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Oral Polio Vaccine (OPV) to Mitigate the Risk of Illness and Mortality During the COVID-19 Pandemic: A Cluster-Randomised Trial in Guinea-Bissau
22 Pages Posted: 21 Jun 2022
More...Abstract
Background: Oral Polio Vaccine (OPV) may strengthen the immune system broadly improving resistance to non-polio-infections. Prior to COVID-19 vaccines being widely available, we tested if OPV could reduce the risk of illness and mortality.
Methods: We conducted an unblinded cluster-randomised trial. Houses in urban Guinea-Bissau were randomised 1:1 to intervention or control. Residents aged 50+ years were invited to participate. Participants received bivalent OPV (single dose) or nothing and were followed for 6 months. Rates of mortality, admissions, and consultation for infections (primary composite outcome) were compared in Cox proportional hazards models adjusted for age and area of residence. Secondary outcomes included mortality, admissions, consultations, and symptoms of infection.
Findings: Among 3729 enrolled participants, we followed 3726 (OPV: 1580; Control: 2146) and registered 66 deaths, 97 admissions and 298 consultations for infections. OPV did not reduce the risk of the composite outcome, hazard ratio (HR)=0.97 (95%CI: 0.79-1.18). The effect differed by sex (HR=0.71 (0.51-0.98) for men; HR=1.18 (0.91-1.52) for women; p for same effect=0.02) and by BCG scar-status (HR=0.70 (0.49-0.99) in scar-positive; HR=1.13 (0.89-1.45) in scar-negative participants; p=0.03). OPV had no overall significant effect on mortality (HR=0.96 (0.59-1.55)), admissions (HR=0.76 (0.49-1.17)) or recorded consultations (HR=0.99 (0.79-1.25)). Only 2/590 participants with reported COVID-19 test stated positive results. OPV was associated with increased reporting of symptoms of infection (6050 episodes; HR=1.10 (1.03-1.17)).
Interpretation: OPV increased reported symptoms of infections but did not increase the risk of severe infections. OPV appeared to benefit men and BCG-scar positive participants.
Trial Registration: Registration: www.clinicaltrials.gov/NCT04445428
Funding: University of Southern Denmark supported the trial. ABF was supported by an Ascending investigator grant from Lundbeck Foundation (R313-2019-635) and a Sapere Aude grant from Independent Research Fund Denmark (9060-00018B).
Declaration of Interest: The authors have no conflicts of interest.
Ethical Approval: The trial was approved by the Comité Nacional de Ética na Saúde, Guinea-Bissau on 21 May 2020 (Ref: 077/CNES/INASA/2020) and received consultative approval from The National Committee on Health Research Ethics, Denmark on 16 June 2020 (Ref: 2008258).
Keywords: Oral Polio Vaccine, Non-specific (heterologous) effects of vaccine, mortality, morbidity
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