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After infection with SARS-CoV-2, antibodies protect most health professionals against reinfection for up to 6 months, according to the results of the patient’s first prospective study.
Dr. David Eyre
The main message to health professionals is, “If you’ve had COVID, at least in the short term, you’re unlikely to get it again,” David Eyre, senior author, associate professor at the Big Data Institute and infectious disease physician at told the University of Oxford, Oxford, United Kingdom Medscape Medical News.
Eyre and colleagues assessed the presence of two antibodies to SARS-CoV-2 among 12,541 healthcare workers in the United Kingdom, including about 10% with a history of polymerase chain reaction (PCR) confirmed infection. Of those, 223 who had no antibodies tested positive for PCR for the virus at 31 weeks of follow-up; two participants who had no antibodies at baseline tested positive.
The study was published online today in The New England Journal of Medicine.
Dr. Mark Slifka
“It’s great news because there are so many questions about whether or not to protect against reinfection, and this research on health professionals is a really elegant way to address that question,” said Mark Slifka, PhD. Medscape Medical News when asked to comment on the findings.
Although “there are millions of people in the US who are infected with COVID, we don’t know how common re-infection is,” said Slifka, a researcher at the Oregon National Primate Research Center and a professor at the Oregon Health Sciences University School of Medicine. , Portland, Oregon.
The likelihood of another positive PCR test result was 1.09 per 10,000 days at risk among those without antibodies, compared to 0.13 per 10,000 days among those with anti-spike antibodies.
The researchers also assessed the presence of anti-nucleocapsid IgG antibody titers. They found a significant trend for increasing PCR positive test results with increasing antibody levels. Similar to the anti-spike antibody findings, 226 of the 11,543 health care providers who did not have anti-nucleocapsid IgG antibodies subsequently tested positive for PCR; In contrast, two of the 1,172 participants who had no antibodies tested positive. Adjusted for age, gender, and calendar time, this finding translates into an incidence rate of 0.11 (0.13 per 10,000 days at risk; 95% CI, 0.03-0.45; P. = .002).
“This is a study that some of us have tried to do,” said Christopher L. King, MD, PhD, professor of pathology and associate professor of medicine at Case Western Reserve University School of Medicine, Cleveland, Ohio.
“To 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 get infected and develop an antibody response are significantly protected against reinfection.
“The great thing about this study is that the risk is nearly ten times higher if you have recovered from COVID and have antibodies,” said King, who was not involved in the study. “That’s what many of us wanted to know.”
There remain unanswered questions
“We don’t know how long this immunity will last,” said King. He predicted that antibody protection could last from a year to a year and a half. The duration of protection can vary. “We know that some people lose their antibodies quite quickly and some 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 as we roll out the vaccines.”
Interestingly, not all antibody responses are the same. For example, data indicates that antibody levels after immunization with the Pfizer / BioNTech or Moderna vaccines are, on average, higher than those of people who have had a natural infection, King said. He added that initial data on the AstraZeneca COVID-19 vaccine under development showed lower antibody levels compared to natural immunity.
The Centers for Disease Control and Prevention recommends immunization for people with a history of infection. “People who have become ill with COVID-19 may still benefit from vaccination,” the CDC notes on its website Facts About COVID-19 Vaccines. “Because of the serious health risks associated with COVID-19 and the fact that re-infection with COVID-19 is possible, people may be advised to receive a COVID-19 vaccine even if they have previously had COVID-19,” states the CDC.
The agency also notes that about 90 days after the infection starts, people seem to become prone to reinfection. However, the new evidence from the UK study that individuals have immune protection for up to 6 months could lead to an adjustment in the recommendations, especially at a time when vaccine supplies are limited, Slifka said.
Another unanswered question is why the two study participants with antibodies then tested positive for reinfection. “There are many things that could have made these people more susceptible,” said King. For example, they may have been heavily exposed to SARS-CoV-2 or immunocompromised for some other reason.
In addition, the immune response spans more than antibody levels, King noted. Research in rhesus monkeys suggests that T cells play a role, but not as prominently as antibodies. “What I think protects us from infection is primarily the antibodies, although the T cells are probably important. Once you are infected, the T cells probably play a more important role in whether you get very sick or not, ”he said.
Multiplication + addition = more protected?
The 90% natural immunity protection in the study approaches the 95% efficacy associated with the Pfizer and Moderna vaccines, Slifka noted. Even without immunization, this could mean that some of the US population is already protected from future infections.
In addition, the CDC estimates that there are approximately 7.7 cases of COVID-19 for each reported case.
On September 30, the CDC reported that there were 6,891,764 confirmed cases. The agency estimated that a total of about 53 million people in the United States are infected. More recent figures from the Coronavirus Resource Center at Johns Hopkins University School of Medicine indicate that there were 18.2 million cases in the United States as of December 22. If that number is multiplied by 7.7, the total number protected could approach 140 million, Slifka said.
“That could really be a boost in stopping this pandemic in the coming months,” said Slifka.
“If we changed current recommendations now and briefly delayed vaccination of people with confirmed cases of COVID-19 until later, we could achieve herd immunity quite quickly,” he added.
Real-life implications
“There is no such thing as 100% protection, even against the infection itself. So if you are dealing with someone who may have been exposed to COVID-19, you still need to take proper precautions,” said Slifka.
Nonetheless, he said, “This is great news for those on the front lines who are wondering whether or not they would have any protection if they had previously had COVID-19. And the answer is yes – chances are they would have protection based on on this fairly extensive study. “
A limitation of the study is that the population consisted mainly of healthy adult health workers aged 65 or younger. “Further studies are needed to assess post-infection immunity in other populations, including children, older adults, and individuals with coexisting conditions, including immunosuppression,” note the researchers.
Eyre plans to continue to monitor the health workers in the study, some of whom have been vaccinated against COVID-19. This ongoing research will enable him and fellow players to “confirm the protection afforded by vaccination and to examine how the response of antibodies after vaccination varies depending on whether you have had COVID-19 before or not. We also want to know more about how. long immunity after infection. “
Eyre has received fellowships as a Robinson Foundation Fellow and NIHR Oxford BRC senior fellow during the course of the study. Slifka and King do not report any relevant financial relationships.
N Engl J Med. Published online December 23, 2020. Full text
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