May 2021, a man receives a Johnson & Johnson Covid-19 vaccination at a pop-up vaccination center on the beach in South Beach, Florida.

Eva Marie Uzcategui | AFP | Getty Images

Johnson & Johnson said Wednesday that a booster of its Covid-19 vaccine produced promising immunity in early clinical trials – although information provided by the company in a press release contained some details.

J & J’s vaccine only requires one dose and recipients are considered fully vaccinated two weeks after receiving the vaccination. The company said Wednesday that J&J recipients who received a booster dose of the shot produced virus-fighting antibodies “nine times higher” than those seen four weeks after a single dose.

Increases in antibody responses were seen in vaccine study participants aged between 18 and 55 years, the company said, and in those aged 65 and over who received a lower dose of the booster.

According to the company, the results are based on two phase 1/2 studies.

“We found that a single shot of our COVID-19 vaccine produces strong and robust immune responses that are sustained and sustained for eight months,” said Dr. Mathai Mammen, head of research and development at J & J’s Janssen vaccines division, in a statement.

“With this new data, we also see that a booster dose of the Johnson & Johnson COVID-19 vaccine further increases antibody responses in subjects who previously received our vaccine,” he added.

While the new data looks promising, the company’s press release didn’t mention the potential impact of the booster shots on the Delta variant or safety.

When asked for data on Delta, J&J referred CNBC to a report in July that showed that a single dose of the vaccine elicited a promising immune response to the variant.

It also begs the question of why J&J recipients need booster shots – especially after the July report showed that a single shot of the vaccine provides at least eight months of immunity and appears to offer adequate protection against the rapidly spreading Delta variant.

Certainly the Centers for Disease Control and Prevention have said that J&J recipients are likely to need a booster dose, but added that there is currently insufficient data to support a formal recommendation.

The company announced on Wednesday that it is working with the Food and Drug Administration and other health authorities on booster shots.

J&J did not immediately respond to additional questions from CNBC on these matters.

The new dates come less than a week after J&J announced that Alex Gorsky is stepping down as CEO. Gorsky, 61, who was Chairman and CEO for nine years, will become Executive Chairman.