Morbidity and mortality from SARS‐CoV‐2 infection in heart (HT) and lung transplant (LT) recipients are high, especially for LT recipients, despite vaccination. 1 Despite severe COVID‐19 outcomes, HT/LT recipients represent <10% of solid organ transplant recipients (SOTRs) included in cohort studies evaluating two and three dose regimens. 2 There is now strong evidence to support that SOTRs in a greater immunosuppressed state (common among HT/LT recipients) are at increased risk for persistent seronegative state post‐D3. 3 , 4 Therefore, we evaluated antispike antibody responses before and after a third vaccine dose (D3) in HT/LT recipients to quantify post‐D3 antibody responses.