Vaccine trials have historically faced challenges in adequately testing seniors over 75 years old, but recent efforts show improvement in including this age group to better understand vaccine safety and effectiveness for them. Older adults, especially those over 75, have unique immune system characteristics and health conditions that can affect how vaccines work, making it crucial that trials specifically evaluate this population.
One major issue is that many early vaccine trials often excluded or underrepresented the oldest seniors, focusing more on younger adults or a broad “older adult” category that lumps together ages 60 to 74 with those 75 and older. This can mask differences in vaccine response because immune function and health status can change significantly after 75. For example, immune senescence—the gradual weakening of the immune system with age—can reduce vaccine effectiveness and alter side effect profiles in this group.
Recent vaccine developments, such as those for respiratory syncytial virus (RSV) and COVID-19, have made strides in including seniors over 75 in their clinical trials. RSV vaccines approved in 2023 and 2024 specifically recommend vaccination for adults 75 and older, reflecting data from trials that showed meaningful protection in this age group. These vaccines demonstrated effectiveness ranging from about 68% to over 80% in preventing severe RSV illness and hospitalization among seniors 75 and older, indicating that trials did include sufficient numbers of this population to assess outcomes. However, the duration of protection and effectiveness in immune-compromised seniors remain areas needing further study.
Similarly, COVID-19 vaccine trials and subsequent real-world studies have increasingly focused on older adults, including those over 75, to ensure safety and efficacy data are relevant. Updated COVID vaccines continue to be recommended for seniors 65 and older, with ongoing monitoring to adapt formulations to circulating variants and immune responses in older populations.
Influenza vaccine research also highlights the importance of tailoring vaccine strategies for seniors over 75. High-dose influenza vaccines have been developed to provide stronger immune stimulation for the very elderly, as standard-dose vaccines may be less effective due to immune senescence. While high-dose vaccines show promise, data specifically stratified by age groups above 75 are still somewhat limited, and real-world effectiveness can vary by season and individual health status.
Despite these advances, challenges remain. Older adults over 75 often have multiple chronic conditions and varying degrees of immune system health, which complicates trial design and interpretation. Recruiting sufficient numbers of very elderl
