J&J Vaccine: Real-world effectiveness and booster update


If you received the one-dose vaccine from Johnson & Johnson, we have some mostly good news.

Johnson & Johnson/Janssen issued data recently showing that in the real world, a single dose of the J&J vaccine was 77-80% effective for preventing moderate symptomatic infections and 79-84% effective for preventing hospitalization after several months. This was a big study of almost 400,000 people who received the J&J vaccine outside of the original clinical trial. It used 1.5 million unvaccinated people as a control group. And, the best news: this study was conducted over the summer when Delta variant was beginning to circulate, suggesting that J&J works well against Delta.

There was other evidence of the durability of the 1-dose J&J shot, too. In a separate (very) small lab-based study (read: in test tubes), researchers found that 8 months after getting a single dose of J&J, antibodies and T-cells remained strong, including neutralizing antibody responses against delta and other variants. In fact, neutralizing antibody responses to SARS-CoV-2 variants got *stronger* over the study period.

Interestingly enough, this paper notes that three of their 20 study participants showed a sharp increase in antibodies during the study. One of them had a mild breakthrough case of COVID-19, and the other two received an mRNA vaccine (even though that’s not officially recommended by anyone at this point). These results are not the focus of the study, but they offer clues that offering the immune system a refresher on what SARS-CoV-2’s spike protein looks like does increase antibody response. [These three people were excluded from the main results because the study wasn’t designed to look at the effectiveness of mixed dosing or the effects of breakthrough infection on immunity.]

So, what about boosters then??

J&J team researchers also released some data from their study of whether a two-dose strategy offered better protection, but the results on this one are about as clear as mud. People who got two shots with an 8 week interval between them had somewhere between *no better* protection and *much better* protection. It seems like this study didn’t have enough people enrolled to pin down whether 2 doses is better–which is puzzling and disappointing.

The company also conducted some lab tests of a booster dose given 6 months after the original single dose, and found that it increased antibody levels a whole lot. That’s good news for those of us awaiting a J&J booster.

The company says that they have submitted their results to the FDA, so if you’re waiting for news on a J&J booster, we hope it’s coming soon. We try not to offer opinions around here, but this one is unavoidable: we need to know whether people who got a one-dose J&J shot several months ago will be getting a booster and whether it will have to be J&J, or if we can boost J&J with an mRNA vaccine.

Here’s our previous take on boosters for J&J.




Helpful explainer on the effectiveness results from Dr. Michael Lin

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