Experts considered the 2024-25 influenza season severe, the most serious since the 2017-18 season. Vaccination against flu protected US adults and children from hospitalization and needing outpatient medical care, according to a paper published last week in Open Forum Infectious Diseases. 

“These findings support influenza vaccination as an important tool to reduce influenza-associated morbidity and mortality across the lifespan,” wrote the authors, led by researchers at the Centers for Disease Control and Prevention (CDC).

43% to 54% vaccine effectiveness

Using a test-negative, case-control design, scientists examined the electronic records of patients who visited one of seven Virtual SARS-CoV-2, Influenza, and Other (VISION) sites to understand how well the flu vaccine prevented hospitalizations and emergency department and urgent care clinics (ED/UC) from October 2024 to April 2025. They looked at healthcare interactions in children ages 6 months to 17 years, as well as adults. 

The data included 5,764 pediatric hospitalizations and 102,854 ED/UC visits. Among adults, 76,072 were hospitalized, and 233,411 sought outpatient treatment. 

In total, 17% of children and 28.2% of adults were vaccinated. For children, the vaccine was 51% effective against flu-related hospital stays and 54% effective against ED/UC visits. Vaccine effectiveness in adults was 43% against hospitalization and 49% against ED/UC visits. 

These findings support influenza vaccination as an important tool to reduce influenza-associated morbidity and mortality across the lifespan.

The researchers found that vaccines were most effective during the first two months following vaccination, after which protection waned. 

“Seasonal influenza vaccination provided protection against influenza-associated hospitalizations and ED/UC encounters among US children and adults during the 2024-25 season,” the authors wrote. “Protection was also observed against critical illness, including ICU [intensive care unit] admissions in children and ICU admissions and deaths in adults.”  

Of 1,141 adult patients in Arizona hospitalized for community-acquired pneumonia, 76% were tested for Coccidioides infection, and 10% had positive results, Mayo Clinic Phoenix researchers report in Open Forum Infectious Diseases.

The researchers reviewed the medical records of CAP patients admitted to Mayo Clinic Hospital from November 2024 through October 2025 to determine the rate and patterns of coccidioidomycosis testing and positivity over time.

The fungal infection coccidioidomycosis (valley fever) is endemic to the southwestern United States, Washington state, and Central and South America. It accounts for 15% to 30% of CAP in endemic areas such as Arizona. 

Common symptoms include fever, cough, shortness of breath, rash, chest pain, weight loss, and fatigue. But these symptoms are often absent or similar to those of other CAP-causing pathogens, often slowing diagnosis and treatment. Even otherwise healthy patients can develop severe disease.

“Although the Centers for Disease Control and Prevention (CDC) report 10,000 to 20,000 coccidioidomycosis cases annually, the true incidence is likely much higher because of (1) state-based differences in reporting practices and (2) probable missed diagnoses,” the authors wrote.

Call for universal testing

Coccidioides was the most commonly identified pathogen in CAP patients. Positive testing rates were highest in November and December 2024 and October 2025 (range, 13% to 21%) and in March 2025 (15%), consistent with the disease’s seasonal variation. 

A shorter LOS could be an institutional incentive to test all patients with CAP for coccidioidal infection.

Most patients were tested if they had concerning chest radiographs, fatigue, fever, and/or shortness of breath. Those with a history of coccidioidomycosis and those with rash, night sweats, headache, or high white blood-cell count were most likely to test positive.

The authors called for testing all CAP patients for Coccidioides. When Coccidioides was identified early, hospital length of stay (LOS) was shorter than that with noncoccidioidal CAP.

“A shorter LOS could be an institutional incentive to test all patients with CAP for coccidioidal infection,” they wrote. “Missed diagnoses can potentially prolong symptoms and hospitalization, as well as unnecessarily exposing patients to antibacterial therapy or invasive diagnostic testing that may contribute to patient anxiety.”

Administering the monoclonal antibody nirsevimab to infants in primary care reduced outpatient antibiotic prescribing for respiratory infections, according to a study by researchers with the Children's Hospital of Philadelphia (CHOP).

Respiratory syncytial virus (RSV) is the most common cause of hospitalization in children younger than 1 year old and is estimated to be responsible for one out of every three hospitalizations for acute respiratory tract infection (ARTI). It's also a common reason for antibiotic use: Roughly half of children hospitalized with RSV, and nearly one-third of those who show up at outpatient clinics with RSV, receive an antibiotic.

Approved by the Food and Drug Administration in 2023, nirsevimab (Beyfortus) provides infants with immediate, short-term protection against RSV and has been shown to prevent RSV-associated hospitalizations. To evaluate its effectiveness in reducing antibiotic use for ARTIs, the researchers analyzed electronic health record data from 32 practices in the CHOP Primary Care Network. Using target trial emulation, they compared outpatient and inpatient antibiotic prescribing in infants younger than 8 months with ARTIs who received nirsevimab with those who didn't.

“Because (1) ARTIs are the most common indication for sick visits in infants, (2) antibiotic prescribing for viral ARTIs, including those caused by RSV, is common, and (3) RSV infections can either mimic or lead to bacterial illnesses (eg, acute otitis media [ear infection] and pneumonia), nirsevimab use might indirectly reduce safely avoidable antibiotic exposure in this population,” the study authors wrote last week in Clinical Infectious Diseases.

14% reduction in outpatient antibiotics for ARTIs

Among the 15,341 infants (average age, 3.5 month; 48.7% female) who were eligible for inclusion, 7,413 received nirsevimab; both groups were similar in terms of measured characteristics, including gestational age, complex chronic conditions, and insurance coverage. Compared with no treatment, nirsevimab administration led to a 14.4% reduction in antibiotic prescribing for outpatient ARTIs, a 40.3% reduction in antibiotics for outpatient bronchiolitis, and 69.4% reduction in antibiotics for RSV-related hospitalizations.

"Although the primary purpose of nirsevimab is to prevent RSV-associated hospitalizations, this study demonstrates a clinically meaningful reduction in RSV-associated antibiotic use, revealing the additional impact of nirsevimab as an important tool for antibiotic stewardship," the authors wrote.