A two-dose version of Johnson & Johnson's coronavirus vaccine provides 94% protection against symptomatic infection, the company said Tuesday -- making a two-dose regimen of J&J's Janssen vaccine comparable to a two-dose regimen of Moderna's or Pfizer's.

Plus, the company said, adding a booster dose to a single shot of the vaccine raised immunity even more, and should also protect people strongly against infection.
The company released some details of three studies looking at various aspects of its Janssen vaccine and said that taken together, they showed the vaccine provided long-lasting protection that could be boosted with an extra shot.

"Our large real-world-evidence and Phase 3 studies confirm that the single-shot Johnson & Johnson vaccine provides strong and long-lasting protection against COVID-19-related hospitalizations," Dr. Mathai Mammen, global head of Janssen Research & Development, said in a statement.

"Our single-shot vaccine generates strong immune responses and long-lasting immune memory. And, when a booster of the Johnson & Johnson COVID-19 vaccine is given, the strength of protection against COVID-19 further increases."
Johnson & Johnson's single-dose vaccine was given emergency use authorization by the US Food and Drug Administration on February 27. It has been given to about 14.8 million Americans, according to the US Centers for Disease Control and Prevention.
The company's ongoing Phase 2 trial of a two-dose regimen showed giving two doses 56 days apart provided 100% protection against severe Covid-19 and 94% protection against moderate to severe Covid-19 in the United States. Globally, the two-dose regimen provided 75% protection against moderate-to-severe Covid-19, the company said.