WEB DESK, July 22(ABC): Social media users are sharing online articles and misleading claims about the superiority of “natural immunity” compared to vaccine-induced antibody responses based on results of a study published online in June by the New England Journal of Medicine (NEJM).
The study by Harvard researchers found that 26 people infected with BA.1 or BA.2 versions of the Omicron variant after having received two or three COVID-19 vaccine doses had higher virus-neutralizing antibody levels in their blood, on average, than 27 people who received two or three vaccine doses but had no prior or subsequent infection. A single study subject infected without ever having been vaccinated had no detectable neutralizing antibodies at all.
In one article shared and reprinted widely, titled “COVID-19 Jab Does Not Work. Here’s Why”, the authors partly describe the Harvard study and conclude, “Take the jab, if you want, and get the boosters. But don’t be fooled. They will not give you any more protection than what you already have.”
Others on social media have shared the original study in NEJM with comments that also suggest it shows “natural immunity” is superior to that of vaccines. One Twitter user whose post was shared some 3,500 times commented, “Natural Immunity wins again. New England Journal Study: Natural immunity ‘protection was higher than that conferred after the same time had elapsed since receipt of a second dose of vaccine among previously uninfected persons’”.
These posts conflate “natural immunity” from viral infection alone with “hybrid immunity” gained from vaccination followed by infection.
The senior author of the NEJM study, Dr. Dan Barouch, a professor of medicine at Harvard Medical School and director of the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center, told Reuters that he disagrees with interpretations of the study that suggest immunity from infection alone is superior to that provided by vaccines.
“Our paper doesn’t address the question of natural immunity alone,” Barouch said. The study had only one individual who was unvaccinated and infected, “and actually was hospitalized and had a severe disease course including ICU care.” All the other individuals were vaccinated and boosted, he noted.
“Our study looked at vaccinated people who became infected, which is called hybrid immunity,” Barouch said. The intent of the study was to look at relative levels, or “titers,” of neutralizing antibodies against a range of Omicron variants to understand the potential for newer variants to evade immunity in the population.
In people vaccinated then infected, “we found that titers against BA.5 were about three-fold lower than against BA.1, and about 20-fold lower than against the ancestral strain,” Barouch said. The proportions were similar in people who were vaccinated without being infected: antibody titers against BA.5 were 3.3-fold lower than against BA.1, and 21-fold lower than against the ancestral strain.
The study analyzed antibody levels in serum samples from a Beth Israel Deaconess specimen repository, including samples from 27 individuals with no history of COVID or indicators of prior infection, and from 27 individuals with a documented infection during the periods when the Omicron BA.1 or BA.2 variants were circulating in the Boston region.
Among the individuals who had been infected prior to the sample being taken, all but one had been vaccinated prior to the infection: 20 of the 27 had received three doses of an mRNA vaccine – either the Pfizer or Moderna vaccine or a combination of the two. Another four people had received two doses of the Pfizer vaccine, and two people had received either one or two doses of an adenoviral-vector vaccine plus a shot of the Moderna vaccine. The remaining infected individual was unvaccinated.
Among those vaccinated but never infected, all 27 people had received three doses of the Pfizer/BioNTech COVID vaccine.
The serum samples from people who had been infected were taken a median of 29 days after a positive COVID test, although there was a wide range (2-113 days), the study authors note in their report. The most recent samples from people vaccinated but never infected were taken two weeks after their last vaccine shot.
The sample from the sole unvaccinated individual who became severely ill was taken just four days after COVID diagnosis, when it’s likely that antibodies had not yet been produced, Barouch noted in an interview.
The study did find that neutralizing antibody levels in vaccinated individuals — both infected and uninfected — were by far the highest against the original version of the coronavirus, and lower against the BA.1 and BA.2 versions of Omicron. They were lower still against BA.212.1, a BA.2 descendant that is currently declining in the United States, and lowest of all against the BA.4 and BA.5 variants currently predominant in the U.S.
Overall, neutralizing antibody titers against each of the variants were roughly double in those who had been infected after vaccination compared to those vaccinated but never infected. The study did not assess whether the antibody titers seen in either group would protect against future infection or severe illness.
The results show that “infection is acting as a very robust boost in vaccinated people,” Barouch said.
They are also in line with many previous studies of people infected then vaccinated, or vaccinated then infected, that showed hybrid immunity provides the best responses, Barouch said. “We’re not saying natural immunity has no role, in our paper we don’t make any statements about natural immunity at all.”