A day after a panel of the Food and Drug Administration's outside advisers voted to endorse the third doses of Moderna's COVID-19 vaccine, the committee voted unanimously Friday to back booster shots for the 15 million Americans with Johnson & Johnson's vaccine, at least two months after they were first vaccinated. The meeting of the FDA's Vaccines and Related Biological Products Advisory Committee came as new CDC data suggests infections and deaths among vaccinated Americans were worse in those who received Johnson & Johnson's COVID vaccine. While the unvaccinated were still 6.1 times more likely to test positive for COVID-19 and 11.3 times more likely to die from the disease compared to all fully vaccinated people, breakthrough cases of COVID-19 among vaccinated Americans have also climbed in recent months. Rates of cases and deaths among people who were vaccinated with Johnson & Johnson's dose were higher than in those who received two shots of vaccine from Pfizer or Moderna.
However, severe COVID-19 remains unlikely for most vaccinated younger adults. Hospitalizations in adults under 50 was just 1.8 per 100,000 fully vaccinated people, in the CDC's COVID-NET surveillance, compared to nearly 15 per 100,000 in seniors 65 and older.
"The overall perspective is that, regardless of whether or not there's been waning or if this was the true effectiveness after a single dose, the effectiveness or protection with a single dose of the J&J vaccine is not equivalent to protection, at this time, with either two doses of an mRNA vaccine," the CDC's Dr. Amanda Cohn told the panel.
Like with Moderna's authorization, recipients of Johnson & Johnson's vaccine will need to wait until the CDC issues formal guidance around use of the shots before boosters can be rolled out. The CDC's Advisory Committee of Immunization Practices is scheduled to meet Thursday to discuss COVID-19 vaccines.
"ACIP really can't expand or be broader than FDA's conditions of use. However, we can be more narrow. So for example, FDA could go down on age, and ACIP would not have to," Cohn told the FDA's committee on Thursday.
Johnson & Johnson told the panel that the company believed their vaccine remained effective against severe cases of COVID-19, with "consistent" and "durable" immunity that might not wane over time like the mRNA-based vaccines from Pfizer and Moderna. However, the company's top scientists acknowledged that there was "headroom to improve" the effectiveness of their shots, to reach levels similar to the other brands.
For Moderna and Pfizer's vaccines, FDA advisers have so far greenlit doses only for older adults and others at high risk of severe disease or exposure. But with Johnson & Johnson's second dose, the agency asked the panel for a vote on all adults — either two or six months after they were first vaccinated.
Early data from a small number of participants in Johnson & Johnson's trial suggest waiting six months or longer might "provide a more robust booster response." But the data also showed that a booster shot still provided a significant boost of protection after only two months.
The FDA said it had yet to finish independently verifying Johnson & Johnson's data, but officials on Friday cited "intense public interest and a sense of urgency in providing options for a second dose" to not wait to meet over the submission.
"When we have these booster submissions, we would generally be expecting data on an immunogenicity study of a few hundred subjects. Instead we have studies here, which involve thousands of patients, which would have taken the review team literally, probably, months to go through our normal process for," Dr. Peter Marks, the FDA's top vaccines official, told the committee.
After voting on Johnson & Johnson's request for emergency use authorization of a booster shot Friday, scientists presented the committee with early data on "heterologous" booster shot combinations -- giving additional doses of one brand to people who had been vaccinated with another. For example, could someone who received two shots of Moderna's vaccine receive a booster from Pfizer?
Preliminary results from the National Institutes of Health's trial, which were posted Wednesday as a preprint and have yet to be peer-reviewed, found that all combinations of Pfizer, Moderna and Johnson & Johnson's vaccines tested in the study's 458 participants appeared safe and effective at triggering a "substantial increase" in antibodies to fight the virus. All prompted similar, mostly mild side effects.
"Our study was never about making the case of, if a booster should be used. Our study was, if a booster is authorized or approved, does it matter what that underlying vaccine was," Dr. John Beigel, associate director for clinical research at the National Institute of Allergy and Infectious Diseases, told CBS News.
Beigel said scientists had worked through the weekend to finalize their manuscript ahead of booster shot decisions by both the FDA and the CDC, which also must weigh in next week before additional doses can be rolled out.
Only one combination tested in the study — people first vaccinated with Johnson & Johnson who received a second shot of the same vaccine — failed to reach antibody levels that might be needed for high protection against symptomatic disease. However, the study's authors cautioned that it was "not designed to directly compare responses between different booster regimens" and that the antibodies might be sufficient to shield against cases of severe COVID-19.
Beigel said antibodies from Johnson & Johnson's vaccine, which is based on a modified adenovirus, may peak later than from the mRNA-based Pfizer or Moderna vaccines. Protection from Johnson & Johnson's shot may rely on other parts of the immune system that could provide longer-lasting effectiveness.
More answers could come soon from the NIH's ongoing trial.
Beigel said the team was still working on analyzing blood samples that could offer a window into the cellular immune response prompted by the different booster shot combinations, beyond the neutralizing antibodies they reported on Wednesday. Trial participants will also be followed for a year, which could help scientists better understand how protection might change differently over time.
"We'll start getting a sense at three months, we'll know more at six months, to really understand that decline. To see if the decline in antibody over time is the same for mRNA versus the adenovirus vaccines," said Beigel.