Scientists at the Food and Drug Administration found Johnson & Johnson's coronavirus vaccine to be safe and effective in preventing COVID-19, confirming clinical trial results announced by the drugmaker last month and likely clearing the way for an emergency authorization in the coming days.
The review, released online ahead of a meeting of FDA advisers on Friday, is the most detailed look to date at the data from J&J's study, which enrolled approximately 40,000 volunteers in the U.S., South Africa, Brazil and five other Latin American countries.
The agency's advisers, a group of vaccine and infectious disease experts, will discuss the data at Friday's meeting and vote on whether the benefits of vaccination outweigh the risks. Recommendations from the committee for coronavirus vaccines developed by Pfizer and Moderna led the FDA in each case to issue emergency authorizations the very next day.
Clearance of J&J's shot, which is given via a single injection and can be stored at refrigerator temperatures, would boost an immunization effort in the U.S. that's still hampered by limited supplies of Pfizer's and Moderna's vaccines.
In their 62-page analysis, FDA reviewers affirmed the 66% overall efficacy previously reported by J&J, while detailing rates of protection across different groups of participants and for emerging coronavirus variants.
Study investigators measured the shot's efficacy by counting cases of moderate or severe COVID-19 beginning two weeks after participants received either the vaccine or a saline injection. Of the 464 volunteers who got sick, 116 had received J&J's vaccine and 348 were given placebo. Two hundred fifty-nine moderate or severe cases were reported after 28 days, 66 of which were in the vaccine group.
Efficacy was similar across age groups and participants of different race or ethnicity, the FDA said. Vaccination appeared less protective in volunteers 60 years and older who had underlying conditions that put them at risk, although agency staff noted some uncertainty in the data.
Notably, the review showed there were no hospitalizations related to COVID-19 among vaccinated participants beginning 28 days after they received their shot, compared to 16 cases among those who got placebo. None of the vaccinated volunteers died from COVID-19.
Protection was also much stronger against severe COVID-19 alone, with vaccine efficacy calculated at 77% beginning after 14 days and 85% after 28 days.
Both the FDA and the advisory committee will be closely examining data from study participants in South Africa and South America due to the growing prevalence of coronavirus variants that appear to be more transmissible and weaken the potency of vaccines.
In South Africa, where infections with the variant known as B.1.351 accounted for nearly all observed cases, J&J's vaccine was found to be only 52% effective after two weeks and 64% after four weeks. That latter figure is somewhat higher than what J&J initially reported last month.
If only severe or critical cases are counted, however, protection was much higher: 73% after 14 days and 82% after 28 days. FDA reviewers, while acknowledging the reduced protection compared to the original SARS-CoV-2 strain, emphasized this point.
The most common side effects reported by vaccinated participants were injection site pain, headache, fatigue and muscle pain, according to the FDA's review. Nearly all were mild or moderate in nature, however, with only about 2% of systemic side effects classified as Grade 3 or higher.
The documents released by the FDA on Wednesday also shed new light on a severe side effect that led to a brief pause in J&J's study last October. A volunteer experienced a blood vessel blockage in his brain that doctors discovered 21 days after he received J&J's shot. The clot led to a cerebral hemorrhage, seizures and other complications.
Trial researchers stopped the trial to determine whether the vaccine was the cause, but concluded it was unrelated after an investigation.
The U.S. has pre-ordered 100 million doses of J&J's vaccine, 20 million of which the company expects to deliver by the end of March. Only 4 million or so will be ready to ship upon authorization, however, a company executive told lawmakers at a Congressional hearing on Tuesday.