Polio vaccine may offer limited protection: Scientists

New Delhi : Indian scientists have responded cautiously to a suggestion by global researchers that the oral polio vaccine be tested for COVID-19, saying it is a "testable idea" based on a sound scientific concept but may offer only limited protection against the infection.

With a vaccine for COVID-19 at least a year away, scientists say repurposing already safe and effective vaccines is the way to go for immediate relief against COVID-19.

The repurposed vaccines could include the oral polio vaccine (OPV) and the Bacillus Calmette–Guerin (BCG) used against tuberculosis, both part of the immunisation given to Indian children.

It is worth conducting a clinical trial, said Ram Vishwakarma, director of the CSIR-Indian Institute of Integrative Medicine (CSIR-IIIM) in Jammu.

He was responding to a study last week by an international team of researchers in the journal Science. The researchers, including Shyamasundaran Kottili and Robert Gallo from the University of Maryland School of Medicine in the US, said the OPV should be tested to see if it might protect people from the SARS-CoV-2 virus.

They noted that the vaccine used to prevent poliomyelitis infections has been around since the 1950s, and is found to provide some protection against other viral infections.

The stimulation of innate immunity by attenuated vaccines -- live but with substantially reduced virulence -- in general and OPV in particular could provide temporary protection against COVID-19, the scientists noted.

Innate immunity is one of the two main immunity strategies found in vertebrates, including humans.

According to Vishwakarma, the idea proposed by Gallo, an internationally renowned virologist who co-discovered that HIV causes AIDS, is based on the fact that people who have undergone polio vaccination boost their innate immunity.

"It is a sound scientific concept but we do not know what will eventually happen because this has multiple phases. It may help patients in the early phase, with mild and moderate symptoms but may not help serious patients," Vishwakarma told PTI.

"It is a testable idea based on a scientific hypothesis that is in turn based on the concept of what we call trained immunity, a non-specific way to boost innate immunity for our immune system to fight out the virus," Vishwakarma explained.

India has been implementing a pulse polio programme since 1995 with an aim to eradicate polio, added virologist Upasana Ray. This is in accordance with a resolution passed by the World Health Assembly in 1988 for polio eradication globally.

"Every year, children between 0-5 years age are immunised with polio vaccine. It is a very widespread and well established programme," Ray, senior scientist at CSIR-IICB, Kolkata, told PTI.

Immunologist Satyajit Rath added that it is best to keep in mind that Gallo and his team are not talking about the function of the OPV as a ''vaccine'' which generates a specific immune response.