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Efficacy of the oral pentavalent rotavirus vaccine in Mali
Samba O Sow1, Milagritos Tapia, Fadima C Haidara
1Centre pour le Développement des Vaccins, Bamako, Mali. ssow@medicine.umaryland.edu
Insights
The pentavalent rotavirus vaccine (PRV) showed low efficacy in Mali during its first year due to reporting challenges. After adjustments, the vaccine demonstrated improved efficacy and strong immunogenicity in Malian infants.
Area of Science:
- Pediatrics
- Infectious Diseases
- Vaccinology
- Public Health
Background:
- Rotavirus gastroenteritis (RVGE) is a significant cause of severe diarrheal disease in infants globally.
- The pentavalent rotavirus vaccine (PRV) has been developed to prevent RVGE.
- Assessing vaccine efficacy in diverse settings, like sub-Saharan Africa, is crucial for global health strategies.
Purpose of the Study:
- To evaluate the efficacy of the pentavalent rotavirus vaccine (PRV) against severe rotavirus gastroenteritis (RVGE) in infants in Mali.
- To assess the immunogenicity of the PRV in the Malian infant population.
- To report on the safety profile of the PRV in the study participants.
Main Methods:
- A randomized, placebo-controlled field trial involving 1960 infants in Mali.
- Infants received three doses of PRV or placebo at approximately 6, 10, and 14 weeks of age.
- Severe RVGE was defined using the Vesikari Clinical Scoring System (≥11); data collection adapted to local healthcare-seeking behaviors.
Main Results:
- Initial efficacy estimates in the first year were unreliable (per-protocol: 1%; intention-to-treat: 42.9%) due to cultural practices.
- Following surveillance system modifications, per-protocol efficacy against severe RVGE in the second year was 19.2%.
- High seroresponse rates were observed in PRV recipients (82.5%) compared to placebo (20.0%), with significantly higher antibody titers.
Conclusions:
- The pentavalent rotavirus vaccine (PRV) demonstrated significant immunogenicity in Malian infants.
- Vaccine efficacy against severe rotavirus gastroenteritis (RVGE) was challenging to ascertain initially but improved after adapting surveillance methods.
- No serious adverse events were attributed to the vaccine, indicating a favorable safety profile.
Abstract:
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.
