When Johnson & Johnson's COVID-19 vaccine was authorized for use in late February, public health officials emphasized that it was just as good as the others. It was less effective, but because it requires only a single shot for full protection and is easier to distribute, it was a top choice for many people.
Since then, the J&J vaccine has been given far less often than the other two authorized vaccines, accounting for one-tenth as many shots as Moderna's vaccine, which is given less often than Pfizer-BioNTech's.
Recently, three pieces of information have come to light making people who got the J&J vaccine wonder whether their shot might be a distant third in other ways, too.
Studies suggest the J&J vaccine may provide somewhat less protection, particularly against the delta variant, which now accounts for more than 80% of COVID-19 cases across the United States. The J&J vaccine has been associated with very rare cases of dangerous blood clots in the brain. And it may be linked to about 100 cases of a neurological condition called Guillain-Barré syndrome.
"Johnson & Johnson is not a bad vaccine – it’s way better than getting nothing," said Dr. Otto Yang, an infectious disease specialist at UCLA Health. "But it’s not as good as other options."
All things considered, it's a lucky position to be in.
The J&J vaccine looks second-class only because the other two vaccines are so good, experts say.
J&J's pivotal large-scale trial showed it was effective against COVID-19, preventing more than 70% of symptomatic infections and about 86% of serious ones. New data the company presented Thursday to a federal advisory committee shows the protection lasts against all variants now circulating for at least eight months.
Pfizer-BioNTech and Moderna, which are based on a technology called mRNA, showed even higher efficacy in their trials, preventing more than 94% of symptomatic cases and nearly all cases of severe COVID-19.
In a meeting Thursday, members of the Advisory Committee on Immunization Practices agreed that all three vaccines' benefits vastly outweigh their risks. The J&J shot, though it has more potential for serious side effects and may be less effective than the others, should continue to be an option for people who would rather have a single-dose vaccine and are aware of those risks, several committee members said.
"We want to maximize our ability to prevent as much disease as we can, while at the same time maximizing the safety of these vaccines," Dr. Matthew Daley, a senior investigator at Kaiser Permanente Colorado in Aurora, said at the meeting.
All the COVID-19 vaccines carry a small risk of an allergic reaction – two to five people per million – and the mRNA vaccines bring a slight risk of myocarditis, a swelling of the heart, particularly in younger men and adolescents, though most of those cases have been mild.
In the real world, all three shots have proven extremely effective. Only 3% of those hospitalized in the United States with COVID-19 have been vaccinated; 97% have not, according to the Centers for Disease Control and Prevention.
Does the J&J vaccine result in more breakthrough infections?
It's not clear, however, whether any of the vaccines account for more breakthrough cases than the others, said Dr. Paul Offit. who directs the Vaccine Education Center at Children's Hospital of Philadelphia.
Offit said he's more concerned about the CDC not producing or releasing that information than he is about the J&J vaccine itself. "The CDC should know that," he said.
Without that information, people who got the J&J vaccine are left wondering whether they are safe.
"I’m wanting to do more things besides all of my outdoor activities but I'm too scared!" said Jill Oliver, a J&J recipient from Boulder, Colorado.
Everyone else in her family received the Pfizer-BioNTech or Moderna vaccine and feels safe, but because Oliver worries she is less protected, she has continued to wear a mask, even at home.
"Comparing vaccines is tricky," Hannah Sally, senior epidemiologist with Informa Pharma Intelligence, a business information provider, said via email. Trials are conducted at different times when different variants predominate.
According to the CDC, nearly 340 million doses of COVID-19 vaccine have been administered across the country since December: 187 million doses of Pfizer-BioNTecn, 137 million doses of Moderna and 13 million doses of J&J.
Does the J&J vaccine bring more side effects and less variant protection?
Several side effects have turned up with the J&J vaccine that don't seem to occur with the other two.
As of July 19, there have been 39 reports of people getting a rare blood clotting condition called thrombosis with thrombocytopenia syndrome, or TTS, most of them within one to two weeks of receiving the J&J vaccine. The condition involves serious blood clots, often in the brain, as well as low levels of platelets, which help blood to clot and can lead to internal bleeding. Most of the cases have been in women in their 30s and 40s.
Also, about 100 people, most of them men over 50, have been diagnosed with Guillain-Barré Syndrome within 42 days after receiving the J&J shot, although a cause-effect relationship has not been proven. Guillain-Barré also has occurred after other vaccines and – at higher rates – in connection with viral infections such as COVID-19. With the condition, the immune system damages nerve cells, causing muscle weakness and sometimes paralysis. Most people fully recover, though cases can be fatal.
Although J&J studies show their vaccine offers continued protection against most of the known variants, a study posted online this week but not yet peer-reviewed suggested it was less effective against the delta variant. Researchers from New York University, who declined to be interviewed, found that blood samples from people who had received the J&J vaccine were less able to neutralize the delta variant than blood from people who received the Pfizer-BioNTech or Moderna shots.
This form of lab testing offers hints of protection but is not as reliable as showing whether the vaccine works in people, experts said.
Plus, although there are fewer antibodies with the J&J vaccine than the others, it's not clear how many is enough to keep people safe from infection, said Dr. Timothy Brewer, a professor of medicine and epidemiology at the University of California, Los Angeles.
In the real world, "as far as I know, J&J still affords protection from serious disease," said Theodora Hatziioannou, a virologist who was not involved in the study but does similar research at The Rockefeller University in New York. "As it stands, the vast majority of hospital admissions due to COVID-19 are due to infections in the unvaccinated population. So (the J&J vaccine) is still worth taking."
Perhaps, she said, the difference in performance is due to the different numbers of shots required.
Two doses are necessary to be fully vaccinated with either Moderna or Pfizer-BioNTech. Research has shown that a single dose of either is not very protective against variants, such as delta.
So far, only one dose of the J&J shot has been recommended, though the company is studying a two-dose regimen as well.
"It is possible that this difference in performance is due to the fact that it is a single shot and that a booster will improve it," Hatziioannou said.
Should people who got the J&J shot get a booster?
Ali Ellebedy, an immunologist at the Washington University School of Medicine in St. Louis, said that if he had gotten the J&J vaccine, he would want a second shot.
"I would get booster immunization if I had had received only one dose of J&J, preferably one of the RNA vaccines," he said. "That booster might not be absolutely needed to protect me from severe disease but basically an extra insurance."
Others are warier of the J&J shots.
Dr. Leana Wen, an emergency physician and former Baltimore health commissioner, said she has encouraged a few of her high-risk patients to follow up their J&J shot with a single dose of either Pfizer-BioNTech or Moderna.
But there is no research to confirm that mixing shots is safe, Wen said. In some people, the risk of serious infection may outweigh any risk of mixing vaccines, she said.
In those who are younger and healthier, Wen recommends measures like social distancing and mask-wearing. She got the J&J vaccine herself and now avoids crowds and wears a mask in public indoor spaces.
Some believe boosters aren't advisable at all until there's more data.
Data published in Europe suggest that side effects such as fever, sore arm and fatigue are higher when people mix vaccines. "There’s no data to say that it would be better to do a booster with an mRNA vaccine," UCLA's Brewer said.
The U.S. government does not recommend booster shots for anyone at the moment.
Offit said he wouldn't suggest a booster yet for J&J recipients because of a lack of information about safety and need. "I'd like to see those data," he said.
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This article originally appeared on USA TODAY: Is Johnson & Johnson one dose COVID vaccine good enough?