Immunogenicity of Reduced-Dose Monovalent Type 2 Oral Poliovirus Vaccine in Mocuba, Mozambique

Abstract

Background 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: one-drop instead of two-drops. Methods We conducted a randomized, controlled, open-label, non-inferiority trial (10% margin) to compared immunogenicity following administration of one versus two-drops of mOPV2. We enrolled 9-22-months old infants from Mocuba district of Mozambique. Poliovirus neutralizing antibodies were measured in sera collected before and one 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 (number ACTRN12619000184178p). Results We enrolled 378 children and 262 (69%) completed per-protocol requirements. Immune response of mOPV2 was 53.6% (95% confidence interval [CI]: 44.9%-62.1%) and 60.6% (95% CI: 52.2%-68.4%) in 1-drop and 2-drops recipients, respectively. The non-inferiority margin of the 10% was not reached (difference=7.0%; 95%CI= -5.0-19.0). Conclusion A small loss of immunogenicity of reduced mOPV2 was observed. Although the non-inferiority 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.

Safety of the novel oral poliovirus vaccine type 2 (nOPV2) in infants and young children aged 1 to <5 years and lot-to-lot consistency of the immune response to nOPV2 in infants in The Gambia: a phase 3, double-blind, randomised controlled trial

“…A trial conducted in inactivated poliovirus vaccine vaccinated infants aged 11–18 months in Mozambique showed a type 2 seroconversion rate of 83 (60·6%) of 137 (95% CI 52·2–68·4) following two mOPV2 doses. 22 This finding contrasts with a seroconversion rate of 88 (92%) of 96 (95% CI 84–96) in historic control infants following one dose of mOPV2 in the study in Panama. 10 Thus, the immunogenicity of nOPV2 in this trial is consistent with data for mOPV2 from comparable settings in sub-Saharan Africa.…”

Risk factors for the spread of vaccine-derived type 2 polioviruses after global withdrawal of trivalent oral poliovirus vaccine and the effects of outbreak responses with monovalent vaccine: a retrospective analysis of surveillance data for 51 countries in Africa

“…Type 2 population immunity from OPV (OPV2) declined from a population-weighted median of 87% (IQR 81−93) of children under 5 years in January-June, 2016, to 14% (9-37) in January-June, 2020. In provinces where no mOPV2 has been used, median population immunity from trivalent OPV declined from 88% (IQR 83−92) in children under 5 years in January-June, 2016 to 10% (7)(8)(9)(10)(11)(12)(13)(14) in January-June, 2020 (figure 1). In provinces with mOPV2 use in the past 2 years, median OPV2 immunity was 70% (IQR 49−86).…”

“…To estimate per-dose OPV effectiveness, we used data on seroconversion after administration of trivalent OPV or mOPV2 from 38 studies across Africa and Asia, collected in a systematic review conducted in 2018. 9 , 10 , 11 , 12 , 13…”

“…To estimate per-dose OPV effectiveness, we used data on seroconversion after administration of trivalent OPV or mOPV2 from 38 studies across Africa and Asia, collected in a systematic review conducted in 2018. [9][10][11][12][13] Global surveillance for poliomyelitis is done through surveillance for acute flaccid paralysis. 14 For each individual with acute flaccid paralysis, information recorded includes the first and second administrative region (hereafter province and district, respectively) in which the individual resides, the date of onset of paralysis, the age and sex of the individual, and the reported number of OPV doses received.…”

Novel Oral Polio Vaccine Type 2 Use for Polio Outbreak Response: A Global Effort for a Global Health Emergency

“…Data from field use and clinical trials support the hypothesis that nOPV2 would have similar immunogenicity and effectiveness to OPV2. Although findings of reduced immunogenicity of nOPV2 in young children when co-administered with bOPV indicated that nOPV2 may be less robust to competition with other enteroviruses in the gut [ 23 ], a study in the Gambia demonstrated excellent seroconversion in infants and young children (63% post-dose 1 in infants seronegative at baseline [n = 499], 65% in children [n = 66]), at levels comparable to those observed in an mOPV2 trial in a similar setting in Mozambique (68% in children seronegative at baseline [n = 75]) [ 10 , 24 ]. In addition, two in-depth studies comparing mOPV2 and nOPV2 effectiveness in Nigeria, which experienced a large cVDPV2 outbreak in 2021 and used the most nOPV2 of any country, found no significant difference between the two vaccines used in outbreak response campaigns [ 19 , 20 ].…”