Environmental Surveillance for Risk Assessment in the Context of a Phase 2 Clinical Trial of Type 2 Novel Oral Polio Vaccine in Panama

Abstract

Environmental surveillance was recommended for risk mitigation in a novel oral polio vaccine-2 (nOPV2) clinical trial (M5-ABMG) to monitor excretion, potential circulation, and loss of attenuation of the two nOPV2 candidates. The nOPV2 candidates were developed to address the risk of poliovirus (PV) type 2 circulating vaccine-derived poliovirus (cVDPV) as part of the global eradication strategy. Between November 2018 and January 2020, an environmental surveillance study for the clinical trial was conducted in parallel to the M5-ABMG clinical trial at five locations in Panama. The collection sites were located upstream from local treatment plant inlets, to capture the excreta from trial participants and their community. Laboratory analyses of 49 environmental samples were conducted using the two-phase separation method. Novel OPV2 strains were not detected in sewage samples collected during the study period. However, six samples were positive for Sabin-like type 3 PV, two samples were positive for Sabin-like type 1 PV, and non-polio enteroviruses NPEVs were detected in 27 samples. One of the nOPV2 candidates has been granted Emergency Use Listing by the World Health Organization and initial use started in March 2021. This environmental surveillance study provided valuable risk mitigation information to support the Emergency Use Listing application.

Fecal Shedding of 2 Novel Live Attenuated Oral Poliovirus Type 2 Vaccine Candidates by Healthy Infants Administered Bivalent Oral Poliovirus Vaccine/Inactivated Poliovirus Vaccine: 2 Randomized Clinical Trials

“…There are several indications that this was due to low-level sample contamination during processing of stool samples, leading to aberrant laboratory results due to the high sensitivity of the RT-PCR assays. These include the first nOPV2-positive samples being obtained within 8 days of the first vaccination with low-dose nOPV2-c1), there being no geographic relationship between vaccine use and baseline positive infants, and environmental surveillance of the study area did not find any type 2 positive samples [ 20 ]. Furthermore, most positive samples were nOPV2-c1 despite the simultaneous use of nOPV2-c2.…”

The role of a genetically stable, novel oral type 2 poliovirus vaccine in the poliomyelitis endgame

“…Shedding analysis showed that nOPV2 was more genetically stable and had a lower risk of reverting to virulence – the cause of outbreaks of cVDPV – compared with mOPV2 ( 13 ). Also, nOPV2 could not be detected in wastewater in the neighborhoods close to the trial sites ( 14 ). WHO authorized the use of nOPV2 to control outbreaks of cVDPV2 through its Emergency Use Listing (EUL) procedure in November 2020 after the phase 2 studies were completed.…”