In this clinical update from "This Week in Virology," Dr. Daniel Griffin and Vincent Racaniello discuss several key topics in virology and public health. A central focus is a groundbreaking paper in Nature demonstrating that SARS-CoV-2 mRNA vaccines can sensitize tumors to immune checkpoint inhibitor (ICI) cancer therapies, significantly improving patient survival by boosting a Type I interferon response. They also analyze a meta-analysis linking various viral infections, including influenza, SARS-CoV-2, and HIV, to a substantially increased risk of cardiovascular events like heart attacks and strokes. The episode provides an update on the fall 2025 vaccine landscape, reviewing the effectiveness of current vaccines for COVID-19, RSV, and influenza. Public health updates include rising measles cases that threaten the elimination status in the US and Canada, ongoing H5N1 avian flu outbreaks in US poultry, and the beginning of the RSV season. The discussion concludes with a Q&A session addressing listener questions on newborn vaccination, schistosomiasis risk, foot-and-mouth disease, and the benefits of the Shingrix vaccine.
TWiV 1266 Clinical Update: mRNA Vaccines, Viral Risks, and Seasonal Outlook
5:21 mRNA Vaccines Boost Cancer Immunotherapy: A major study published in Nature shows that receiving a COVID-19 mRNA vaccine within 100 days of starting immune checkpoint inhibitor (ICI) therapy significantly enhances treatment effectiveness.
Key Finding: The study found that vaccination nearly doubled the three-year survival rate for certain cancer patients (from ~30% to ~60%).
Mechanism: The vaccine triggers a strong Type I interferon response, which activates the immune system to better recognize and attack cancer cells. It also increases PD-L1 expression on tumors, making them more susceptible to ICI drugs.
Takeaway: This suggests that off-the-shelf mRNA vaccines, not specific to cancer, can act as potent immune modulators to improve cancer treatment outcomes.
16:11 Viral Infections Linked to Increased Cardiovascular Risk: A systematic review and meta-analysis from the Journal of the American Heart Association confirms a strong link between viral infections and subsequent cardiovascular diseases.
Key Data:
Influenza: Linked to a 4-fold increased risk of acute myocardial infarction and a 5-fold increased risk of stroke within the first month post-infection.
SARS-CoV-2: Associated with an approximately 1.7-fold increased risk of both coronary heart disease and stroke.
Chronic Viruses: HIV, Hepatitis C, and Herpes Zoster (shingles) also show a persistent, long-term elevated risk.
Takeaway: This highlights a critical benefit of vaccination: preventing the initial viral infection also reduces the significant risk of associated heart attacks and strokes.
19:22 Fall 2025 Vaccine Effectiveness Update: A meta-analysis published in the New England Journal of Medicine provides effectiveness data for the current season's vaccines.
COVID-19 (XBB.1.5 based): ~46-50% effective against hospitalization. The risk of vaccine-associated myocarditis remains very low (1.3-3.1 per 100,000 doses in male adolescents) and is far less severe than myocarditis from COVID-19 infection.
RSV: Vaccines show 68% or more effectiveness against hospitalization in older adults. A risk of Guillain-Barré syndrome is noted (18.2 excess cases per million doses).
Influenza: 48% effective against hospitalization in adults and 67% in children.
23:34 H5N1 "Bird Flu" Spreading in US Poultry: The USDA reports continued detections of highly pathogenic avian influenza (HPAI) in commercial and backyard flocks across the United States.
Details: Major outbreaks have been confirmed in large commercial turkey farms in Minnesota, affecting hundreds of thousands of birds. Millions of birds have been affected nationwide since the outbreak began.
Cause: The spread is largely attributed to migrating wild birds.
26:08 Measles Outbreak Worsens: The US has recorded 1,648 confirmed measles cases as of late October 2025, an increase of 30 cases in one week.
Key Takeaway: Due to the sustained transmission, both the United States and Canada are on track to lose their official "measles elimination" status in the coming months.
28:13 RSV Season Begins with New Vaccine Data: RSV activity is beginning to increase, particularly in southern states like Florida.
Details: Studies on the newest RSV vaccines show positive results. Revaccination with the Moderna mRNA vaccine at 12 months effectively boosts antibody levels. A UK study of the protein-based Pfizer vaccine (Abrysvo) in adults 75-79 found it was over 82% effective at preventing hospitalization.
33:00 COVID-19 Vaccine Durability: An observational study of US veterans showed that the 2024-2025 COVID-19 vaccine was 64% effective against death at 6 months. Another study showed protection against hospitalization/death waned from 57% at 4 weeks to 34% at 20 weeks, but protection against severe outcomes remains more durable than protection against infection.
Hepatitis B vaccine in newborns: Newborns have a sufficiently competent immune system to mount a protective response.
Risk of Schistosomiasis (Malawi): With minimal water contact, the infection risk is very low. Taking the prescribed preventative Praziquantel is a simple, low-risk option compared to extensive testing.
Foot-and-Mouth Disease from Argentine Beef: Argentina is certified free of the disease; concerns are likely economic rather than a public health risk.
Shingrix Vaccine: Given the link between shingles and dementia, and a family history of Alzheimer's, getting the highly effective Shingrix vaccine is a reasonable choice, as the benefit of preventing shingles and its complications likely outweighs the risk of a temporary injection site reaction.