I wonder how does getting 2 or 3 shots of the Pfizer or Moderna COVID vaccine compare against 1 shot Johnson & Johnson's vaccine + 1 or 2 shots of Pfizer or Moderna, in terms of COVID-19 protection. I'm mostly interested in the COVID-19 delta variant.

I couldn't find anything on it on Google. My findings:

1 Answer 1


The Astra Zeneca vaccine which is similar to Johnson & Johnson's, was studied in combination with Pfizer's; they found using Pfizer as the second dose after a first dose of AZ gave better results than two doses of AZ: https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3874014 "Safety and Immunogenicity Report from the Com-COV Study – a Single-Blind Randomised Non-Inferiority Trial Comparing Heterologous And Homologous Prime-Boost Schedules with An Adenoviral Vectored and mRNA COVID-19 Vaccine"

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    Great information, thanks! Commented Aug 13, 2021 at 2:38
  • Thanks. Can effective COVID 19 booster be manufactured by mixing and matching vaccines of different vaccine manufacturers? Commented Aug 19, 2021 at 12:33

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