Scientists from the UK’s Medicines and Healthcare products Regulatory Agency (MHRA) have jointly led an international study validating the genetic stability of the novel oral polio vaccine type 2 (nOPV2), a key tool in global polio eradication efforts. The study was published on 19 January 2026 in Nature Microbiology.
Conducted in collaboration with research institutions in Uganda, the UK, Israel, France, the Netherlands, the US and the World Health Organization, the study examined how nOPV2 evolves after use in real-world vaccination campaigns. The findings show that the vaccine is significantly more genetically stable than earlier oral polio vaccines and is effectively interrupting outbreaks while reducing the risk of new vaccine-derived poliovirus strains.
Researchers analysed 231 poliovirus type 2 samples collected from stool and sewage in Uganda between January 2022 and March 2023, following nationwide nOPV2 campaigns. The analysis found that the vaccine’s engineered genetic modifications, particularly those stabilising the main attenuation domain, successfully limited harmful mutations seen with older vaccines.
The study did identify a rare recombinant strain formed through interaction with other circulating enteroviruses. While this strain showed increased neurovirulence in laboratory tests, it did not spread widely, likely due to high vaccination coverage during the campaign period.
Uganda was able to interrupt circulating vaccine-derived poliovirus transmission after two nationwide nOPV2 campaigns that reached around 20 million children, reinforcing the vaccine’s effectiveness under field conditions.
MHRA’s WHO Global Specialised Polio Laboratory played a central role in the research, carrying out whole-genome sequencing using advanced Illumina and Oxford Nanopore technologies and analysing virus samples from both clinical and environmental sources. The work was supported by funding from the National Institute for Health Research, MHRA core funding, and the Bill & Melinda Gates Foundation.
The findings strengthen confidence in nOPV2 as a safer and more stable oral polio vaccine and support its continued use alongside inactivated polio vaccines, robust immunisation programmes and strong surveillance systems to achieve and sustain global polio eradication.
