Study confirms genetic stability of nOPV2

February 11, 2022 by PATH

nOPV2 is designed to hasten polio eradication

A new study published in npj Vaccines confirms that the novel oral polio vaccine against type 2 polio (nOPV2) is more stable against virulent mutations than the licensed oral polio vaccine against type 2 (OPV2). This is the first study that directly assesses shed nOPV2 virus against shed OPV2 virus in comparable groups. It adds to the evidence base that the attenuated nOPV2 vaccine is more resistant to reversion than OPV2.

“These findings represent a key milestone in the development of nOPV2,” says John Konz, nOPV project director at PATH, which serves as the convener of the nOPV development efforts. “They provide further proof that the designed modifications are working as intended, preventing the primary route by which the currently licensed OPV2 virus becomes more virulent.”

Improved genetic stability was the impetus behind the development of nOPV2. While currently licensed OPV2 is safe and effective, it evolves quickly and can, in rare cases, revert to a disease-causing form that can cause outbreaks in areas of low vaccination coverage: circulating vaccine-derived poliovirus outbreaks (cVDPV2). This is especially the case for the type 2 strain, and it represents a tenacious obstacle to polio eradication.

For nOPV2, researchers made modifications to key regions of the virus that make it less likely to revert and regain its ability to cause disease. “This work builds on several decades of insight into poliovirus and its vaccines,” says Andrew Macadam, a Principal Scientist at National Institute for Biological Standards and Control and one of nOPV2’s developers. “It gave us the opportunity to apply what we know to a make a better vaccine, and this study is a heartening indication that we have done so.”

In light of the promising data on nOPV2 and based on the urgent need to control cVDPVs, in November 2020, the vaccine became the first to receive a recommendation for initial use under WHO’s Emergency Use Listing (EUL) procedure. Data on real-world performance continue to reinforce a strong safety profile.

Because polio vaccines will be needed for years to come, PATH and partners are continuing to advance clinical research on nOPV2 with the goal of WHO prequalification, which will ensure long-term accessibility in the eradication and post-eradication era. PATH is also advancing novel OPVs for polio types 1 and 3.

For more information about nOPV2:

Fact sheet

Polio eradication and beyond: a long-term vaccine strategy