Second Dose of J. & J. Vaccine Gives Strong Boost, Company Reports

A booster shot of the Johnson & Johnson vaccine dramatically raises the levels of antibodies against the coronavirus, the company reported on Wednesday.

Johnson & Johnson will submit the data to the Food and Drug Administration, which is evaluating similar studies from Pfizer and Moderna. If authorized by the agency, the Biden administration wants to provide booster shots eight months after vaccination.

The Johnson & Johnson vaccine was absent from the government’s initial booster plan, announced last week. But with the new data, the company hopes to be part of the initial distribution of additional shots, which could happen as early as September.

“We look forward to discussing with public health officials a potential strategy for our Johnson & Johnson Covid-19 vaccine, boosting eight months or longer after the primary single-dose vaccination,” Dr. Mathai Mammen, the global head of Janssen Research & Development at Johnson & Johnson, said in a statement.

In February, the F.D.A. gave emergency authorization to Johnson & Johnson for its one-shot vaccine. A clinical trial carried out last fall and winter showed that a single shot had a 72 percent efficacy in preventing symptomatic Covid-19 among U.S. participants. In the trial, none of the vaccinated volunteers were hospitalized or died.

Johnson & Johnson carried out its clinical trial before the Delta variant became widespread, leaving open the question of how well the vaccine worked against the highly contagious form of the virus. But in a study released earlier this month, South African researchers found that a single shot of the Johnson & Johnson vaccine was up to 95 percent effective against death from the Delta variant, and reduced the risk of hospitalization by 71 percent.

In its new study, Johnson & Johnson tracked 17 volunteers from last year’s clinical trial. Six months after vaccination, their level of antibodies had changed little.

That’s different than the pattern seen with the Moderna and Pfizer-BioNTech vaccines. Those shots initially produce higher levels of antibodies, but their levels then drop over several months.

When volunteers in the Johnson & Johnson trial were given a booster shot at six months, their antibodies against the coronavirus jumped nine times higher than after the first dose.

Studies on Moderna and Pfizer-BioNTech vaccines found a comparable jump in antibody levels. Because the three vaccines were not tested in a head-to-head comparison, it’s not possible to determine which one provides the biggest boost.

Johnson & Johnson said that it had submitted a manuscript describing the research to the website Medrxiv. It has not been posted there yet.

A number of studies suggest that higher levels of antibodies provide better protection, especially against the Delta variant. But other parts of the immune system, such as T cells, are also important. So this data cannot give a precise estimate of how effective the booster shot will be against Covid-19.

“It’s too early to guesstimate protection,” said Dr. Dan Barouch, a virologist at Beth Israel Deaconess Medical Center in Boston, who has led some studies for Johnson & Johnson but was not involved in the booster trial.

Aside from antibodies, Johnson & Johnson researchers also found that the booster increased the body’s supply of immune cells that can attack cells infected with the coronavirus. Those results are still being prepared for publication.

The Johnson & Johnson vaccine uses an adenovirus to deliver coronavirus genes into cells. When the company launched its trials, some exerts wondered if people would make antibodies against the adenoviruses, which might render a booster useless. The new findings show that’s not the case.

“Something we previously would have considered to be a major barrier may not be such a huge barrier,” said Lynda Coughlan, a virologist at the University of Maryland School of Medicine, who was not involved in the study.

The Johnson & Johnson vaccine is the only shot in the United States or Europe authorized as a single dose. Since November, the company has been running a clinical trial to look at how much protection people get from two doses, two months apart. That trial is expected to deliver results in the next few weeks.

After the volunteers in that trial received the second dose, their antibody levels rose by a factor of three. The much bigger increase in the new booster study is likely because of the longer wait between doses. The six-month pause gives the immune system time to develop a more mature response to the coronavirus.

This spring, Johnson & Johnson’s vaccine distribution was greatly hampered in the United States by a contractor’s mishandling of its manufacturing at a Maryland factory. Only eight percent of vaccinated Americans — or about 14 million people — have received a Johnson & Johnson vaccine, according to the Centers for Disease Control.

Since then, the U.S. supply of the vaccine has grown. A federal official said that the government had sufficient supplies in reserve to give boosters to everyone who received a first dose of Johnson & Johnson, should it be authorized.

The news of potential Johnson & Johnson boosters for Americans may sting in other countries that are still waiting for first doses of the vaccine. South Africa, for example, has ordered 31 million doses of the vaccine, but only two million people there have received it.

In an interview with CNBC last month, a Johnson & Johnson executive said the company aims to produce 500 million to 600 million doses globally in 2021.

It remains to be seen how long the high antibody levels produced by the booster will last. “We don’t have long-term human studies, but my prediction would be that those responses should be maintained after the boost,” Dr. Coughlan said.

Noah Weiland contributed reporting.