The goal of eradicating polio worldwide is within sight. But public health officials must make sure that vaccines administered after that point cannot cause a recurrence of the disease. Researchers in Britain have come up with a safe strain that would prevent polio reinfection.
Polio vaccines are stockpiled for use into the foreseeable future to prevent another epidemic of paralytic polio, once the disease is officially eradicated.
Experts say there is always a chance the live, weakened virus used to make the warehoused drugs could escape factories, risking new cases of polio. There have also been instances in which mutated viral strains survive in the gut of immune-compromised people after they have been vaccinated.
At the urging of the World Health Organization, British researchers have developed safe seed strains from which to make polio vaccine. They modified viral RNA to make the resulting strains genetically stable. The strains that are now used have in rare cases mutated into dangerous forms.
Vaccines made from the new seed strains would not pose a health hazard at manufacturing facilities, nor be dangerous if they entered into the environment, according to British National Institute for Biological Standards and Control Virology Division head Philip Minor. He helped develop the new strains for polio vaccine, which researchers describe in the journal PLOS Pathogens.
“In the very end-game period, more inactivated polio vaccine will be used because that is what you need to do to make sure... you have not missed anything, if you like. ... So, if you do that, and you use a very much safer strain, I think you are a bit more secure than if you go with what we have at the moment,” Minor said.
Vaccine is now made from live, weakened virus. Minor said the new vaccines would be as effective, but safer than current vaccine.
"And after polio is declared eradicated, I think inactivated polio vaccine will continue to be used for some time because of the possibility that you are wrong, that you have made a misstep, you have got chronically excreting, immuno-deficient people out there somewhere. I think there will be a need to carry on vaccination against polio until you are really sure what has happened, I think,” Minor said.
An expert WHO panel will make the final determination which new strains of inactivated polio virus are safe to put into new vaccines in the post-polio era.