An oral polio vaccine is safe, cheap, easy to give and widely available, with over 1 billion doses produced and used annually in more than 140 countries, according to the team, which includes one of the scientists who discovered HIV and a vaccine expert from the Food and Drug Administration. The vaccine has nearly eradicated polio worldwide.

The oral polio vaccine uses a weakened version of the polio virus. The live attenuated vaccines produce a strong and long-lasting immune response, vaccine experts said. They’re slower to manufacture than modern vaccines that just use a piece of genetic material from a virus, and the US and European companies working on coronavirus vaccines are focusing on quicker ways.