According to results from a small study published in Annals of Internal Medicine, an extra dose of COVID-19 vaccine may boost protection in patients who have undergone solid organ transplants.
Of the 24 patients enrolled in the study who appeared to have no protection after two doses of mRNA vaccine, one-third (n=8) developed some antibodies after receiving an additional dose. A third shot also provided a boost in immunity to another six patients who had minimal antibodies after the first two vaccine doses.
These results are limited by the absence of assays for neutralizing antibody, B-cell memory, and T-cell responses, the authors wrote. Still, "it's very encouraging," said Dorry Segev, MD, PhD, a transplant surgeon and coauthor of the study. "Just because you're fully negative after two doses doesn't mean that there's no hope."
Patients taking immunosuppressive medications post-transplant or in cancer treatment were excluded from initial testing of the vaccines. Recently, researchers at Johns Hopkins found that a little more than half of patients harbored antibodies after two doses of the Pfizer or Moderna vaccines.