(AP) – Two new studies provide encouraging evidence that having COVID-19 may provide some protection against future infections. Researchers found that people who made antibodies to the coronavirus were much less likely to retest positive for up to six months and perhaps longer.
The results bode well for vaccines, which trigger the immune system to make antibodies – substances that attach to a virus and help eliminate it.
Researchers found that people with antibodies to natural infections had “a much lower risk … on the order of the same kind of protection you would get from an effective vaccine” of getting the virus again, said Dr. Ned Sharpless, director. from the US National Cancer Institute.
“It’s very, very rare” to get reinfected, he said.
The institute’s study had nothing to do with cancer – many federal researchers have switched to coronavirus because of the pandemic.
Two types of tests were used in both studies. One is a blood test for antibodies, which can linger for many months after infection. The other type of test uses nasal or other samples to detect the virus itself or pieces of it, indicating a current or recent infection.
One study, published Wednesday by the New England Journal of Medicine, involved more than 12,500 health professionals from Oxford University Hospitals in the United Kingdom. Of the 1,265 who initially had antibodies to the coronavirus, only two had positive results on tests to detect active infection in the following six months, and neither developed symptoms.
This contrasts with the 11,364 workers who initially had no antibodies; 223 of them tested positive for infection in the approximately six months that followed.
The National Cancer Institute study involved more than 3 million people who had undergone antibody testing in two private laboratories in the United States. Only 0.3% of those who initially had antibodies later tested positive for the coronavirus, compared to 3% of those who did not have such antibodies.
“It’s very gratifying” to see that the Oxford researchers saw the same risk reduction – 10 times less likely to have a second infection if antibodies were present, Sharpless said.
His institute’s report was posted on a website that scientists use to share research and is currently being reviewed in a major medical journal.
The findings are “no surprise … but it is really reassuring because it tells people that immunity to the virus is common,” said Joshua Wolf, an infectious disease specialist at St. Jude Children’s Research Hospital in Memphis, who is not in any of the both had a role. study.
Antibodies themselves may not provide the protection, they could simply be a sign that other parts of the immune system, such as T cells, are able to fight new exposures to the virus, he said.
“We don’t know how long this immunity is,” added Wolf. Cases where people got COVID-19 more than once have been confirmed, so “people still need to protect themselves and others by preventing reinfection.”
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