On Dec. 5, 2021, Johnson & Johnson announced preliminary results from an independent study, including a subset of participants from the Janssen-sponsored COV2008 study, conducted by Dan Barouch, M.D., Ph.D., et al. of Beth Israel Deaconess Medical Center, which showed that a booster shot of the Johnson & Johnson COVID-19 vaccine (Ad26.COV2.S), administered at six months after a two-dose primary regimen of BNT162b2, increased both antibody and T-cell responses.

These results demonstrated the potential benefits of heterologous boosting (mix-and-match). The article describing these results was posted on medRxiv.