A third dose of COVID-19 vaccine strengthened antibody levels among solid organ transplant recipients who had suboptimal antibody levels after the first or second dose, according to research published June 14 in Annals of Internal Medicine.
Researchers from Johns Hopkins Medicine in Baltimore evaluated 30 participants who had previously had an organ transplant and were taking immunosuppressants. All participants initially received the two-dose regimen or Moderna or Pfizer's vaccine, and were later given a booster dose of either those vaccines or Johnson & Johnson's shot.
Prior to receiving the booster shots, researchers tested all participants for antibodies against the spike protein: 24 patients had negative antibody levels and 6 had low-positive levels.
"Our findings revealed that a third of the participants who had negative antibody levels and all who had low positive levels before the booster increased their immune response after a third vaccine dose," said Dorry Segev, MD, PhD, senior study author and professor of surgery and epidemiology at Johns Hopkins University School of Medicine.
Twenty-three participants completed a survey a week after the booster dose was administered, reporting generally mild or moderate reactions. One case of mild organ rejection occurred during the study period.
Researchers emphasized the study only examined antibody levels, and that additional research is needed to see if the strengthened immune response after a booster shot actually lowers COVID-19 infection rates.
"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," said William Werbel, MD, lead study author and infectious diseases research fellow at Johns Hopkins medical school. "Therefore, we recommend that transplant recipients and other immunocompromised people continue to wear masks, maintain physical distancing and practice other COVID-19 safety measures."