Johnson & Johnson said Wednesday that studies show a booster shot of its vaccine provides a "rapid and robust increase" in Covid-19 antibodies when used on people who have already received its first dose.
The interim data showed people who already had been given the J&J vaccine experienced a ninefold increase in spike-binding antibodies compared with 28 days after the first dose, the drugmaker said in a statement.
That increase was seen in trial participants ages 18 to 55, and in people over 65 who received a lower booster dose, according to the statement. The study was done early in anticipation of the need for boosters, the company said.
The findings have been submitted to the medical preprint publication MedRxiv.
Mathai Mammen, global head of Janssen Research & Development at Johnson & Johnson, said the company was looking "forward to discussing with public health officials a potential strategy" for deploying a J&J booster shot.
The drugmaker said it was "engaging" with the Food and Drug Administration and the Centers for Disease Control and Prevention, as well as the European Medicines Agency, which is the main regulator in Europe, and the World Health Organization, about using its shot as a booster.
Boosters are being planned in the United States as early as the fall for those who got the two-shot Pfizer-BioNTech and the Moderna vaccines.
J&J says that neutralizing antibody responses from its single-shot dose have been shown to hold up for eight months after immunization. And experts say that the evidence suggests the vaccine appears to be doing its primary job of keeping Covid patients out of hospitals and morgues.
There is some real-world data showing J&J’s shot holds up against the delta variant.
A huge study of health workers in South Africa showed the vaccine remained 71 percent protective against hospitalization from the variant and between 91 percent and 96 percent effective against death. And the researchers said the vast majority of breakthrough infections in vaccinated people were mild.
But last week U.S. Surgeon General Vivek Murthy said boosters "will likely be needed" for the J&J vaccine. And some Americans have already sought out additional doses of Covid vaccines after getting the J&J shot, essentially mixing and matching shots from different companies.
The J&J findings announced Wednesday showed a booster of the same type gave a sharp increase in the number of binding antibodies.
Unlike neutralizing antibodies, which destroy the virus, binding antibodies attach to the virus but do not destroy it or prevent infection. Instead, they alert the immune system of its presence so white blood cells can be sent to destroy it.
The results were released ahead of long-awaited results from J&J's large, two-dose vaccine trial. A spokesman told Reuters those results will be available in the coming weeks.