Review 2: "Monitoring the Risk of Type-2 Circulating Vaccine-Derived Poliovirus Emergence during Roll-Out of Type-2 Novel Oral Polio Vaccine"

Ali Faisal Saleem

doi:doi:10.1162/2e3983f5.30a9e054

Review 2: "Monitoring the Risk of Type-2 Circulating Vaccine-Derived Poliovirus Emergence during Roll-Out of Type-2 Novel Oral Polio Vaccine"

The reviews affirm nOPV2’s superior genetic stability, reducing cVDPV2 emergencies significantly compared to mOPV2.

by Ali Faisal Saleem

Published onNov 21, 2024

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This Pub is a Review of

Monitoring the Risk of Type-2 Circulating Vaccine-Derived Poliovirus Emergence during Roll-Out of Type-2 Novel Oral Polio Vaccine

by Corey M. Peak, Hil Lyons, Arend Voorman, Elizabeth J Gray, Laura V Cooper, Isobel M Blake, Kaija Hawes, and Ananda S Bandyopadhyay

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Published on Oct 17, 2024
www.medrxiv.org

Description

Abstract Background/Objectives Although wild poliovirus type 2 has been eradicated, prolonged transmission of the live-attenuated virus contained in the type-2 oral polio vaccine (OPV2) in under-immunized populations has led to emergence of circulating vaccine derived poliovirus type-2 (cVDPV2). The novel OPV2 (nOPV2) was designed to be more genetically stable and reduce the chance of cVDPV2 emergence while retaining comparable immunogenicity to the Sabin monovalent OPV2 (mOPV2). This study aims to estimate the relative reduction in the emergence risk due to use of nOPV2 instead of mOPV2.Methods Data on OPV2 vaccination campaigns from May 2016 to 1 August 2024 were analyzed to estimate type-2 OPV-induced immunity in children under 5 years of age. Poliovirus surveillance data were used to estimate seeding date and classify cVDPV2 emergences as Sabin- or novel-derived. The expected number of emergences if mOPV2 was used instead of nOPV2 was estimated accounting for the timing and volume of nOPV2 doses, the known emergence risk factors for emergence from mOPV2, and censoring due to the incomplete observation period for more recent nOPV2 doses.Results As of 1 August 2024, over 98% of the approximately 1.19 billion nOPV2 doses administered globally were in Africa. We estimate approximately 76 (95% confidence interval 69-85) index isolates of cVDPV2 emergences would be expected to be detected by 1 August 2024 if mOPV2 had been used instead of nOPV2 in Africa. The 18 observed nOPV2-derived emergences represent a 76% (74%-79%) lower risk of emergence by nOPV2 than mOPV2 in Africa. The crude global analysis produced similar results. Key limitations include the incomplete understanding of the drivers of heterogeneity in emergence risk across geographies and variance in the per-dose risk of emergence may be incompletely captured using known risk factors.Conclusions These results are consistent with the accumulating clinical and field evidence showing enhanced genetic stability of nOPV2 relative to mOPV2, and this approach has been implemented in near-real time to contextualize new findings during roll-out of this new vaccine. While nOPV2 has resulted in new emergences of cVDPV2, the number of cVDPV2 emergences is estimated to be approximately four-fold lower than if mOPV2 had been used instead.

RR\ID Evidence Scale rating by reviewer:

Strong. The main study claims are very well-justified by the data and analytic methods used. There is little room for doubt that the study produced has very similar results and conclusions as compared with the hypothetical ideal study. The study’s main claims should be considered conclusive and actionable without reservation.

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Review: The analysis presented is both thoughtful and relevant to current discussions in the field. The authors meticulously examine the emergence of OP2, specifically highlighting the differences between the novel oral poliovirus vaccine type 2 (nOPV2) and the traditional Sabin vaccine.

The data clearly indicates that the genetic stability of nOPV2 is significantly better than that of Sabin OPV, and the occurrences of emergencies were also fewer.

How did the emergencies differ? What was the mean duration of these two vaccine-related emergencies?

How were the emergencies managed? Are different tools used to control these situations?

How many children or adults were infected per vaccine dose?

Were the emergencies different in terms of magnitude and/or impact? What was the severity level of these emergencies (medium, high, low)?

Can the author identify or describe the financial impact of these two emergencies? Are there differences in the economic impact on the countries involved compared to outbreak control organizations?

Although the nOPV2 has not been used in any other part of Asia or in any other regions, will there be a difference in emergencies if it is adopted in Asia compared to areas where it has not been used?

Review 2: "Monitoring the Risk of Type-2 Circulating Vaccine-Derived Poliovirus Emergence during Roll-Out of Type-2 Novel Oral Polio Vaccine"

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