Interim estimates for how well this year's flu vaccines protected against medically attended flulike illness showed moderate vaccine effectiveness (VE) overall, with higher levels in children than in adults, researchers from the Centers for Disease Control and Prevention (CDC) and their state health partners reported today in the latest edition of Morbidity and Mortality Weekly Report (MMWR).

The data come from four networks that the CDC uses to track vaccine effectiveness, which cover patients in 22 states. This is the first year that pediatric and adult VE estimates from the four networks have been presented together. The study did not measure how VE waned after vaccination.

For adults, VE against flu diagnosed in outpatient settings ranged from 33% to 49% and against flu hospitalization ranged from 41% to 44%. For the pediatric age-group, VE for flu detected in outpatient settings was 59% to 67% and against flu-linked hospitalization was 52% to 61%. "These findings demonstrate that the 2023–24 seasonal influenza vaccine is effective at reducing the risk for medically attended influenza virus infection," the group wrote, noting that the interim results were consistent with findings from previous years.

The vaccines were effective against both influenza A, which has mainly been the 2009 H1N1 strain this season, and influenza B, similar to recent estimates from Canada and Europe. For seniors, a group at higher risk for flu complications, VE was similar to adults ages 18 to 64 years old.

The CDC noted that flu vaccine coverage has been lower this season than last season and is even lower than prepandemic uptake.

California estimate also finds moderate protection

In a separate report in the same MMWR issue, an analysis of surveillance data from California found that flu vaccines so far this season have provided moderate protection against lab-confirmed flu across all age-groups.

Overall, VE was 45%, highest in children younger than 18 years old. VE declined with age and was 30% in adults ages 65 and older.

A Chinese study published yesterday in PLOS One finds that more than half of the isolates from pet dogs diarrhea contained multidrug-resistant (MDR) Escherichia coli, which the researchers say may pose a threat to both animal and human health.

Researchers from Sichuan Agricultural University evaluated the presence of antimicrobial resistance (AMR) in 135 E coli isolates from the dogs using the disc-diffusion method. They also screened for antibiotic resistance genes (ARGs), virulence-associated genes (VAGs), and population structure using polymerase chain reaction (PCR) for 74 MDR strains and analyzed the link between AMRs and ARGs or VAGs.

Minimizing MDR E coli spread from pets to people

Of the 135 isolates, 54.8% were identified as MDR E coli, 71.1% were highly resistant to ampicillin, 62.2% were resistant to tetracycline, and 59.3% were resistant to trimethoprim-sulfamethoxazole. Twelve ARGs in six categories and 14 VAGs in four categories were observed in the 74 MDR strains, with fimC (100%) and tetA (96.0%) the most prevalent.

The widespread use of antibiotics has significantly caused the increase of MDR E. coli which were isolated from companion animals.

The analysis of associations between ARGs and AMRs or VAGs in MDR strains showed 23 significant positively associated pairs between ARGs and AMRs, while only 5 associated pairs were seen between ARGs and VAGs (3 positively and 2 negatively associated pairs).

"The widespread use of antibiotics has significantly caused the increase of MDR E. coli which were isolated from companion animals," the study authors wrote. "Measures should be taken to prevent the transmission of MDR E. coli between companion animals and humans, as the fecal shedding of MDR E. coli from pet dogs may pose a threat to humans."

They called for future research with more samples and expanded sampling areas and the use of high-throughput or whole-genome sequencing to provide more comprehensive data on MDR E coli strains from dogs with diarrhea.

Pfizer today announced that its respiratory syncytial virus (RSV) vaccine Abrysvo maintained high efficacy in the second season after vaccination in adults ages 60 and older, according to the latest data from an ongoing phase 3 clinical trial.

In a press release, the company said vaccine efficacy against RSV-related lower respiratory tract disease, defined by three or more symptoms, after season two was 77.8% (95.0% confidence interval [CI], 51.4% to 91.1%). For comparison, vaccine efficacy after season one was 88.9% (95% CI, 53.6% to 98.7%).

Efficacy was consistent across the seasons for both RSV A and RSV B strains. Researchers also saw sustained efficacy against less severe symptoms: 65.1% after season one and 55.7% after season two. No new adverse events were reported through the second season.

Durable protection against 2 strains

Annaliesa Anderson, PhD, senior vice president and chief scientific officer of vaccine research and development at Pfizer, said the company is encouraged by the level of protection after two full RSV seasons. "This new data indicate that broad and durable protection against both types of RSV that cause disease, RSV A and RSV B, is the potential benefit to having a bivalent vaccine."

Broad and durable protection against both types of RSV that cause disease, RSV A and RSV B, is the potential benefit to having a bivalent vaccine.

The company said it will submit the data to regulatory authorities and vaccine technical committees and will publish the findings in a peer-reviewed scientific journal.

In the United States, the Food and Drug Administration (FDA) approved Abrysvo for people ages 60 and older in May 2023, and the following month the Centers for Disease Control and Prevention recommended Abrysvo and the RSV vaccine made by GSK (Arexvy) for adults ages 60 and older based on shared clinical decision making with health providers. In September, the CDC recommended that pregnant women receive Abrysvo as a strategy to protect newborns from RSV.