http://www.sciencemag.org/news/2021/07/transplant-patients-higher-rate-covid-19-breakthroughs-boosts-case-booster-vaccines

Doctors recommend that organ transplant patients like liver recipient Andrea Lopez Robles of Madrid continue to take precautions such as wearing a mask and social distancing even after they are fully vaccinated. 

Transplant physicians have worried for months that their patients might not be getting the protection they need from COVID-19 vaccines. Studies have already shown that many organ recipients don’t produce coronavirus-fighting antibodies even after two doses of the highly effective messenger RNA (mRNA) vaccines—an indication their bodies are unable to mount a strong defense against SARS-CoV-2. A study out today indicates this lack of antibodies is indeed translating to a much higher risk of “breakthrough” cases of COVID-19 among vaccinated transplant recipients.