Updated August 25, 2021 at 8:37 AM ET
Johnson & Johnson says it has evidence that people who received its one-shot COVID-19 vaccine could benefit from a booster shot after six months.
The pharmaceutical giant said in a news release Wednesday that when it gave participants in a study a second jab of its coronavirus vaccine after six months, their antibody levels were nine times higher than 28 days after their first dose.
The data suggests that an additional shot might serve as a booster if the vaccine's effectiveness begins to wane.
"We have established that a single shot of our COVID-19 vaccine generates strong and robust immune responses that are durable and persistent through eight months," said Mathai Mammen, global head of Janssen Research & Development, Johnson & Johnson, in a statement.
"With these new data, we also see that a booster dose of the Johnson & Johnson COVID-19 vaccine further increases antibody responses among study participants who had previously received our vaccine," he added.
The data have not yet been published in a scientific journal or reviewed by other researchers.
Johnson & Johnson said it is planning to submit the results of the study to the Food and Drug Administration to help make a case for authorizing a booster for everyone who received the company's vaccine. The company said the study supports a strategy of giving a booster at eight months, even though in the study volunteers were given the second shot at six months.
The Biden administration has already announced plans to begin rolling out boosters in September for people who received the Moderna and Pfizer vaccines. People 18 years and older who got the Pfizer or Moderna vaccines will be eligible for a booster dose eight months after their second dose.
U.S. Surgeon General Vivek Murthy previously said health officials were concerned about "waning immunity and the strength of the delta variant," the highly contagious strain driving a surge of new infections.
The World Health Organization has called on countries to delay their plans for booster shots until nations with lower vaccination rates can immunize more of their population.
Just over 14 million people have received the Johnson & Johnson vaccine, the smallest share among the three vaccines being used in the U.S., according to the Centers for Disease Control and Prevention. The Pfizer vaccine has been administered to more than 205 million people, and nearly 144 million have gotten the Moderna shot, the CDC said.
Several independent researchers said the finding would probably support giving people boosters with the Johnson & Johnson vaccine. But they noted that with 17 volunteers, the study was relatively small. In addition, the study does not appear to have tested whether the increased antibodies would necessarily translate into increased protection in the real world.
"It would be reasonable to say that yes, have at least two doses of J&J, or have at least one more dose for those who had a single dose, including the option of having another J&J," said Saad Omer, a vaccine researcher at Yale. "It is pointing toward the utility of a second dose. I think that's reasonable."
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