Johnson & Johnson said Wednesday that a second dose of its Covid-19 vaccine was found in a study to generate a strong immune response, justifying a booster shot after eight months.
The Centers for Disease Control and Prevention has said it expects single-dose J&J vaccine recipients would need boosters but has held off on making recommendations as it awaits more data. Wednesday’s findings are expected to inform the U.S. booster strategy set to begin in September, when the U.S. plans to begin offering boosters to people who received messenger-RNA vaccines. Later it is likely to expand the program to include J&J’s viral-vector vaccine.
J&J said researchers found antibody levels increased ninefold among people who received a second dose of its vaccine, compared with one month after they received a first dose. The company didn’t specify exactly when or how many subjects received the second dose, though information posted about the clinical trial in an online government database indicates it was administered six months after the first shot.
J&J said that it will submit data from two studies to a preprint server, meaning that the data haven’t been peer-reviewed or published in a scientific journal.
The company said researchers observed significant increases in antibody responses in participants between ages 18 and 55 and in those 65 and older who received a lower booster dose.
