Thread by @MonicaGandhi9

HETEROLOGOUS VACCINATION (means one dose of one type of vaccine & 2nd dose of another type of vaccine): Paper came out today (mix & match) that finally looked at J&J + mRNA vaccine together; 1st let me tell you about studies in past which examined this with AztraZeneca + mRNA

Study from the UK (Com-CoV) looked at an adenovirus DNA vaccine (examples are AztreZeneca (AZ) J&J, Sputnik V - in this case it was AZ) and the mRNA vaccine (only two examples are Moderna + Pfizer, in this case studied Pfizer) 28, 84 days (4,7 wks) apart
papers.ssrn.com/sol3/papers.cf…

Did combination in the 4 ways (Pfizer/Pfizer, AZ/AZ, AZ/Pfizer, Pfizer/AZ) and found that the best combination in terms of both neutralizing antibody titers AND T cells was AZ then Pfizer (so adenovirus/DNA then mRNA). 2nd study from Spain, summary here
nature.com/articles/d4158…

Looked at AZ vaccine followed at least 8 weeks later by a Pfizer vaccine (look at that nice spacing interval between doses) and this combination triggered higher antibody responses than AZ vaccine alone (don't see T cells measured). 3rd study from Germany
medrxiv.org/content/10.110…

measured cellular immunity and antibody responses with different mix/match regimens of AZ, Pfizer and Moderna (duration between doses was shorter for two mRNA vaccines 4 weeks then those that used AZ ~ 11 weeks). Strongest antibody & T cell response with AZ then mRNA like in UK

Study today from NIH looked at combinations of J&J, Moderna and Pfizer (2 shots apiece, homologous or heterologous, doses >= 12 weeks apart). Seen before: 2 Moderna doses when evaluating homologous combos gave he highest neutralizing antibody response
medrxiv.org/content/10.110…

Of heterologous combos, rise in neutralization antibodies greatest for those who got the J&J followed by an mRNA vax(compared to two J&J doses). Table below- important to note T cells not reported here but consistent with previous data that DNA followed by mRNA more immunogenic

Biggest limitation? T cell immunity not measured (although T cells needed to help B cells produce antibodies); clinical outcomes not measured; neutralizing antibodies don't tell whole story. All combos gave titers that are likely protective (>100) but J&J + mRNA strong combo