Courtesy: Getty Images (CNN) — A third dose of coronavirus vaccine could help boost antibody levels among some organ transplant recipients who have not had robust responses to the standard vaccination schedules, a new study suggests. Among patients in the study who had no measurable antibodies after receiving two doses of vaccine, one-third of them saw a rise in antibodies after a third dose -- and among those with low antibody levels after two doses, all of them saw an increase after a third dose. The findings were published Monday in the journal Annals of Internal Medicine. Organ transplant recipients might not have an adequate response to coronavirus vaccines because they take drugs to suppress their immune systems. That helps reduce the risk of the body rejecting new organs but may also limit responses to vaccines.