At first glance, the results reported on Friday from the long-awaited trial of Johnson & Johnson’s coronavirus vaccine might have seemed disappointing. Its overall efficacy — the ability to prevent moderate and severe disease — was reported at 72 percent in the United States, 66 percent in Latin American countries and 57 percent in South Africa.
Those figures appear far below the high bar set by Pfizer-BioNTech and Moderna, the first two vaccines authorized for emergency use in the United States, which reported overall efficacy from 94 to 95 percent.
Dr. Anthony S. Fauci, the nation’s leading infectious disease expert and now the lead medical adviser to President Biden on the coronavirus pandemic, acknowledged the striking difference at a briefing on Friday.
“If you woke up and you say, ‘Well, go to the door on the left and you get 94 or 95 percent, go to the door on the right and you get 72 percent,’ which door do you want to go to?” he asked.
But Dr. Fauci said that the more crucial measure was the ability to prevent severe disease, which translates to keeping people out of the hospital and preventing deaths. And that result, for Johnson & Johnson, was 85 percent in all of the countries where it was tested, including South Africa, where a rapidly spreading variant of the virus had shown some ability to elude vaccines.
More important than preventing “some aches and a sore throat,” Dr. Fauci said, is to fend off severe disease, especially in people with underlying conditions and in older adults, who are more likely to become seriously ill and to die from Covid-19.
“If you can prevent severe disease in a high percentage of individuals, that will alleviate so much of the stress in human suffering and death in this epidemic that we’re seeing, particularly now,” Dr. Fauci said, “as we well know, over the last several weeks, our health care system has been stressed by the number of people that require hospitalization, as well as intensive care.”
Dr. Francis Collins, director of the National Institutes of Health, compared the ability to prevent severe disease to the effects of flu shots, which do not always prevent influenza entirely but can make it less severe.
“The same thing seems to be applying here, in a circumstance where this variant is clearly making it a little tougher to get the most vigorous response that you would want to have,” Dr. Collins said. “But still, for severe disease, it’s looking really good.”
The Moderna vaccine also showed high efficacy, 100 percent, against severe disease. The Pfizer-BioNTech one appeared to as well, but the overall number of severe cases in the study was too small to be sure.
But researchers warn that trying to compare effectiveness between new studies and earlier ones may be misleading, because the virus is evolving quickly and to some extent the trials have studied different pathogens.
A participant in the Johnson & Johnson vaccine trial in Cape Town, South Africa, last month.Credit…Joao Silva/The New York Times
“You have to recognize that Pfizer and Moderna had an advantage,” Dr. William Schaffner, an infectious disease expert at Vanderbilt University, said in an interview. “They did their clinical trials before the variant strains became very apparent. Johnson & Johnson was testing its vaccine not only against the standard strain but they had the variants.”
The best way to stop the spread of mutants and to prevent more new ones from emerging is to vaccinate as many people as quickly as possible, Dr. Fauci and other researchers say. Viruses cannot mutate unless they are replicating, and they cannot replicate unless they can get into cells. Keeping them out by immunizing people can shut down the process.
In addition to the Pfizer-BioNTech and Moderna vaccines already in use in the United States, three more may soon become available: those made by Novavax, Johnson & Johnson and AstraZeneca. AstraZeneca’s vaccine has already been authorized in Britain and other countries.
Globally, the Johnson & Johnson vaccine is expected to play an important role, especially in low and middle-income countries, because it works after just one shot, is relatively inexpensive and is easier to store and distribute than the vaccines made by Pfizer-BioNTech and Moderna since it does not share their stringent requirements for freezing and refrigerating.
People waiting to be vaccinated may wonder if they will be able to pick and choose among vaccines, and if they should hold out and wait until the one that looks best to them becomes available.
Dr. Paul Offit, a vaccine expert at Children’s Hospital of Philadelphia, told CNN that if there was an abundant supply of the Pfizer-BioNTech and Moderna vaccines, they would be his first choices because of their higher overall efficacy.
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But for now, there is not enough of those vaccines.
If he could not get either the Pfizer-BioNTech vaccine or the Moderna one, he would take the Johnson & Johnson shot, Dr. Offit said — as long as the data that the company will be presenting to the Food and Drug Administration looks as good as what the company reported on Friday.
He said Johnson & Johnson’s report of the reduction in severe disease was a powerful selling point.
“That’s what you want,” Dr. Offit said. “You want to stay out of the hospital, and stay out of the morgue.”
He noted that the company was also studying a two-shot regimen, which might raise its efficacy.
People who take the Johnson & Johnson vaccine should be able to safely receive a Pfizer-BioNTech or Moderna vaccine later if a booster shot is needed, he said.
Dr. Schaffner said he had just attended a meeting with other public health experts, and they had asked one another what they would tell their spouses or partners to do if they could get the Johnson & Johnson vaccine tomorrow, or had to wait three weeks for Pfizer-BioNTech’s or Moderna’s.
“All of us said, ‘Get the one tomorrow,’” Dr. Schaffner said. “The virus is bad. You’re risking three more weeks of exposure as opposed to getting protection tomorrow.”
He said Johnson & Johnson’s 85 percent efficacy against severe disease was a bit lower than those reported by Moderna and Pfizer-BioNTech, “but it’s still pretty darn high.”
It is not yet known whether it would be safe to take one type of vaccine now and then another later, Dr. Schaffner said, adding, “We haven’t studied this.”