Researchers have found genomic evidence to propose that the oral polio vaccine probably has been protecting young people from COVID-19 in India, which has recorded 8,088,000 infection cases and more than 121,000 deaths. As per the study, it happens through a process called cross-protection.
As per the researchers, the long-term immune response developed by the oral polio vaccine might also protect people from novel Coronavirus due to the biological similarities it shares with the vaccine type I and II viruses. Researchers associated with the National Institute of Immunology said in the paper—'Impact of Microbiota: A Paradigm for Evolving Herd Immunity against Viral Diseases'—that while the world has a severe infection with the novel Coronavirus, the death rate among the infected children under 10 is very low in India.
The authors of the study said that the children who have received regular immunization of different vaccines may have developed protection against the SARS-CoV-2 caused disease COVID-19. They also noted that in India, the mass polio vaccination program, as well as immunization with BCG, and measles vaccine has established memory responses against several types of variable antigens in the body.
The study also noted that "a single-type or multiple-types of antibodies from the pool of the antibody mixture, present in the body, can recognize the novel pathogens carrying the same or similar types of antigens." As per the researchers, this is a major reason behind the unexpectedly low rate of Coronavirus occurrence with a faster recovery rate in India, a country with approximately 1.33 billion people.
Based on the findings the study authors concluded that herd immunity is the most critical preventive intervention, delivering protective immunity against many infectious diseases, including smallpox, measle, and poliovirus.
The recently published paper also concluded that the new paradigm of evolving herd immunity during a pandemic cannot be disregarded. It also noted that "Crosstalk among microbiota, metabolism and environmental factors is critical for developing a competent immune system, which is a prerequisite for evolving herd immunity against any contagious infections."
The researchers also explained that the prevalence of heterologous immunity due to mass vaccination initiatives at the grassroots level may provide protection against the novel Coronavirus. The comparisons between COVID-19 and human poliovirus type 3 have offered great insights into the concept of heterologous immunity and, this can be an alternative providing prophylactic intervention against both diseases.