People who received two doses of Pfizer's COVID-19 vaccine might get the same increase in immunity from a Johnson & Johnson booster dose as one from Pfizer, according to a small study published Dec. 5 in the preprint server MedRxiv.
A research team from Beth Israel Deaconess Medical Center in Boston examined 65 people who had received two doses of Pfizer's COVID-19 vaccine. The researchers administered boosters six months after the second dose, giving 24 people a Pfizer booster and 41 a Johnson & Johnson booster.
Both boosters increased the number of T-cells within the body, which are essential for long-lasting immunity and preventing progression to severe disease. However, people who received the Johnson & Johnson booster experienced a T-cell increase twice as high as those who received Pfizer's.
Antibody levels increased after two weeks among people who received a Pfizer booster, then decreased by a quarter by four weeks. People who received Johnson & Johnson's booster saw their antibody levels double between the second and fourth weeks. By the fourth week, the antibody levels produced by Pfizer's booster were still about 50 percent higher than Johnson & Johnson’s. Both levels were significantly above the threshold experts believe is necessary for strong protection, according to The New York Times.
The study, which has yet to be peer reviewed, was funded in part by Johnson & Johnson.