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After SARS-CoV-2 infection, antibodies protect most healthcare workers from reinfection for up to 6 months, the results of the subject’s first prospective study reveal.
Dr. David Eyre
The main message for healthcare workers is that “if you’ve had COVID, at least in the short term, you’re unlikely to get it again,” David Eyre, lead author, associate professor at the Big Data Institute and infectious disease clinician said Oxford University, Oxford, UK Medscape Medical News.
Eyre and colleagues evaluated the presence of two antibodies against SARS-CoV-2 among 12,541 UK health workers, including approximately 10% who had a history of confirmed polymerase chain reaction (PCR) infection. Of these, 223 that had no antibodies tested positive for PCR for the virus during the 31 weeks of follow-up; two participants who had no antibodies at first tested positive.
The study was published online today at The New England Journal of Medicine.
Dr. Mark Slifka
“It’s great news because there have been so many questions about whether or not it can be protected against reinfection, and this health worker study is really an elegant way to address that question,” said Dr. Mark Slifka. Medscape Medical News when asked to comment on the findings.
Although “there are millions of people in the United States who have become infected with COVID, we don’t know how frequent reinfection is,” said Slifka, a researcher at the Oregon National Primate Research Center and a professor at Oregon Health Sciences University School. of Medicine, Portland, Oregon.
The probability of a positive result of the subsequent PCR test was 1.09 for every 10,000 days of risk among those who had no antibodies, compared with 0.13 for 10,000 days among those who had anti-ear antibodies. .
The researchers also evaluated for the presence of anti-nucleocapsid IgG antibody titers. They found a significant trend to increase the results of PCR-positive tests with increasing antibody levels. Similar to anti-ear antibody findings, 226 of the 11,543 healthcare providers who did not have anti-nucleocapsid IgG antibodies tested positive after PCR; in contrast, two of the 1172 participants who had no antibodies tested positive. Adjusted for age, sex, and calendar time, this finding translates into an incidence rate of 0.11 (0.13 per 10,000 days of risk; 95% CI: 0.03 – 0.45; Pg = .002).
“This is a study that many of us have been trying to do,” said Christopher L. King, MD, professor of pathology and associate professor of medicine at Case Western Reserve University School of Medicine, Cleveland, Ohio.
“We really follow a group like this longitudinally as they have done, with a large population, and see such a big difference: it really confirms our suspicion that those who become infected and develop an antibody response are significantly protected against reinfection.
“The good thing about this study is that it reduces almost threefold in risk if you have recovered from COVID and have antibodies,” said King, who was not involved in the research. “That’s what a lot of us wanted to know.”
Questions remain unanswered
“We don’t know how long this immunity lasts,” King said. He predicted that antibody protection could last from a year to a year and a half. The duration of protection may vary. “We know that some people lose their antibodies pretty quickly and others don’t,” he said.
Slifka said the suggestion “of a substantially reduced risk for at least 6 months … is great news, and the timing couldn’t be better, because we’re rolling out vaccines.”
Interestingly, not all antibody responses are the same. For example, the data indicate that antibody levels after vaccination with Pfizer / BioNTech or Moderna vaccines are higher than the average for people who have had a natural infection, King said. He added that initial data on the developing COVID-19 AstraZeneca vaccine showed lower antibody levels compared to natural immunity.
The Centers for Disease Control and Prevention recommends vaccination for those with a history of infection. “People who have become ill with COVID-19 can still benefit from the vaccine,” the CDC notes on its website Facts About COVID-19 Vaccines. “Due to the serious health risks associated with COVID-19 and the fact that a new infection with COVID-19 is possible, people may be advised to take a vaccine against COVID-19 even if they have been ill with COVID-19 “states the CDC.
The agency also notes that people appear susceptible to reinfection about 90 days after the onset of the infection. However, new evidence from the UK study that people have up to 6 months of immune protection may lead to a change in recommendations, especially at a time when vaccine supply is limited, Slifka said. .
Another unanswered question is why both participants in the antibody study tested positive for reinfection. “There are a lot of things that could have made these people more susceptible,” King said. For example, they may have been highly exposed to SARS-CoV-2 or may have been immunocompromised for another reason.
In addition, the immune response involves more than antibody levels, King noted. Research in rhesus monkeys suggests that T cells play a role, but not as important as antibodies. “What I think protects us from infection are mainly antibodies, although T cells are probably important. Once you get infected, T cells probably play a more important role in terms of whether you put them on. very sick or not, ”he said. dit.
Multiplication + Addition = More protected?
Slifka noted that protection of 90% of the study’s natural immunity is close to the 95% efficacy associated with Pfizer and Moderna vaccines. Even without vaccination, this could mean that a portion of the U.S. population is already protected from future infections.
In addition, the CDC estimates that there are approximately 7.7 cases of COVID-19 for each case reported.
As of Sept. 30, the CDC reported that there were 6,891,764 confirmed cases. The agency estimated that approximately 53 million people in the United States have been infected. Recent data from the Coronavirus Resource Center at Johns Hopkins University School of Medicine indicate that there were 18.2 million cases in the United States on December 22nd. If that account is multiplied by 7.7, the total number protected could reach 140 million, Slifka said.
“This could really be a boost in terms of overthrowing this pandemic in the next two months,” Slifka said.
“Now, if we modified the current recommendations and briefly postponed vaccination of people with confirmed cases of COVID-19 until later, we could start achieving herd immunity fairly quickly,” he added.
Implications for real life
“There is no 100% protection, even against the infection itself. Therefore, when it comes to a person with possible exposure to COVID-19, proper precautions must be followed,” Slifka said.
Still, he said, “This is great news for frontline people who are wondering whether or not they would have protection if they had COVID-19 before. And the answer is yes: there is a very good chance they will have protection based in this rather broad study “.
One of the limitations of the study is that the population consisted primarily of healthy adult health workers aged 65 and under. “Additional studies are needed to assess postinfection immunity in other populations, including children, older adults, and people with coexisting conditions, including immunosuppression,” the researchers note.
Eyre plans to continue following the study’s health workers, some of whom have been vaccinated against COVID-19. This ongoing research will allow him and coin researchers to “confirm the protection offered by vaccination and investigate how postvaccine antibody responses vary depending on whether you have had COVID-19 before or not. We also want to understand more about how long post-infection immunity lasts.” . “
Eyre has received grants as a fellow of the Robinson Foundation and a senior fellow of the NIHR Oxford BRC during the conduct of the study. Slifka and King do not report relevant financial relationships.
N Engl J Med. Published online December 23, 2020. Full text
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