Thread by @DrEricDing

UNDERRATED BENEFITS of J&J vaccine on severe illness— lost in efficacy comparisons is how the J&J vaccine efficacy actually may **get better over time** for severe #COVID19–as high as 90-95% at 56 days—trend is very strong. And makes J&J on par w/ Pfizer-BioNTech & NIH-Moderna.🧵

2) And do we see that in the table? Yes... in all countries, the efficacy of J&J vaccine against severe #COVID19 was always higher after 28 days than after 14 days: Rising from 70’s to mid-upper 80’s%.
fda.gov/media/146219/d…

3) Let’s look at the Pfizer-BioNTech vaccine for 14-27 days & severe #COVID19 outcome... it was just 62-80% for severe in Israel, on par if not lower than J&J. And for >35 days with 2nd shot? 92% against severe, on par with J&J that only used 1 shot without any booster.

4) Do we see J&J performing strong on hospitalization, ICU, mechanical ventilation? Yes. In fact, 28 days after vaccination with J&J, zero events, which means de facto 100% efficacy.

5) Also keep in mind the large number of variants during the more recent era of the J&J vaccine. 46-59% of all cases were variants. And 96% of the South Africa 🇿🇦 trial’s 59% cases that were variants - was the infamous #B1351 variant!

6) But wait, didn’t we just see the J&J vaccine being 64% efficacious overall and 81.7% efficacious against severe #COVID19 in South Africa 🇿🇦 after 28 days? YES!!!

That means the J&J vaccine is quite good even for the #B1351 variant that was 56% of all cases in SA!

7) Also, if we truly compare apples to apples on days since first shot, while the Pfizer vaccine showed 92% after 35 days (7 after 2nd booster)—yet J&J efficacy matched that range if average all of its efficacy range after its 35 days (with only 1 shot!)

8) Furthermore, the J&J trial was done in a middle of the WORST SURGE periods in each country that implemented the J&J trial! What does this matter? In epidemiology, we call this high background rate—which can skew efficacy vs the Pfizer/Moderna trials with low rates—here is how:

9) Suppose Pfizer prevented 9 cases... 10 cases in placebo, 1 in vaccine—90% efficacy.

But if J&J was carried out when rates are high, then could be 20 cases in placebo, and 11 in J&J vaccinated—The efficacy is then 45%!

(This is what happens it yields absolute risk decrease)

10) So don’t be disappointed by the lesser 66% efficacy.... that is dragged m down by all the circumstances above (not J&J fault).

➡️Also don’t forget that if we prevent a severe case, that case then usually less severe right? EXACTLY—hence why we see J&J hugely lower symptoms!

11) Think of this analogy—if a drug or special diet prevents / treats obesity.... there will then be MORE moderate overweight people (only small reduction in overweight %)... But that is because tons of formerly obese dropped down to overweight category!!! here severe➡️moderate.

12) Going back to the high baseline rate issue of the J&J vaccine, I had laid out a situation above where absolute risk difference doesn’t change but RR did. Granted, but high background rate can weaken the RR too—e.g. much greater chance of stacked exposure doses & exposed load.

13) What I mean by that is—with high rates in community, a vaccinated person could get exposed a lot more & multiple times—greater virus dose and increasing chance of successful infection—if community rates high. This maybe also led to lower overall JJ efficacy.

14) Also was the Pfizer vaccine perfect for severe disease in the original FDA approval submission for EUA? No... after 2 doses... 35 days after first shot... it was ~75% against severe, and 88.9% against severe anytime after 1 shot. Par with J&J.
fda.gov/media/144245/d…

15) Johnson & Johnson vaccine deliveries nationwide begins today!!! #CovidVaccine #COVID19

(video: UPS center in Louisville, Kentucky)

16) To be clear, J&J matches Pfizer & Moderna on severe disease efficacy over time. But why do I think J&J is likely as good also for moderate/milder #COVID19 too? Because J&J was tested during the PEAK SURGE periods of countries. I explained reasons above, but here is analogy:

17) ANALOGY: Vaccines are like a chest body armor—they can block some bullets (virus attack) but they can’t block a large number of automatic machine gun bullets. Vaccines protect most of time, but sometimes mild infections can happen. But without armor, you’re very vulnerable...

18) But J&J was tested during a period of peak exposure and virus prevalence (constant barrage & multiple exposures, more dose), while Pfizer/Moderna trials were during more modest infection periods (fewer bullets to block, plus also fewer armor penetrating #B1351 variants).

19) Hence, J&J had more “armor failure” —because it was used during period of heavier bombardment than Pfizer/Moderna.

Meanwhile, placebo without any armor, any number of bullets can pierce your body.

That’s the theory speaking to folks folks. J&J likely just as good as mRNA.

20) They are testing a booster for J&J. The other two adenovirus vaccines by Oxford & by Russia - Sputnik V - have a 2nd shot. But just one shot is still very good. The increase in efficacy over time is quite strong (top post), but I won’t be surprised if they roll out boosters.