A second dose of Johnson & Johnson's coronavirus vaccine is likely beneficial to recipients, the Food and Drug Administration (FDA) said Wednesday, thoughthe data is extremely limited.
In a briefing document released ahead of an advisory panel meeting later this week, the FDA said it relied heavily on studies conducted by Johnson & Johnson and could not independently confirm many of the findings because data from the trials were not submitted in time.
The staff report indicated that the evidence was likely stronger for the effectiveness of a booster of Johnson & Johnson's vaccine than for the mRNA vaccines from Pfizer-BioNTech and Moderna.
"Although not independently confirmed by FDA from datasets, summaries of the data suggest there may be a benefit in a second dose administered approximately 2 months after the primary dose," FDA staff scientists wrote.
In an unusual move, the agency scheduled the meeting of its outside advisers before the company had even submitted its application for a booster dose, leading to the time crunch.
Friday's meeting of FDA's advisory committee will likely conclude with recommendations to the agency about the necessity of a booster dose of the single-shot vaccine and the timing to administer it.
While touted for its ease of distribution, Johnson & Johnson's vaccine has from the start had a lower effectiveness compared to the mRNA vaccines, leading experts to believe a booster would likely be needed at some point.
"Overall, data indicate that the Janssen COVID-19 vaccine still affords protection against severe COVID-19 disease and death in the United States, although the highest effectiveness estimates (including for more severe COVID-19 disease) across clinical trials and real-world effectiveness studies evaluating the Janssen COVID-19 vaccine are consistently less than the highest effectiveness estimates for the mRNA COVID-19 vaccines," FDA staff wrote in the report.
While the vaccine provides protection against severe disease for at least six months, the company said a decrease in protection over time against cases that include moderate COVID-19 was observed globally, which could be driven by waning protection or reduced efficacy against emergent SARS CoV-2 variants.
Vaccine efficacy against moderate and severe/critical COVID-19 decreased from 66.9 percent to 56.3 percent at the final analysis.
Johnson & Johnson said a booster is recommended "at 6 months or later, based on the strength of the immune responses" for people ages 18 and older.
However, the company also said a booster may be administered as early as two months after the initial dose, and the advisory panel will discuss that evidence during the meeting.
The FDA said there was one study that showed a lower increase in antibodies after two months compared to when a booster it was administered after six months, but sensitivity issues with the test used to conduct the analysis means the levels can't be directly compared
FDA scientists also suggested there wasn’t enough data on the older people or on the impact of a booster on the delta variant to draw a definitive conclusion on the benefit.
The FDA advisory group is scheduled to discuss the J&J data on Friday, after meeting Thursday to discuss the data on Moderna's submission for authorization of a booster.
Unlike with Johnson & Johnson, the FDA report did not take a position as to the benefit of a booster dose of Moderna, because there's limited evidence that protection is waning. But the panel raised similar concerns regarding Pfizer's booster request, which still ended up being authorized.
The agency could make a final decision within days of the meetings. Then, the Centers for Disease Control and Prevention and its vaccine advisory committee will meet and make their own decision, likely next week.