A new study published in the journal Nature Reviews Immunology reveals that 40% to 60% of people already developed immunity to COVID-19 before the advent of the pandemic. The immune reactivity to the disease pre-existed in people and this means many people will never be sickened with the disease or show any symptoms at all.
The study corresponds with the conclusions of another titled Pre-existing immunity to SARS-CoV-2: The Knowns and Unknowns and published by German researchers Alessandro Sette and Shane Crotty. Both studies said some people developed immunity to the disease because of earlier immunity to other types of coronaviruses in the past.
In May, a different study by Alba Grifoni and other researchers found immune reactivity in 50% of blood samples donated by people in the US from 2015 to 2018.
All the studies point to the fact that some people had developed immunity to COVID-19 before the emergency of the disease, and analysts said the discovery is important to understanding the severity of the disease and developing effective vaccines. Vineet Menachery, a COVID-19 researcher at the University of Texas Medical Branch noted that the spread of coronavirus will soon slow down with or without vaccines due to herd immunity.
According to the founding director of Yale University’s Yale-Griffin Prevention Research Center, Dr. David L. Katz, many people may not fall victim to the pandemic because “they have partial native resistance likely due to prior coronavirus exposures.” He revealed that the percentages reached by all the studies are not clear, but the fact remains that people with native immunity to COVID-19 are in large numbers.
“It said the same thing — 40 to 60 percent people without exposure to this particular virus had essentially developed an immune system defense force that was predisposed to react to this virus as if it had seen it before,” Katz said.
Referring to the incident of the Diamond Princess ship where only a small number of the passengers got infected with the coronavirus, Katz said it is likely as a result of pre-existing herd immunity among the passengers.
With the various studies, Katz said scientists can obtain the proteins of various strands of coronaviruses to create vaccines that will boost natural immunity to the disease.
“The more ways you have of triggering an immune response that’s protective against a particular threat, the more opportunity you have to create an effective vaccine,” he said. “So, even if this isn’t directly related to vaccine development efforts that are ongoing now but I think it’s good news on the vaccine front too.”