenya and Mali). The efficacy results for the Mali site of the multi-country trial are presented here. We randomly assigned infants in a 1:1 ratio to receive 3 doses of PRV/placebo at approximately 6, 10, and 14 weeks of age. Gastroenteritis episodes were captured passively at the local health centers and by home visits. The primary study outcome was severe RVGE, as defined by a score of ≥ 11 using the Vesikari Clinical Scoring System occurring ≥ 14 days after the third dose until the end of the study. Other efficacy analyses included efficacy against severe RVGE through the first year and during the second years of life, as well as efficacy after receiving at least one dose of vaccine. In total, 1960 infants were enrolled in the trial at the Mali site and sera were collected on a subset of infants (approximately 150) for immunogenicity testing. In the first year of follow-up, largely due to cultural practices to visit traditional healers as the first point of care, the point estimate of efficacy was unreliable: the per protocol vaccine efficacy against severe RVGE was 1% (95% confidence interval [CI]: -431.7, 81.6); the intention-to-treat vaccine efficacy was 42.9% (95% CI: -125.7, 87.7). During the second year of follow-up, after the surveillance system was modified to adapt to local customs and health care seeking practices, the point estimate of per-protocol vaccine efficacy was 19.2% (95% CI: -23.1,47.3%). 82.5% of Malian infants (95% CI: 70.1,91.3%) who received PRV mounted a seroresponse (≥ 3-fold rise from baseline (prevaccination) to post-dose 3 vaccination) of anti-rotavirus immunoglobulin A antibody, with a post third-dose geometric mean titer (GMT) of 31.3 units/mL. By contrast, only 20.0% of placebo recipients (95% CI: 10.0, 33.7%) developed a seroresponse and the post-third dose GMT was 3.2 units/mL. None of the serious clinical adverse events observed were considered to be vaccine-related.