This TWiV episode, recorded on April 4, 2025, features hosts Vincent Racaniello, Alan Dove, and Rich Condit discussing two primary scientific papers and current events impacting science and public health.
The first study examines the reverse zoonoses of 2009 H1N1 pandemic influenza A viruses and their evolution in U.S. swine. The hosts detail how the virus frequently transmits from humans to pigs (over 370 spillovers) and less often back to humans (17 times), leading to antigenic drift in pigs that could evade human vaccine-induced immunity. They highlight pigs as a significant "mixing bowl" for influenza viruses and stress the critical need for continued genomic surveillance in swine, expressing concern over current funding cuts to federal science agencies.
The second paper presents a natural experiment from Wales investigating the effect of Zostavax (shingles vaccine) on dementia incidence. By leveraging a unique birthdate-based vaccine eligibility cutoff, the study found that receiving the Zostavax vaccine significantly reduced the probability of developing dementia (20% relative reduction for vaccinated individuals). The discussion explores potential mechanisms, suggesting both a reduction in varicella-zoster virus (VZV) reactivation and an independent immunomodulatory effect of the vaccine. This finding offers compelling evidence for a link between herpes viruses and dementia, proposing a widely available and inexpensive intervention.
The episode also addresses listener questions, notably refuting misinformed claims by RFK Jr. regarding bird flu vaccines and discussing the dire consequences of proposed cuts to global health initiatives like the President's Malaria Initiative, underscoring the broader impact of politics on science and public well-being.
Summarizing TWiV 1207: Taking a Shot at Dementia
0:00 Introduction & Dedication: The episode opens with hosts Vincent Racaniello, Alan Dove, and Rich Condit, noting the passing of virologist Klaus Conzelmann, known for establishing reverse genetics for negative-strand RNA viruses.
9:41 Swine Flu: A Potential Pandemic Source: The first paper discusses reverse zoonoses of the 2009 H1N1 influenza A virus and its evolution in U.S. swine. Pigs are highlighted as a crucial "mixing bowl" for influenza viruses.
10:39 Frequent Human-to-Swine Spillovers: The study found 370 separate human-to-swine (H2S) spillovers of H1N1 from 2009-2021, driven by high flu burden in humans and close contact on pig farms.
11:43 Swine-to-Human Transmission: While less frequent, there were 17 swine-to-human (S2H) transmission events, some involving children, suggesting pigs can reintroduce antigenically drifted viruses to humans.
15:44 Antigenic Drift in Pigs: H1N1 viruses circulating in pigs show significant antigenic drift, with many maintaining persistence for over 10 years (similar to the 1918 lineage) and undergoing reassortment, potentially evading human immunity from current vaccines.
27:35 Impact of COVID-19: H2S spillovers reduced significantly during the 2020-2021 COVID-19 pandemic due to decreased human activity, but flu in pigs remained high, indicating internal circulation.
37:54 Importance of Surveillance: The hosts emphasize the critical need for continued genomic and antigenic surveillance of influenza in swine as part of pandemic planning, expressing concern over current funding cuts to federal science.
40:56 Zostavax Reduces Dementia Incidence: The second paper presents a "natural experiment" in Wales, where a birthdate cutoff (September 2, 1933) determined eligibility for the Zostavax shingles vaccine.
42:28 Robust Study Design: This unique cutoff created distinct eligible and ineligible cohorts, allowing for a strong comparison that largely bypasses confounding variables common in observational studies.
56:41 Significant Dementia Reduction: Being eligible for the vaccine reduced shingles incidence by 20%, and remarkably, reduced new dementia diagnoses by 8.5% for the eligible group and 20% for those actually vaccinated over seven years.
1:02:22 Proposed Mechanisms: The study suggests two potential mechanisms: reduction in VZV (varicella-zoster virus) reactivation (supported by higher dementia risk with multiple shingles episodes and reduced risk with antiviral treatment) and a general immunomodulatory effect of the vaccine.
1:11:00 Implications for Public Health: The findings provide strong evidence linking herpes virus reactivation to dementia and suggest a simple, inexpensive intervention (shingles vaccination) could significantly reduce dementia rates. The hosts recommend continuing with the newer, more effective Shingrix vaccine.
1:18:12 Listener Mail - RFK Jr. on Bird Flu: Michael raises concerns about RFK Jr.'s comments on bird flu vaccines, which suggest vaccines create "mutant factories" and advocate for "letting the virus run through the flock." The hosts strongly refute these claims, highlighting his misunderstanding of immunology, chicken farming, and public health.
1:26:35 President's Malaria Initiative Cuts: Brian shares a disturbing account of the severe impact of proposed cuts to the President's Malaria Initiative by the current administration, linking it to Elon Musk's alleged influence and potential for thousands of preventable deaths in Africa.
Rich: "Certain Roller Coasters May Help Small Kidney Stones Pass" – research showing that rides like Thunder Mountain can help dislodge kidney stones.
Alan: Analog Science Fiction and Fact and Asimov's Science Fiction magazines – two long-standing sci-fi publications, available digitally.
Vincent: "Science Under Threat in the United States: How scientists and institutions should respond" (Elife) – an article urging scientists to engage with the public and policymakers to defend science funding and integrity.
1:43:03 Listener Pick: "Why Techdirt Is Now A Democracy Blog" – an article discussing how political interference increasingly intertwines with technology and scientific issues, mirroring MicrobeTV's own experiences.