Responsiveness to second and third dose of mRNA COVID‐19 vaccination in adolescent and young adult heart transplant recipients

Background Third‐dose mRNA COVID‐19 vaccine is currently recommended in the United States for SOT recipients based in part on data showing diminished immune response, including Ab production, after a two‐dose regimen. Data on vaccine response in adolescent and young adult SOT recipients are limited, including no data reported on third‐dose responsiveness. Methods Results of serologic testing in a convenience sample of 28 vaccinated adolescent and young adult HT recipients at a single institution were collected from the medical record and summarized. Results At a median of 98.5 days (IQR 59–150) after second dose, 17 (61%) had an Ab response. Among 12 who had serology before and after third‐dose vaccination, four of seven who were negative prior to third dose became positive at a median of 34 days (IQR 31–39.5) following third dose. No myocarditis, acute rejection, graft dysfunction, graft loss, or deaths were observed. Conclusions These findings support recommendations for the routine administration of three doses of mRNA vaccines in adolescent and young adult HT recipients and show a potential subpopulation in whom the fourth dose should be contemplated.