Thread by @celinegounder

1/ PRE-PRINT results on NIH's mix & match COVID vaccines study:

medrxiv.org/content/10.110…

https://twitter.com/celinegounder/status/1442920120909582337?lang=en

2/
Matched (same) vaccine:
⬆️neutralizing antibody levels 4-20x

Mixed (different) vaccine:
⬆️neutralizing antibody levels 6-76x

3/ Best boosts?

Based on neutralizing antibody titers at day 15 after boost:

After Moderna:
Moderna > Pfizer > J&J

After J&J:
Moderna > Pfizer >>> J&J

After Pfizer:
Moderna > Pfizer > J&J

4/ Note that this study looks only at binding and neutralizing antibody titers out to 15 days after boost.

Data on 29 days after boost are pending for some of these groups, so can't compare out that far yet.

5/ We don't know how much antibody levels will wane (AND THEY WILL) over time for each group.

We also don't know what the impact of these booster doses is on B- and T-cell immunity,

or risk of infection, symptomatic disease, hospitalization, or death.

6/ We also don't know if boosters performed differently by demographic group (e.g. elderly, immunocompromised).

And this only looked at binding and neutralizing antibody titers vs D614G (early variant) not vs the Delta, Beta, or other variants.

7/ Note that the study participants were overwhelmingly white.

All were considered healthy.
(So I assume that means none had underlying co-morbidities–like heart disease, diabetes, or obesity–that would predispose to severe disease if one were infected?)

8/ One more point on neutralizing antibody titers:

These are a reflection of:
Quantity of antibodies
Affinity of antibodies
Breadth of antibodies

It would be interesting to see affinity vs breadth of antibodies by regimen.