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CHICAGO — A booster dose of Johnson & Johnson's COVID-19 vaccine sharply increased levels of antibodies against the coronavirus, according to interim data from two small, early-stage trials, the company said in a press release on Wednesday.
J&J has been under pressure to produce evidence of whether a booster shot would increase protection from its one-shot vaccine as the U.S. government prepares to roll out a booster campaign next month. The company plans to discuss the data with U.S. regulators as it devises its booster shot regimens.
The preliminary data announced on Wednesday involved a total of 17 people. It found that a second dose of the J&J vaccine delivered six months after the first resulted in a ninefold increase in binding antibody levels over those seen 28 days after the first dose, the company said.
The company did not release data on whether a second dose of its vaccine increases levels of neutralizing antibodies, which block the virus from entering cells.
That data is still being analyzed, said Dr. Dan Barouch, a Harvard vaccine researcher who helped design J&J's COVID-19 vaccine, but who was not involved in the J&J booster study.
Unlike neutralizing antibodies, binding antibodies tag the virus for destruction by other parts of the immune system. Barouch said increases in binding antibodies typically correlate with increases in neutralizing antibodies.
Several countries, including the United States, have begun offering booster doses to vulnerable individuals, including the immunocompromised, as the delta variant has spread and some vaccinated people have become infected with SARS-CoV-2, the virus that causes COVID-19. But those campaigns have excluded the J&J shot because there has been no evidence that a booster helps increase vaccine protection.
U.S. Centers for Disease Control and Prevention advisers in particular have been waiting for word on how to advise immunocompromised individuals who received the J&J vaccine and are already recommended to receive a booster shot.
According to J&J, the studies released Wednesday showed significant increases in binding antibody responses in participants aged 18-55 and in those 65 years and older who received a lower booster dose.
The study summaries are being submitted to the preprint server MedRxiv in advance of peer review or publication in a journal.
The results were released ahead of long-awaited results from J&J's large, two-dose vaccine trial. A spokesman said those results will be available in the coming weeks.
In July, J&J published interim Phase 1/2a data in the New England Journal of Medicine that showed neutralizing antibodies generated by its vaccine remained stable eight months after immunization with a single dose.
"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," Mathai Mammen, head of research and development at J&J's Janssen pharma division, said in a statement.
"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."
Several scientists have raised concerns that individuals who got the J&J shot would need boosters. One study by a team from New York University found a "significant fraction" of blood samples from recipients who got the J&J shot had low neutralizing antibodies against Delta and several other coronavirus variants.
J&J said the company is working with the CDC, the U.S. Food and Drug Administration, the European Medicines Agency, the World Health Organization and other health authorities about delivering a booster shot with the Johnson & Johnson COVID-19 vaccine.
