Protection against Covid-19 from an mRNA vaccine – either the Moderna or Pfizer/BioNTech shots – may last longer after the booster dose than after the original two-shot regimen, researchers speculated based on the results of a small new study.
They measured vaccine responses before and after the boosters in 33 healthy middle-aged adults who had received their second doses an average of nine months earlier. Before the boosters, their antibody levels had decreased about 10-fold from levels early after their second dose. By 6 to 10 days after the booster, their antibody levels had climbed 25-fold and were five times higher than after two doses of the vaccine, according to a report posted on Sunday on medRxiv ahead of peer review.
In the volunteers who had Covid-19 before being vaccinated, antibody levels after the booster were 50-fold higher than after their infections.
“Because these antibody levels are so robust, the booster could potentially give us protection for a longer duration than what we saw for two doses of the vaccine,” study coauthor Alexis Demonbreun of Northwestern University Feinberg School of Medicine in Chicago, said in a statement. [Reuters]