The science has yet to be settled, experts say. "I think there are still open questions for those who are immunocompromised," Brownstein said. "Talk to your doctor -- especially if you're in the high-risk category." Dr. William Schaffner, professor of medicine in the division of infectious diseases at Vanderbilt University School of Medicine, explained that "when talking about people who are immunocompromised, that includes a large spectrum of disease, and there are no studies at the present time to indicate that an additional dose will benefit you or what sort of reactions you might get from an additional dose." For now, Schaffner firmly stands against the idea of an additional booster shot without formal recommendations. He emphasized that the CDC is yet to recommend any booster, under any circumstances at the present time.