ACP Now Recommends RSV Vaccine for All Adults 75 and Older, With Nuanced Guidance for Younger Groups
RSV - respiratory syncytial virus - has long been associated primarily with childhood illness. Its burden in older adults tells a different story. Each year in the United States, an estimated 170,000 adults aged 50 and older are hospitalized with RSV, and roughly 14,000 die. For adults 75 and older, the risk of severe lower respiratory tract infection is particularly elevated, especially in those living in long-term care facilities or managing chronic conditions including kidney disease, cardiovascular disease, and diabetes.
The American College of Physicians has now issued updated practice points, published in Annals of Internal Medicine, that translate the available evidence on RSV vaccines into specific clinical guidance. The core recommendation is unambiguous: all adults aged 75 or older should receive a protein subunit RSV vaccine. For those aged 60 to 74, the guidance is more conditional - those at increased risk for severe RSV may consider vaccination, with the decision shaped by individual health circumstances.
Why Protein Subunit Specifically
Multiple RSV vaccine formulations have been authorized for adults, including mRNA-based and adjuvanted recombinant protein vaccines. The ACP's guidance targets protein subunit vaccines specifically, reflecting the evidence reviewed by the Population Health and Medical Science Committee. The committee conducted a rapid review through the ACP Center for Evidence Reviews covering efficacy, comparative effectiveness, and harms in adults who are not pregnant or immunocompromised.
The committee weighed both benefits - reduction in RSV-related hospitalization and severe illness, contribution to all-cause mortality reduction - and harms, including the small but nonzero risk of Guillain-Barre syndrome, a rare neurological condition associated with some vaccines. For adults 75 and older, the benefit-harm balance clearly favored vaccination. For the 60-74 age group, the absolute benefit is lower because severe RSV is less common at younger ages, while the harms remain comparable. That asymmetry explains the more nuanced guidance for middle-aged adults.
Unlike influenza vaccines, which are administered annually as viral strains change, RSV vaccines are currently administered once. Whether and when repeat vaccination will be needed is under active study.
Breast MRI: Modest Additional Benefit, More False Positives
The same issue of Annals of Internal Medicine includes research directly relevant to breast cancer screening policy, particularly in light of new federal requirements that patients be notified of their breast density. Using Breast Cancer Surveillance Consortium data with three simulation models, researchers funded by the National Cancer Institute compared digital breast tomosynthesis (3D mammography) alone versus 3D mammography combined with MRI for women ages 40 and older at average to four times the average breast cancer risk.
The findings were measured in their conclusions. Mammography alone prevented the majority of breast cancer deaths. Adding MRI provided modest additional benefit but also generated more false-positive biopsy recommendations - a meaningful harm given the psychological and physical cost of unnecessary procedures. When MRI was added specifically for women with extremely dense breasts and at least double the average cancer risk, the balance of benefits and harms became comparable to standard mammography screening for the average-risk population. The researchers concluded that supplemental MRI could be reasonable for higher-risk women with dense breasts, particularly if the costs of MRI and rates of unnecessary biopsies can be reduced.
Metformin Does Not Treat Established Long COVID
A third study in the same issue delivers a negative result with direct clinical relevance. A randomized trial conducted at two South Korean hospitals between July 2024 and January 2025 enrolled 396 adults with persistent long COVID symptoms and randomly assigned them to two weeks of metformin, ursodeoxycholic acid (UDCA), or placebo in a double-blind design.
After eight weeks of follow-up, recovery rates and symptom improvements were statistically indistinguishable across all three groups. Neither drug outperformed placebo. This is notable because earlier observational evidence had suggested that metformin taken during the acute phase of COVID-19 infection reduced the incidence of long COVID by 41%. The new trial clarifies a crucial distinction: preventing long COVID and treating established long COVID appear to be different problems requiring different interventions. A drug that reduces risk when administered during acute infection does not appear to resolve symptoms that have already developed and persisted for months.
The finding reinforces how little is currently understood about the mechanisms sustaining long COVID once it is established, and underscores the ongoing need for trials targeting the immune dysregulation and other biological processes that appear to drive the syndrome.