This episode of TWIV (This Week in Virology) discusses various infectious disease topics, including ongoing challenges with fungal infections, policy issues surrounding COVID-19 vaccines, updates on Legionella and avian influenza, and the persistent threat of measles and seasonal flu. Key discussions include the political interference impacting COVID-19 vaccine recommendations and mandates in the US, particularly Florida's controversial stance. The hosts review new data on the cardiovascular benefits of flu vaccination, the disappointing low uptake of RSV immunization in infants, and the potential, albeit limited, role of nasal sprays and metformin in COVID-19 prevention and post-COVID condition management. Listener questions cover practical advice on COVID-19 vaccine choices, post-infection vaccination timing, and the implications of immunosuppressive therapies on COVID-19 severity.
TWIV 1250: Navigating Infectious Disease in a Changing World
0:30 Fungal Pathogens & Global Distribution: The episode opens with a discussion on medically relevant fungi, including Aspergillus (aspergillosis), Coccidioides (coccidioidomycosis/desert fever), Histoplasma (histoplasmosis), and Cryptococcus gadi. Dr. Griffin highlights that fungal diseases like histoplasmosis are more globally distributed than commonly perceived, leading to missed or delayed diagnoses. Immunosuppression is a key factor in disseminated fungal infections.
3:38 The "Race Between Education and Catastrophe": A sobering quote sets the stage for discussing the growing disregard for scientific expertise, exemplified by recent anti-expert sentiments, particularly concerning public health.
4:08 COVID-19 Vaccine Access & Political Interference:
Pharmacy Barriers (4:08): CVS and Walgreens initially required prescriptions for new COVID-19 vaccines in many states due to the CDC's Advisory Committee on Immunization Practices (ACIP) not yet formally recommending them, despite FDA approval. Some states, like Colorado, intervened to allow pharmacists to administer them.
ACIP Meeting Delays (7:03): An upcoming ACIP meeting (Sept 18/19, 2025) was crucial for formal recommendations, but faced calls for postponement from Senator Bill Cassidy, citing "serious allegations" and "turmoil" in CDC leadership. Concerns are raised about new panel members proposed by Kennedy, who are largely vaccine critics lacking immunology expertise.
9:36 Florida's Anti-Vaccine Stance: Florida's Surgeon General Ladapo and Governor DeSantis announced plans to end all school-age vaccine mandates, promoting "personal freedom" over public health. The hosts strongly condemn this as a dangerous ideological stance that will harm vulnerable populations, including infants and immunocompromised individuals, by eroding community immunity.
14:26 Legionella Outbreak Update: As of August 29th, 2025, a Legionella outbreak had 114 confirmed cases, 90 hospitalizations, and 7 deaths. Optimism is expressed that mitigation efforts have contained the source, as Legionella spreads via contaminated water vapor, not person-to-person.
15:57 H5N1 Avian Influenza Case: An MMWR report details a school-aged child in San Francisco infected with highly pathogenic avian influenza A H5N1 (Dec 2024-Jan 2025). No known animal exposure or human-to-human transmission was identified, though the family purchased raw poultry from a live bird market two weeks prior. The reporting delay (case from a year ago) is noted.
19:17 Ongoing Measles Cases: As of September 2nd, 2025, the US reported 1,431 confirmed measles cases. 92% of cases were in unvaccinated individuals, and 12% required hospitalization due to illness severity. Canada also reported a significant number of ongoing cases (4,799 total, 82 new in Week 34).
21:20 Flu Season & Cardiovascular Benefits of Vaccination:
Pediatric Deaths: 278 pediatric deaths from flu occurred last season.
ACIP Recommendations (22:02): The ACIP recommends routine annual flu vaccination for all individuals aged 6 months and older without contraindications.
Heart Health (23:04): Studies show flu vaccination significantly reduces the risk of myocarditis, pericarditis, and other cardiovascular events. A high-dose flu vaccine was found to be 45.71% more effective in reducing myocarditis/pericarditis risk. Vaccinating acute heart failure patients in hospital reduced all-cause mortality or readmission by 17% over 12 months, highlighting flu's inflammatory impact on cardiovascular health.
27:29 Low RSV Immunization Coverage: Despite new tools like Nirsevimab monoclonal antibody for infants and maternal RSV vaccines, only 29% of US infants were immunized against RSV (Oct 2023-Mar 2024 season). Uptake varied greatly by state, with Florida, Nevada, Mississippi, and Oklahoma showing very low rates. Reasons include supply issues and lack of provider education, leading to preventable infant hospitalizations.
Rising Cases (31:30): COVID-19 cases are currently rising across the US, with a predicted winter peak.
Maternal Antibodies (32:41): SARS-CoV-2 mRNA vaccination during postpartum elicits robust antibodies in breast milk, with neutralization capacity, though its direct protective effect on infants needs further study.
Interferon alpha nasal spray showed a 40% reduced risk of COVID-19 in cancer patients but no effect on other respiratory viruses.
Azelastine (an antihistamine) nasal spray showed a ~70% reduction in COVID-19 infections in a small Phase 2 trial, but the low number of cases means it's not yet recommended for general use.
40:53 Metformin & Post-COVID Conditions (PCC): A large UK retrospective study found that overweight/obese individuals who started metformin within 3 months of a COVID-19 diagnosis had a 12.58% lower one-year risk of PCC (defined by symptoms). This observational finding suggests a modest benefit, though it is less significant than the impact of antivirals like Paxlovid during acute infection, which the UK regrettably underutilizes.
47:39 Acute COVID Treatment Recommendations: Current recommendations for the early viral phase (first week) include Paxlovid, Remdesivir, Molnupiravir, and convalescent plasma. For progressing disease (second week, hospitalization), treatments involve steroids, anticoagulation, pulmonary support, Remdesivir, and immune modulation.
Moderna Vaccines: Moderna's "Next Spike" (next-gen) uses a shorter spike protein code and lower mRNA dose, potentially reducing side effects, but its long-term durability is a concern.
Vaccination Timing: Waiting 3 months after a COVID-19 infection to vaccinate is generally fine; 6 months is recommended between doses for those 65 and older.
Flu Vaccine & Egg Allergy: Current CDC guidance clarifies that egg allergy is not a contraindication for flu vaccination, despite outdated package inserts.
Novavax Primary Series: For COVID-naive individuals, a prime-boost (initial shot followed by a booster at 3 months) is still recommended.
Immunosuppressants: Patients on TNF inhibitors (e.g., Symponi) may have a decreased risk of severe COVID-19 due to the suppression of cytokine storms.
COVID Vaccine Timing: While traditionally in October, the current rising wave makes timing tricky due to potential waning immunity.