Novel Polio Vaccine Matches Traditional in Immune Response

Medscape

10-06-2025

The novel oral polio vaccine type 2 (nOPV2) induced intestinal mucosal immune responses comparable to those induced by the traditional Sabin monovalent oral polio vaccine type 2 (mOPV2) across different age groups, with the strongest responses observed in infants.
METHODOLOGY:
The novel nOPV2 is a more genetically stable vaccine and carries a lower risk of reverting to neurovirulence than mOPV2 and has been deployed to interrupt vaccine-derived poliovirus type 2 outbreaks.
Researchers compared intestinal mucosal immune responses induced by the first dose of nOPV2 and mOPV2 across different age groups: Infants aged 18-22 weeks, children aged 1-4 years, and adults aged 18-50 years.
They included participants from four clinical trials: 47 infants, 47 children, and 66 adults enrolled in the nOPV2 trials, and 42 infants, 46 children, and 100 adults in the mOPV2 control trials.
They used serum samples collected on day 0 (the day of the nOPV2 or mOPV2 challenge) and on day 28 to measure poliovirus type 2-specific serum neutralization.
They used stool samples collected daily for the first 10 days and then weekly from day 14 to day 28 for the evaluation of viral shedding.
TAKEAWAY:
Overall, both nOPV2 and mOPV2 induced similar intestinal poliovirus type 2-specific neutralization and immunoglobulin A responses on day 14 across all age groups, with no significant differences observed between the two vaccines.
Among OPV2-naive participants who received nOPV2, an age-related decline in response rates was observed: 82% of infants, 61% of children, and 25% of adults showed detectable poliovirus type 2-specific neutralization on day 14.
Among children, nOPV2 recipients showed higher viral shedding rates than mOPV2 recipients (92% vs 44%; P < .0001), potentially due to differences in prior vaccine exposure; however, no differences in viral shedding rates were observed among adults or infants.
< .0001), potentially due to differences in prior vaccine exposure; however, no differences in viral shedding rates were observed among adults or infants. Adults with prior OPV2 exposure showed lower viral shedding rates than OPV2-naive adults (20% vs 82%; P < .0001) when challenged with nOPV2, despite similar neutralizing activity and immunoglobulin A responses.
IN PRACTICE:
'This study's findings affirm the utility of nOPV2 as an important tool to address the ongoing cVDPV2 [type 2 circulating vaccine-derived poliovirus] outbreaks,' the study authors wrote.
SOURCE:
The study was led by Audrey Godin, MD, London School of Hygiene & Tropical Medicine, London, England. It was published online on April 30, 2025, in The Lancet Microbe .
LIMITATIONS:
A significant limitation was the time gap between the mOPV2 trials conducted in 2015-2016 and the nOPV2 trials conducted in 2018-2019. The lack of stool samples after day 14 prevented the study of long-term mucosal immunity. Additionally, as the study focused on fully vaccinated healthy infants, young children, and adults, the results may not be generalizable to immunodeficient individuals, older children, adolescents, unvaccinated or incompletely immunized individuals, or populations in countries with different socioeconomic conditions.
DISCLOSURES:
This study was funded by the Bill & Melinda Gates Foundation and Japan Agency for Medical Research and Development. The authors declared having no conflicts of interest.