As Virus Data Mounts, the J.&J. Vaccine Holds Its Own

Once dismissed as less effective, the vaccine now seems to be preventing infections and illness about as well as the two mRNA options.

Approximately 17 million Americans received the Johnson & Johnson Covid vaccine, only to discover later that it was the least protective available in the country. According to new data, the vaccine now prevents infections, hospitalizations, and deaths at least as well as the Pfizer-BioNTech and Moderna vaccines.

Some experts aren’t convinced that the vaccine has proven itself, and the reasons aren’t clear. However, the accumulating data offer considerable reassurance to vaccine recipients, and if confirmed, they may have broad implications for its deployment in various parts of the world.

The most practical option in Africa, for example, is to distribute single-dose vaccines that can be refrigerated for months.

Johnson & Johnson has temporarily shut down the only plant producing usable vaccine batches. Aspen Pharmacare, based in South Africa, is preparing to supply large quantities across the continent. Only 13 percent of Africans are fully vaccinated, and only 1 percent have received a booster shot.

“For Africa, where we need vaccines quickly, the single dose is exciting,” said Linda Gail-Bekker, director of the Desmond Tutu HIV Center at the University of Cape Town, who has studied the vaccine’s effectiveness there.

The Johnson & Johnson vaccine was marketed as an attractive option for communities with limited access to health care, including some in the United States. There have been bumps along the way.

Single-dose vaccines produced a weaker initial immune response, and more people with the single-dose vaccine had breakthrough infections than those who had two doses of the mRNA vaccines Pfizer or Moderna.

Health officials in the United States and South Africa halted the J.&J. vaccine distribution as they investigated reports of a rare blood-clotting disorder in women. While both countries resumed the rollouts shortly after, the vaccine’s reputation never fully recovered.

According to some experts, the idea that the vaccine is inferior has become outdated. Recent data suggest that it has more than held its own against its competitors.

It has been our understanding that J.&J. has been downgraded in people’s minds,” Gail-Bekker said. Although it is a single-dose vaccine, “it punches above its weight.”

C.D.C. data showed that until last June, immunization with Moderna resulted in the lowest rates of breakthrough infections; Johnson & Johnson had the highest rates, with Pfizer-BioNTech in the middle.

In the summer, the gaps — especially between Johnson & Johnson and Pfizer — began to close. As of now, all vaccines seem to be performing similarly against Coronavirus infections; Johnson & Johnson seems to be doing slightly better.

As of Jan. 22, the latest data available, unvaccinated people were 3.2 times as likely to become infected as those who received the single-dose Johnson & Johnson vaccine; they were 2.8 times as likely to become infected as those who received two doses of the Moderna vaccine and 2.4 times as likely as those who received two doses of Pfizer-BioNTech vaccine. Compared to the two alternatives, the Johnson & Johnson vaccine appeared to be somewhat more protective against infection.

It appears that all vaccines were roughly equally effective against infection among Americans who received booster doses. Johnson & Johnson’s previous level of protection was not greatly improved by a booster shot (although the data do not indicate which type of booster shot was given).

The C.D.C. collected data from 29 jurisdictions, representing 67 percent of the population.

“These data add to the growing body of evidence that the Johnson & Johnson Covid-19 vaccine protects against breakthrough infections and hospitalizations,” the company said.

According to the findings, J.&J.’s vaccine deserves a closer look, said Doctor, an expert in vaccine development at Fred Hutchinson Cancer Research Center.

The vaccine platform may have some unexpected characteristics that we hadn’t anticipated, he said. We should spend more time understanding the data, since it is interesting and provocative.

According to Doctor, the results are in line with his experience in H.I.V. research with the adenovirus that forms the backbone of the Johnson & Johnson vaccine. “It has a much longer durability than almost any other platform we’ve ever worked with,” he said.

With each passing month, scientists are only beginning to understand why the vaccine’s profile is improving.

After vaccination, antibody levels skyrocket for a few weeks, but then rapidly decline. According to some research, the J.&J. vaccine may produce antibodies that decline more slowly than those produced by other vaccines. A biological phenomenon called affinity maturation may cause those antibodies to become more sophisticated over time.

Some researchers suggest the vaccine offered a more robust defense against the Omicron variant responsible for the recent increase in infections. The vaccine also trains other parts of the immune system at least as well as the other two.

It is not universally agreed that Johnson & Johnson’s vaccine is catching up. According to Natalie Dean, a biostatistician at Emory University, it may only appear effective now because many recipients had breakthrough infections early on. According to her, they may have a different immune profile.

Johnson & Johnson vaccine recipients who did not get a booster now have a lower infection rate. Even so, Doctor noted that the death rate is slightly higher than that among those who received the Pfizer-BioNTech and Moderna vaccines.

Although the differences are small, they disappeared among those who received booster shots. The C.D.C.’s statistics on deaths only run through Jan. 1, and the Johnson & Johnson vaccine’s edge may not become apparent until February or March, according to Dan Barouch, a virologist at Beth Israel Deaconess Medical Center in Boston who collaborated with Johnson & Johnson in its development.

It is common for deaths to lag infections by weeks or months, “since many deaths occur after prolonged hospital stays,” he explained.

As a result, Doctor would prefer to see data with information on individual factors, like prior infections and other high-risk conditions, rather than the CDC’s age-adjusted overall figures.

It is a shame that we do not have more direct studies of outcomes among people who received J.&J., she said. In part, that’s because fewer people got the vaccine than mRNA vaccines, but it’s also because we’re relying on other countries to generate data.

The South African government has provided some of that information. Approximately 240,000 health care workers were evaluated in the Sisonke study by Doctor and her colleagues, who administered one dose of the Johnson & Johnson vaccine and two doses.

First, researchers matched the recipients with a control group based on age, sex, risk factors for Covid, socioeconomic status, and prior Covid infection. During the time when the Delta variant was dominant in the country, the vaccine had an effective rate of 67 percent against hospitalization and about 82 percent against death. There was a similar level of protection against the Beta variant.

“The single dose worked very well during the Beta and Delta waves,” said Doctor.

A booster of the same vaccine was offered to the participants when the Omicron variant began circulating in South Africa. More than half of them disagreed.

“The pushback was extraordinary,” Doctor said. At that point, it was perceived that Pfizer-BioNTech and Moderna vaccines were superior. “It seemed like we were offering a very second-rate product,” she said.

In spite of this, the data suggest that two doses of the J.&J. vaccine were as effective as the Pfizer-BioNTech vaccine against hospitalization with the Omicron variant. Researchers presented the findings in Denver last month at the Conference on Retroviruses and Opportunistic Infections.

Experts said that even though the trial only looked at people who received two doses of the Johnson & Johnson vaccine, it suggests it could be an excellent booster for those who received two doses of an mRNA vaccine.

Johnson & Johnson’s mRNA vaccines were recommended over the mRNA vaccines by the C.D.C. in December, citing the risk of rare side effects like blood clots and Guillain-Barré syndrome. Blood clots were found in four cases per million people who received the vaccine; women ages 30 to 39 had the highest incidence, at about 11 per million.

There have also been uncommon side effects associated with mRNA vaccines. Every 100,000 vaccinated males aged 16 to 29 are thought to develop myocarditis, or inflammation of the heart.

It may be possible to determine which combination of vaccines is safest and most effective in the long run, Doctor said. Some vaccines may also benefit from the arrival of new variants, according to her.

“I keep an open mind about what might be the best vaccine regimen in the future,” she says.

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