ABSTRACT
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.