A team of physician-scientists has found that solid organ transplant recipients, who were vaccinated, experienced an almost 80 per cent reduction in the incidence of symptomatic COVID-19 infection compared to those who were unvaccinated.

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"Persons who have received an organ transplant are considered to be at increased risk for COVID-19 and for a severe outcome because their immune systems are necessarily suppressed to ensure their transplants are successful and lasting," said Saima Aslam, Professor of Medicine at University of California San Diego School of Medicine. "These findings offer strong evidence that getting vaccinated provides significant protection," Aslam added.

For the study, published in the journal Transplant Infectious Disease, the team examined clinical data encompassing 2,151 solid organ transplant recipients, including kidney, liver, lung and heart. Of this total number, 912 patients were fully vaccinated and 1,239 were controls (1,151 were unvaccinated and 88 partially vaccinated). Nearly 70 per cent of the vaccinated patients received the mRNA-1273 vaccine (Moderna).

During the study period, there were 65 diagnosed cases of COVID-19 among the organ recipients: four among fully vaccinated individuals and 61 among the controls (two involving partially vaccinated individuals). There were no deaths among the breakthrough COVID-19 cases, but two among the 61 control cases.

"These findings are encouraging... first, it demonstrates real-world clinical effectiveness of COVID-19 vaccination in a vulnerable population. Second, the effectiveness is better than expected, given that studies have found that only about half of solid organ transplant recipients develop detectable anti-spike antibodies after vaccination," said Kristin Mekeel, chief of Transplant and Hepatobiliary Surgery at the varsity. Aslam said the results underscore the importance for transplant patients to get vaccinated against COVID-19 and to not focus on antibody levels alone.