The data that Johnson & Johnson submitted to the Food and Drug Administration for its emergency use authorization was made public Wednesday.
Looking at the data, there are many different ways it could be compared to the Pfizer and Moderna vaccines.
The FDA’s initial goal was a vaccine with a 50% efficacy. Overall, the Johnson & Johnson vaccine has a 66% efficacy 28-days after the single dose is given. It’s lower than the 94-95% efficacy of the Pfizer and Moderna vaccines seen two weeks after the second dose.
The Johnson & Johnson study looked at 40,000 participants -- half received the vaccine and half received a placebo. The study was done in multiple countries, including the United States, South Africa and Brazil -- that’s important, because of the emergence of more contagious variants and the possibility they could make the vaccine less effective.
The Johnson & Johnson vaccine had a 72% efficacy in the U.S., compared to 64% in South Africa, where the highly contagious variant is dominant.
Another way to compare is to look at how well it prevents severe disease. In that respect, the Johnson & Johnson vaccine was 85% effective -- especially in people under 60-years-old, where it was 92% effective.
It also had a lower efficacy in people with comorbidities, with 59% compared to 69%.
The study also looked at the question of whether the vaccine could prevent asymptomatic infection, which is important to limit silent spread. They found the Johnson & Johnson vaccine appeared to be 74% at preventing asymptomatic infection, but they didn’t feel confident in the number due to limited follow-up time and sample collection.
What about side effects?
The most common side effects of the Johnson & Johnson vaccine were pain at the injection site, headache, fatigue, muscle aches, nausea and fever -- all of the side effects were more common in people who got the vaccine compared to the placebo.
Notably, the rate of the side effects with the vaccine were significantly lower than the percentage of people who reported them in the Pfizer and Moderna studies, but just like in those studies, the side effects were more common in younger participants.
Many viewers have asked if the side effects are more common in people who previously were infected with COVID. While neither the Pfizer nor Moderna data could answer that question, the Johnson & Johnson study had 154 vaccine recipients who had antibodies to coronavirus and there was no difference in reported side effects.
While no serious concerns about safety were found, there were things the FDA will likely monitor as the vaccine rolls out:
- Six people who received the vaccine reported tinnitus. No one in the placebo group reported tinnitus.
- 15 blood clots were seen in the vaccine group, compared to 10 in the placebo group.
The study isn’t enough to determine if there is a casual relationship between the vaccine and either tinnitus or blood clotting, but it will be monitored.