Here is an article about a recent study aimed at determining the effectiveness of third-dose COVID-19 vaccine boosters for organ transplant recipients.
- Transplant patients see boost in COVID-19 protection after 3rd vaccine dose, study suggests https://www.cbc.ca/news/canada/toronto/transplant-patients-see-boost-in-covid-19-protection-after-3rd-vaccine-dose-study-suggests-1.6138089

Here's the study from the New England Journal of Medicine
- Third Time’s a Charm — Covid-19 Vaccine Hope for Solid-Organ Transplant Recipients https://www.nejm.org/doi/full/10.1056/NEJMe2112866