(CNN) As the world works to produce an effective Covid-19 vaccine, some experts suggest an existing vaccine that almost everyone already gets might help.
There is plenty of evidence that existing vaccines such as polio vaccines protect children against a wide range of infections and it's worth trying them out against the new coronavirus, a team of experts wrote in Science magazine Thursday.
An oral polio vaccine is safe, cheap, easy to give and widely available, with more than 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.
It would make sense to at least test it to see if it helps against coronavirus, said Konstantin Chumakov of the FDA and Dr. Robert Gallo of the Institute of Human Virology at the University of Maryland School of Medicine, along with their colleagues.
Gallo co-discovered the virus that causes AIDS while Chumakov is associate director for research at the FDA's vaccine division.
"We propose the use of OPV (oral poliovirus vaccine ) to ameliorate or prevent COVID-19. Both poliovirus and coronavirus are positive-strand RNA viruses; therefore, it is likely that they may induce and be affected by common innate immunity mechanisms," they wrote. " ... Oral poliovirus vaccine in particular, could provide temporary protection against coronavirus disease."
The oral polio vaccine produces herd effects, they wrote. Herd immunity is reached when the majority of a given population -- 70% to 90% -- becomes immune to an infectious disease, either because they have become infected and recovered, or through vaccination.
In addition to protecting vulnerable individuals, it could also prevent the spread of the new coronavirus by increasing the proportion of unsusceptible individuals, Chumakov, Gallo and colleagues wrote.
"The risk of complications due to OPV is extremely low," they added. It can cause a polio-like complication, but only in about one out of every 3 million doses given, and then mostly in immunocompromised children.
Doctors know that the benefits of vaccination extend beyond the particular germs targeted.
"Other live attenuated viral vaccines such as those against measles and smallpox have also been associated with pronounced nonspecific protective effects against infectious diseases," they wrote.
"In Africa, when measles vaccine was introduced in the community, the overall mortality in children declined by more than 50%, a reduction that was far larger than anticipated on the basis of the protection against measles deaths alone," they added.
The OPV is no longer licensed or available in the United States, but is still used in some parts of the world, according to the Centers for Disease Control and Prevention. Children get vaccine doses by drops in the mouth.
Coronavirus has infected more than 2 million people in the United States and killed nearly 114,000. With constantly shifting timelines, no one's sure when a vaccine will be available, but the target is next year.
Vaccines in development around the world are in various stages of testing. Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said he's confident one of the vaccine candidates will be proven safe and effective by the first quarter of 2021.