Opinion | J&J vaccine recipients deserve clear guidance on booster shots

To that point, data are emerging that for people who received an initial adenovirus vector vaccine, a second dose with an mRNA vaccine would enhance immunity. While we don’t have results yet of mixing one dose of J&J with an mRNA vaccine or two doses of J&J, there are studies that examined mixing another adenovirus vector vaccine, AstraZeneca, with Pfizer. Interestingly, the mix-and-match approach elicited a stronger immune response than two doses of the same vaccine. In Germany and Britain, patients have been receiving the mixed regimen without major safety outcomes.