The J&J vaccine is <10% of vaccinations in the US, and ~0% outside, so it isn't studied as much as other vax. In particular how well J&J works against Delta (b.1.617.2) hasn't been discussed, whereas we know a lot about Pfizer/Moderna/AZ. So I've decided to take a stab at it.
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2) I was motivated by this CNN article which revealed recent findings that the Pfizer/BioNTech vaccine (and likely the similar Moderna) are 88% protective against symptomatic Delta infection after dose 2 (good), but only 33% after dose 1 (not so good)
cnn.com/2021/06/10/opi…
3) The article says "Of note, this variant appears to be extremely transmissible, and the first dose of a two-dose vaccine regimen is much less effective than is the first dose against other variants." What about J&J which only has 1 dose?
4) Will 1-dose J&J act more like the first dose of a two-dose RNA vaccine regimen against Delta (33% protection) or more like the second dose (88% protection)?
My best guess is that it will be 64%. Why?
5) The J&J vax is 64% effective against Beta (501Y.V2 from South Africa) when looking ≥1mo after vaccination (vs 66% for original). Beta has a E484K mutation that reduces potency of neutralizing antibodies (nAbs) elicited by the J&J vax by ~5x.
rupress.org/jem/article/21…
6) The Delta variant has a nearby mutation T478K that reduces nAb potency by 6x. So escape from nAbs by Beta and Delta are very similar.
7) So because Delta and Beta resists nAbs similarly, we might expect J&J efficacy against symptomatic Delta might be similar to that against Beta: 64%. Protection against severe disease would be predicted to be similar, at 82%.
9) It's not known why J&J didn't show much efficacy drop from original to Beta with the 5x drop in nAb potency. This contrasts with the drop in 1-dose RNA vax efficacy from 80% on original to 33% on Delta being predicted by nAb potency drop alone.
nature.com/articles/s4159…
10) It could indicate that J&J elicits better cellular immunity than the RNA vax, but this is just speculation. It would be nice if studies can be performed on the post-J&J T-cell and nAbs responses against original and B.1.617.2 so we can tell.
@michaelmina_lab @florian_krammer
p.s. J&J efficacy numbers taken from below article
nejm.org/doi/full/10.10…
There's an assumption in the analysis that if J&J is remaining effective against variants due to cellular immunity, then Delta won't resist that any more than Beta. Many mysteries with this vaccine.
Dr. Barouch (ex-classmate, running studies of J&J vax at Harvard) also concludes the robust T cell immunity may account for J&J maintaining efficacy against Alpha and Beta variants. If so, then likely will be true for Delta as well. bostonglobe.com/2021/06/09/nat…
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