Third Dose of COVID Vaccine Boosts Protection in Transplant Recipients

Researchers say an extra dose of two-dose COVID-19 vaccines may improve immune system protection for organ transplant patients, a group that's so far responded poorly to two-dose vaccines.

"Our findings suggest clinical trials are warranted to determine if transplant recipients should receive COVID-19 vaccine booster doses as standard clinical practice, similar to what is currently done with hepatitis B and influenza vaccinations for this population," said study lead author Dr. William Werbel. He is an infectious diseases research fellow at the Johns Hopkins School of Medicine in Baltimore.

People who receive a heart, lung, kidney or other solid organ transplant often take drugs to suppress their immune system and prevent rejection, but those drugs can interfere with the body's ability to make antibodies in response to vaccines.

In two previous studies, only 17% of transplant recipients produced sufficient antibodies after one shot of a two-dose COVID-19 vaccine, and only 54% produced sufficient antibodies after the second dose, researchers reported.

Even transplant recipients who produced antibodies had levels well below those typically seen in people with healthy immune systems, the findings showed.

In the new study, the researchers evaluated 30 transplant recipients who previously received two doses of either the Moderna or Pfizer/BioNTech vaccine. None had reported an illness or a positive test for SARS-CoV-2 prior to vaccination. All were taking multiple immunosuppressive medications to prevent organ rejection.

Between March 20 and May 10, all participants got a third dose of either one of the Moderna or Pfizer vaccines, or they got the Johnson & Johnson shot.

"A third of the participants who had negative antibody levels and all who had low positive [antibody] levels before the booster increased their immune response after a third vaccine dose," said study senior author Dr. Dorry Segev. He directs the Epidemiology Research Group in Organ Transplantation at Hopkins.

A week after receiving their third dose, 23 patients completed a questionnaire and some reported generally mild or moderate side effects. One patient had severe arm pain and another reported a severe headache. No patients reported fever or an allergic reaction.

There was one case of mild organ rejection, according to the report published online June 15 in the Annals of Internal Medicine.

Segev said the reactions seem acceptable, given the benefits that vaccines can confer.

Meanwhile, Werbel urged transplant patients and other immunocompromised patients to be careful.

"Although the third vaccine dose appears to raise the immune response of transplant recipients to higher levels than after one or two doses, these people may still be at greater risk for SARS-CoV-2 infection than the general population who have been vaccinated," he said in a Hopkins news release.

"Therefore, we recommend that transplant recipients and other immunocompromised people continue to wear masks, maintain physical distancing and practice other COVID-19 safety measures," Werbel added.