Key result
Administration of 1 drop of mOPV2 did not meet the 10% noninferiority margin for immune response compared to 2 drops (53.6% vs 60.6%; difference 7.0%, 95% CI -5.0% to 19.0%).
Why the study?
The monovalent type 2 oral poliovirus vaccine stockpile is low, and administering a reduced dose of 1 drop instead of 2 is a potential strategy to stretch supplies.
Does 1 drop of mOPV2 provide noninferior immunogenicity compared to 2 drops in infants aged 9-22 months?
RCT (n=378)
Open-label
Does 1 drop of mOPV2 provide noninferior immunogenicity compared to 2 drops in infants aged 9-22 months?
Effect estimate: difference 7.0% (95% CI -5.0% to 19.0%)
Absolute Event Rate: 53.6% vs 60.6%
A reduced 1-drop dose of mOPV2 failed to meet noninferiority criteria for immunogenicity compared to the standard 2-drop dose, though it may still be considered as a dose-sparing measure in severe shortages.
1-drop mOPV2 is not noninferior for immunogenicity; supports retaining 2-drop dosing absent further trials.
BACKGROUND: The monovalent type 2 oral poliovirus vaccine (mOPV2) stockpile is low. One potential strategy to stretch the existing mOPV2 supply is to administer a reduced dose: 1 drop instead of 2. METHODS: We conducted a randomized, controlled, open-label, noninferiority trial (10% margin) to compared immunogenicity after administration of 1 versus 2 drops of mOPV2. We enrolled 9-22-month-old infants from Mocuba district of Mozambique. Poliovirus neutralizing antibodies were measured in serum samples collected before and 1 month after mOPV2 administration. Immune response was defined as seroconversion from seronegative (<1:8) at baseline to seropositive (≥1:8) after vaccination or boosting titers by ≥4-fold for those with titers between 1:8 and 1:362 at baseline. The trial was registered at anzctr.org.au (no. ACTRN12619000184178p). RESULTS: We enrolled 378 children, and 262 (69%) completed per-protocol requirements. The immune response of mOPV2 was 53.6% (95% confidence interval, 44.9%-62.1%) and 60.6% (52.2%-68.4%) in 1-drop and 2-drop recipients, respectively. The noninferiority margin of the 10% was not reached (difference, 7.0%; 95% confidence interval, -5.0% to 19.0%). CONCLUSION: A small loss of immunogenicity of reduced mOPV2 was observed. Although the noninferiority target was not achieved, the Strategic Advisory Group of Experts on Immunization recommended the 1-drop strategy as a dose-sparing measure if mOPV2 supplies deteriorate further.
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Deus et al. (2020) conducted an RCT in Poliovirus immunization (n=378). Monovalent type 2 oral poliovirus vaccine (mOPV2) vs. 2 drops was evaluated on Immune response (seroconversion from seronegative to seropositive or boosting titers by ≥4-fold) (difference 7.0%, 95% CI -5.0% to 19.0%). Administration of 1 drop of mOPV2 did not meet the 10% noninferiority margin for immune response compared to 2 drops (53.6% vs 60.6%; difference 7.0%, 95% CI -5.0% to 19.0%).
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