Among people who were previously infected with the coronavirus, a third dose of an mRNA vaccine from Pfizer PFE.N/BioNTech 22UAy.DE or Moderna MRNA.O may not boost their protection against the Omicron variant of the virus, according to new data.
Researchers studied nearly 130,000 people tested for COVID in Connecticut from November 2021 through January 2022, including 10,676 with Omicron infections.
Roughly 6% to 8% had been infected with previous versions of the coronavirus, according to a report posted on medRxiv ahead of peer review.
Two doses of an mRNA vaccine did help protect against Omicron among people with prior infections, but “we did not detect an additional benefit of receiving a third booster dose among this population,” said Margaret Lind of Yale University.
A separate study from Canada, also posted on medRxiv ahead of peer review, similarly found that more than two vaccine doses “may be of marginal incremental value” for protecting previously-infected individuals against Omicron.
The message, Lind said, “should be that (1) people should get two doses of mRNA vaccine regardless of if they have had a prior infection or not, that (2) people without prior infections should get a booster dose and that (3) people with prior infections should consider a booster dose, especially if they are in a high risk group for life threatening complications, but recognize that it may not provide significant additional protection against infection above two doses.”