Pharmaceutical company Johnson & Johnson on Tuesday said that a booster shot of its single-dose Covid-19 vaccine provided 94% protection against symptomatic infection.

The company released data from two studies that assessed the safety of its Janssen vaccine and the immune response it induced.

“Our single-shot vaccine generates strong immune responses and long-lasting immune memory,” a statement by the company quotes Mathai Mammen, head of Janssen Research and Development at the firm, as saying. “And, when a booster of the Johnson & Johnson COVID-19 vaccine is given, the strength of protection against COVID-19 further increases.”

The company said that a single dose of the vaccine showed an efficacy of 79% in preventing coronavirus infections and 81% in preventing hospitalisations. “There was no evidence of reduced effectiveness over the study duration, including when the Delta variant became dominant in the U.S.,” the company’s statement said.

The study on the single-shot vaccine was conducted from March to late July.

The study on booster doses showed that a second shot administered after 56 days provided 100% protection against severe Covid-19, and 94% against moderate symptomatic infection. It also showed that after the booster dose, antibody levels increased to four to six times higher than what was observed after the first shot.

Johnson & Johnson said that it has provided the data to the United States’ Food and Drug Administration, adding that it will also submit the data to other regulators, technical advisory groups on vaccines worldwide and the World Health Organization.

The Janssen vaccine has been approved for use in the US and across Europe, AP reported. The company is also reportedly planning to share at least 200 million (20 crore) doses with the United Nations-backed Covax initiative aimed at providing vaccines to poor countries.

India granted emergency use authorisation to Johnson & Johnson’s vaccine on August 7. The government’s announcement came just two days after the company applied for approval of its vaccine in India.