As vaccine makers set their sights on boosters, new studies unveiled on Wednesday from Johnson & Johnson and Pfizer-BioNTech demonstrated that extra shots can dramatically raise antibodies against the coronavirus.
The companies said they were submitting the new data to the Food and Drug Administration for evaluation, and Pfizer has formally asked the agency to authorize a booster shot. The Biden administration said last week that it wants to provide booster shots for all Americans eight months after vaccination.
The Johnson & Johnson one-shot vaccine was absent from the government’s 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 shot, which showed a 72 percent efficacy against infection in its U.S. clinical trial. That study was done before the Delta variant became widespread. But in another study released earlier this month, South African researchers found that the vaccine was up to 95 percent effective against death from Delta, and reduced the risk of hospitalization by 71 percent.
In its new study, Johnson & Johnson tracked 17 volunteers from last year’s clinical trial. When given a booster shot at six months, their antibodies against the coronavirus jumped nine times as high as after the first dose. The data has not yet been published in a scientific journal.
On Wednesday, Pfizer and BioNTech released new data from 306 people showing that a third dose given five to eight months after the second caused a strong immune response. The level of antibodies against the coronavirus in the volunteers more than tripled, the companies reported.
The side effects of a third injection were about the same as after the initial two doses, the companies said. The underlying data was not included in the news release, nor were the dates or location of the study specified. The companies said they were preparing a scientific publication describing the research.
Pfizer and BioNTech said they were now applying to the F.D.A. for supplemental approval of a coronavirus vaccine booster shot for those aged 16 and up, and will submit all their supporting data by the end of this week.
The news of the booster application came two days after the F.D.A. fully approved the companies’ two-dose vaccine for those 16 and older, making it the first to move beyond emergency use status.
Because booster shots from different companies have not been tested in a head-to-head comparison, it’s not possible to determine which one provides the biggest boost.
It’s also hard to say if these big jumps in antibodies will translate into a highly effective booster shot.
A number of studies have suggested 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 a 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.
The new data from Johnson & Johnson may lay to rest some early concerns about whether more than one dose of the vaccine could be effective. The Johnson & Johnson vaccine uses an adenovirus to deliver coronavirus genes into cells. When the company launched its trials, some experts wondered if people would make antibodies against the adenoviruses, which might render a booster useless.
“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: A six-month pause gives the immune system time to develop a more mature response to the coronavirus.
Only eight percent of vaccinated Americans — or about 14 million people — have received a Johnson & Johnson vaccine, according to the Centers for Disease Control. 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.
It remains to be seen how long the high antibody levels produced by boosters 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.