Top 5 Infectious Disease News stories Week of May 31-June 7

FDA Approves Moderna’s COVID-19 Vaccine

The FDA has approved Moderna’s new COVID-19 vaccine, mRNA-1283 (mNEXSPIKE), marking the first authorization under updated federal guidelines that prioritize vaccination for adults 65 and older and individuals aged 12–64 with CDC-defined risk factors. In a Phase 3 trial of over 11,000 participants, mRNA-1283 demonstrated a 9.3% higher relative vaccine efficacy compared to Moderna’s original vaccine (mRNA-1273), with a 13.5% increase in efficacy among adults 65 and older. The vaccine also showed a comparable safety profile with fewer local side effects. Moderna plans to make mRNA-1283 available for the 2025-2026 respiratory virus season in the U.S. Meanwhile, COVID-19 vaccination remains available for children 6 months and older through shared clinical decision-making, reflecting ongoing federal adjustments to immunization recommendations.

Rethinking Fungal Blood Cultures in Sepsis Workups

A recent retrospective study from UF Health Shands Hospital, presented by Logan Brock, PharmD, at MAD-ID 2025, questions the routine use of fungal blood cultures during sepsis workups, finding they rarely provide additional diagnostic value beyond standard blood cultures and take significantly longer to yield results. Reviewing over 2,000 inpatient cases, fungal cultures showed growth in very few instances not detected by standard cultures, with Candida species predominating. Although fungal cultures had limited overall utility, they were crucial in select high-risk cases, such as a patient with bowel perforation where fungal culture results guided effective antifungal therapy. The study suggests fungal blood cultures should be reserved for targeted use rather than ordered routinely in sepsis evaluations.

Vowst Maintains Consistent Safety Profile in rCDI Patients with Comorbidities

At the 2025 MAD-ID meeting, Dianne Nguyen, MD, presented an integrated analysis of two Phase 3 trials demonstrating that Vowst™ (fecal microbiota spores, live–brpk), a microbiome therapy for preventing recurrent Clostridioides difficile infection (rCDI), maintains a consistent and favorable safety profile even in adults with significant comorbidities such as renal impairment, diabetes, cardiac disease, and immunocompromised status. Among 349 treated patients, adverse event rates were comparable or lower than those seen in placebo groups, with no serious adverse events attributed to VOWST and no treatment-related discontinuations. Nguyen highlighted ongoing real-world studies to further evaluate Vowst’s tolerability and effectiveness in these high-risk populations, supporting its potential broader use in routine clinical practice.

Reviewing the Efficacy and Safety of Omadacycline in Immunocompromised Patients

A new real-world observational study presented at MAD-ID found that omadacycline achieved an 86% clinical success rate in treating a variety of infections among immunocompromised patients, including those with solid organ transplants, chemotherapy, or immune-suppressing medications. The study involved 22 adults with common infections such as respiratory, intra-abdominal, skin and soft tissue, and bone/joint infections caused by pathogens like Enterococcus faecium and MRSA. Omadacycline was well tolerated, with only mild gastrointestinal side effects reported and no treatment discontinuations or deaths within 30 days. Investigators highlighted the antibiotic’s value as an effective oral option with fewer toxicities than alternatives like linezolid, especially for long-term use in this vulnerable population, though they noted the need for larger studies to confirm these findings.

Ceftolozane/Tazobactam Shows Strong Activity Against ESBL E coli, But Gaps Remain for K pneumoniae

A study presented at MAD-ID by Jose Alexander, MD, evaluated the in vitro activity of ceftolozane/tazobactam (C/T) against ESBL-producing bacteria from clinical samples, focusing on Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis. The analysis of 125 isolates showed that 98% of ESBL E coli were susceptible to C/T, supporting its use as an empiric treatment for these infections. Although, only 76% of K pneumoniae isolates were susceptible, indicating a significant resistance gap and highlighting the need for species-specific susceptibility testing before using C/T for K pneumoniae infections. All five P mirabilis isolates were susceptible, though the sample was small. The findings emphasize cautious use of C/T in ESBL infections, particularly for K pneumoniae, and call for further research correlating lab susceptibility with clinical outcomes.