Giving a booster dose of the Johnson & Johnson shot six months after primary vaccination results in a nine-fold antibody increase, according to the company.
A prior study, which has been peer reviewed, found that people vaccinated with the Johnson & Johnson vaccine still had durable immune response at least eight months later, even without a booster.
Collectively, the findings could help inform the US government's recommendations about booster shots for the 14 million people who received the single-shot Johnson & Johnson vaccine.
Boosting after six months, "appears to be safe, and boosts immune responses substantially," said Dr. Dan Barouch, PhD, director of the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center.
Last week, the Biden administration's announced booster doses are likely to be needed 8 months after the last Pfizer or Moderna dose, but the announcement did not include a specific recommendation for those who received Johnson & Johnson.
At the time, CDC director Rochelle Walensky said data on Johnson & Johnson could be expected "in the next few weeks" and that "with those data in hand, we will keep the public informed with a timely plan for J&J booster shots as well."