This graph conveys a lot of information in a compact way. This study directly compared antibody levels in various groups of people, including:
- Those who provided samples before the pandemic
- People with prior covid but no vaccine
- People with one or two doses of Moderna or Pfizer, or one dose of J&J, both in those with and without prior covid
Samples from vaccinated people were taken a median of 24 days post vaccination.
The antibody test they used was the Roche (Labcorp 164090) test, with the addition of as many dilutions as needed to prevent the test from maxing out.
They confirm what I've been seeing with my data using the same test. Moderna gives antibody levels that are a bit higher than Pfizer. J&J is lower, and a surprising number of healthy people who had J&J without prior covid are coming out very low. Their average for J&J was even lower than mine. This may be due to their sampling at 24 days. J&J has a bit of a slow burn.
A single dose of Moderna or Pfizer in people who have prior infection gives antibody levels in the 20-30 thousand range. Pfizer has informally reported similar levels for the phase 1 trial of their third shot, so I think it's reasonable to think that I will have those levels soon, but I have no way to test for greater than 2500.
Interestingly, two of the approx 1200 pre-pandemic samples were weakly positive (in the 10-20 range). Probably that is cross-reactivity with a cold coronavirus. No test is going to be perfect.
People with past covid averaged 198, which is similar to what I've been seeing.
They also measured T-cell responses, and these unsurprisingly correlated with antibody responses: highest in Moderna and lowest in J&J.
Link to study : https://www.medrxiv.org/content/10.1101/2021.07.18.21260732v1.full.pdf