Experts say viruses like influenza and RSV hit older adults harder because of age-related decline in the immune system (immunosenescence) and an increased likelihood of having chronic conditions, such as diabetes and heart disease. But not everyone's immune system declines at the same rate, says NFID Medical Director William Schaffner, MD. "An active 80 year old may have less immune system decline than a frail 65 year old," said Schaffner. "But staying active only helps so much—if you're over 65 it is vital that you boost your immune system by getting vaccinated as recommended." There are currently several types of flu vaccines available in the U.S. including two that are specifically recommended for the 65+ population—one (high-dose) that provides a four-times higher dose than the standard vaccine and another that includes an adjuvant, an ingredient that helps create a stronger immune response in the body. Public health officials do not recommend one specific vaccine over another. "Adults age 65 years and older may receive the high-dose or adjuvanted vaccine if they are available, but should not skip their annual flu vaccination in any case," says Dr. Schaffner.