‘Mix and match’ Covid vaccine boosters are effective, NIH study finds


A highly anticipated study on “mixing and matching” Covid-19 vaccines found the approach to be safe and effective, though the Moderna and Pfizer-BioNTech vaccines were found to spark a stronger immune system response than Johnson & Johnson.

Mixing and matching refers to giving a booster dose of a vaccine that’s different from the vaccine type that was used for the initial vaccination series.

The National Institutes of Health study, which was released Wednesday and has yet to be peer reviewed, found that people who received the Johnson & Johnson vaccine produced stronger antibody levels after receiving a booster shot made by Moderna or Pfizer, compared to a booster from Johnson & Johnson. Those who were originally vaccinated with the Pfizer or Moderna vaccines and received either company’s booster shot produced comparably strong immune responses, the researchers observed.

The study, credited to 37 doctors and academics, followed 458 volunteers and measured their antibody levels two weeks and four weeks after the boosters were administered. The booster shots were given four to six months after the original vaccinations.

Individuals were divided into different groups based on their original immunizations and were given one of three boosters made by Pfizer, Moderna or Johnson & Johnson. For instance, those who were originally vaccinated with Pfizer’s two-dose regimen received either a matching Pfizer booster or a “mixed” one from either Moderna or Johnson & Johnson.