A single shot of Johnson & Johnson’s Covid-19 vaccine is effective at keeping people out of the hospital and dying from the illness, the company reported Friday.
Johnson & Johnson, which made the vaccine in partnership with Janssen Pharmaceuticals, is poised to ask the Food and Drug Administration for emergency use authorization as early as next week. If ultimately authorized, it would be the third Covid-19 vaccine available in the U.S., along with Pfizer-BioNTech and Moderna.
Full coverage of the coronavirus outbreak
Johnson & Johnson’s phase 3 trial results found that in the U.S., the vaccine was 72 percent effective in preventing moderate to severe disease. Moderate illness included symptoms such as low oxygen levels, shortness of breath or deep vein thrombosis, while more severe outcomes include hospitalization and death.
When researchers looked just at the shot’s effect on severe disease, it was shown to be 85 percent effective.
This interim analysis focused on 468 cases of symptomatic Covid-19, though the overall research included more than 44,000 participants in the U.S., South Africa, and several Latin American countries.
Efficacy for both moderate and severe illness varied widely by region. While the U.S. data showed 72 percent effectiveness, that percentage fell to 66 percent globally. And in South Africa, where a worrisome variant is the predominant strain, the effectiveness fell to 57 percent.
Still, “not a single person who got vaccinated, and had illness after four weeks, ended up in the hospital,” Dr. Mathai Mammen, global head of pharmaceutical research and development at Johnson & Johnson, told NBC News. This “leads me to believe that this vaccine will stop this pandemic.”
In other words, adding the Johnson & Johnson product to the vaccine toolbox may serve to transform Covid-19 into more of an outpatient illness.
“We have a vaccine that does this critical function of really keeping people out of the hospital,” said Dr. Matt Hepburn, Operation Warp Speed’s Covid-19 response vaccine lead, during a call with reporters Friday.
Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, agreed.
“The most important thing,” Fauci said on the media call, “is to keep people out of the hospital and prevent them from getting severe illness.”
“If you can prevent severe disease in a high percentage of individuals, that will alleviate so much of the stress,” on the health care system, Fauci said.
No major side effects from the vaccine were reported, including severe allergic reactions, such as anaphylaxis, Mammen said.
“What this study showed was superb efficacy against severe disease, hospitalization and death,” said Dr. Greg Poland, director of the Mayo Clinic’s Vaccine Research Group in Rochester, Minnesota. Poland was not involved in the Johnson & Johnson vaccine trials.
Still, the vaccine’s lower efficacy against the South Africa variant, known as B.1.351, is concerning. The strain appears to pose more of a threat to current Covid-19 vaccines than other variants, such as the U.K. variant.
However, Mammen said during the Friday briefing that 28 days after receiving the Janssen shot, no participants in South Africa were hospitalized and none who had been vaccinated died.
“That to us is one of the most exciting results in the test today,” Mammen said.
Those results could be significant for the U.S., as well. The first cases of the South African variant were reported in South Carolina Thursday. On Friday, the director for the Centers for Disease Control and Prevention told TODAY that the B.1.351 variant â€” which is thought to be more contagious but doesnâ€™t cause more severe illness â€” has likely already reached the point of community spread in the U.S.
Moderna said this week that its vaccine appears to be less effective against the South Africa variant, and a Pfizer study also suggested a less robust response. Thursday, biotech company Novavax said that early results from its trials in South Africa also showed a lower effectiveness against the strain.
“With one of the more worrisome variants on the planet, we were still able to show that more often than not, we were able to prevent moderate to severe infection,” said Dr. Buddy Creech, an infectious disease expert, as well as a principal investigator of one of the Johnson & Johnson Covid-19 vaccine trials at Vanderbilt University Medical Center in Nashville.
Download the NBC News app for full coverage of the coronavirus outbreak
People with underlying health conditions such as type 2 diabetes and high blood pressure are at higher risk for severe Covid-19 complications.
“To be able to take that high risk group, and be able to see that none of them ended up in the hospital if they got Covid â€” that’s impressive,” Creech said.
Overall, Johnson & Johnsonâ€™s results are not as strong as those from Pfizer and Moderna, which each had exceptionally high levels of efficacy. Those vaccines have been shown to be about 95 percent effective against symptomatic Covid-19, when given in two shots about a month apart.
“Anytime we know we’re going to see results from our clinical trials, we hold our breath,” Creech said. “If you were to tell me nine months ago that we were going to have a vaccine with over 60 percent efficacy, I would have thought, goodness, that’s better than influenza most years.” Indeed, the flu shot that was administered during the 2019-2020 flu season turned out to be just 45 percent effective.
Unlike Pfizer’s and Moderna’s vaccines â€” which require two doses about a month apart â€” the Johnson & Johnson vaccine can be administered fully in one dose and only requires basic refrigeration for storage. The Pfizer and Moderna vaccines both work using messenger RNA, or mRNA, to teach the immune system how to recognize and fight off the coronavirus. Johnson & Johnson’s vaccine uses a different approach, transporting these instructions into the body using an inactivated adenovirus, a type of virus that causes the common cold.
Two questions remain unanswered: Can the shot stop transmission of Covid-19 from person to person? And would adding a booster further boost overall efficacy?
Research into both of those questions is ongoing at Johnson & Johnson. The company said it should be able to provide data on transmission in the coming months.
The FDA could act on an emergency use authorization by the end of February. Johnson & Johnson expects to supply 100 million doses to the U.S. by June.
Follow NBC HEALTH on Twitter & Facebook.