Two new studies provide encouraging evidence that having COVID-19 may provide some protection against future infections. The researchers found that people who produced antibodies to the coronavirus were much less likely to test positive again for up to six months and maybe more.
The results are auspicious for vaccines, which cause the immune system to produce antibodies – substances that attach to a virus and help it be eliminated.
The researchers found that people with antibodies to natural infections have a “much lower risk … of the same type of protection you would get from an effective vaccine” to counteract the virus again, said Dr. Ned Sharpless, director of the US National Cancer Institute.
“It’s very, very rare” to reinforce yourself, he said.
The institute’s study had nothing to do with cancer – many federal researchers have moved into coronavirus activity due to the pandemic.
Both studies used two types of tests. One is a blood test for antibodies, which can persist for months after infection. The other type of test uses nasal or other tests to detect the virus itself or its fragments, suggesting a current or recent infection.
A study, published Wednesday by the New England Journal of Medicine, involved more than 12,500 health workers at Oxford University hospitals in the United Kingdom. Of the 1,265 who had coronavirus antibodies at first, only two tested positive for active infection in the next six months and none of them developed symptoms.
This contrasts with the 11,364 workers who initially had no antibodies; 223 of them tested positive for the infection in about six months.
The National Cancer Institute study involved more than 3 million people who had antibody tests at two private laboratories in the United States. Only 0.3% of those who initially had antibodies subsequently tested positive for coronavirus, compared to 3% of those who did not have such antibodies.
“It’s very nice” to see that Oxford researchers saw the same reduction in risk – 10 times less likely to have a second infection if antibodies were present, Sharpless said.
His institute’s report was posted on a website scientists are accustomed to sharing research and are being examined at an important medical journal.
The findings are not “a surprise … but it’s really reassuring because it tells people that immunity to the virus is common,” said Joshua Wolf, an infectious disease specialist at St. John’s Children’s Research Hospital. Memphis County, which had no study role.
The antibodies themselves do not provide protection, it could just be a sign that other parts of the immune system, such as T cells, are able to fight off any new exposure to the virus, he said.
“We don’t know how long this immunity is,” Wolf added. Cases of people who have received COVID-19 several times have been confirmed, so “people still need to protect themselves and others by preventing reinfection”.
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