Available polio vaccines not optimal for safety: Study

While the whole world is striving for polio virus eradication, a recent study has raised concerns about post-eradication manufacturing and stockpiling vaccine stores containing live virus that could escape and repopulate the environment.

The new study found that different types of polio vaccines currently exist, but none are optimal from a safety point of view. Live attenuated (weakened) vaccine strains carry genetic mutations that prevent them from causing disease, but they can--in rare cases--revert to more dangerous (or virulent) virus.

To improve safety, WHO has strongly encouraged new manufacturers to switch the source of inactivated virus from virulent wild-type strains to an attenuated strain named after the polio vaccine pioneer Sabin.

Arguing that the attenuated Sabin strain is unstable and, therefore, potentially problematic, Philip Minor from the National Institute for Biological Standards and Control in Potters Bar, UK, and colleagues presented data on alternative attenuated strains which they propose as a safer alternative source for inactivated vaccine.

Researchers examined their ability to grow in tissue culture (necessary for vaccine production), their risk for causing paralysis in mice engineered to carry a human polio-virus receptor and whether--after inactivation--they effectively immunized rats.

Finally it was shown that these new strains were unable to infect primates by mouth. In all these tests, the new strains behaved as predicted, that is, they are effective, suitable to mass production and safer than the alternatives.

The study is published in the Journal PLOS Pathogens.