In the midst of a delta variant surge, a new study finds that giving a booster dose of the Johnson & Johnson shot six months after primary vaccination results in a nine-fold increase of a crucial antibody response, according to a company press release.

Meanwhile, a prior study found that people vaccinated with the Johnson & Johnson vaccine still had a durable immune response at least eight months later, even without a booster.

Collectively, the findings could help inform the U.S. 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," Dr. Dan Barouch, Ph.D., director of the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center, told ABC News.

The new data shows "a booster dose of the Johnson & Johnson COVID-19 vaccine further increases antibody responses among study participants who had previously received our vaccine,” said Dr. Mathai Mammen, Global Head, Janssen Research & Development, Johnson & Johnson, in prepared remarks.