People were immune to Covid-19 before it existed: Study

Some degree of immune reactivity against SARS-CoV-2 already pre-existed in the general population, according to a paper published in Nature Reviews Immunology.

Earlier in May, another study by researchers Alba Grifoni and others, also detected reactivity in 50 percent of donor blood samples obtained in the United States between 2015 and 2018.

These studies, therefore, suggest that even before coronavirus-causing SARS-CoV-2 appeared in the human population, some people had grown immune to it.

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Although the recent paper by German researchers Alessandro Sette and Shane Crotty, titled, “Pre-existing immunity to SARS-CoV-2: The knowns and unknowns”, does not conclude the reason for the immunity, it suggests that it might be due to immunity to other coronaviruses in the past.

The researchers note that the detection of the immunity prevalence has implications for Covid-19 disease severity, herd immunity and vaccine development, which still wait to be addressed with actual data.

Founding director of Yale University's Yale-Griffin Prevention Research Center, Dr David L Katz, told CNN in an interview that it is excellent news at the population level.

“We have had indications for this from a long time that many people may not be prone to get this particular virus at all because they have partial native resistance likely due to prior coronavirus exposures,” he said.

Stressing that both the US research paper issued under Cell journal as well as the German research paper, published under the Immunology section of ‘prestigious’ journal Nature, have reached the same conclusion, Katz told the publication that although the ‘percentage side’ is a bit unclear, both the papers point to ‘big numbers’.

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Referring to the papers, he added, “It said the same thing — 40 to 60 percent people without exposure to this particular virus had essentially developed an immune system defence force that was predisposed to react to this virus as if it had seen it before.”

Answering if he thinks a significant amount of population is partly resistant to Covid-19, the preventive medicine specialist said, “My impression is that there has long been evidence that that’s true.”

Citing the example of the Diamond Princess ship which saw a major Covid-19 outbreak, he suggested the presence of “pre-existing immunity” as only a small percentage of the passengers got infected.

READ: Coronavirus-striken Diamond Princess leaves Yokohama

Reviewing the findings of the research papers and its impact on the Covid-19 vaccination efforts, Katz pointed that the studies reveal various aspects of the SARS-CoV-2 our immune system can react to which can be used to trigger a reaction using proteins from different coronaviruses.

“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. 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,” he said in the interview.