Today in its weekly update, the Centers for Disease Control and Prevention (CDC) said there are 1,491 confirmed measles cases in the United States this year in 42 jurisdictions, an increase of 37 cases in the past week. 

Eighty-six percent of cases have been linked to one of 38 reported outbreaks, and roughly 12% of all case-patients have required hospitalization. 

Last year the country recorded only 285 measles cases, and 2025 has been the worst year for measles activity in the United States since the virus was officially declared to be eliminated in 2000. 

New case in Chicago area

In the Chicago area, Cook County has reported its second suburban case of measles this year, in an unvaccinated 4-year-old child who had traveled internationally and may have exposed others at O'Hare International Airport. So far Illinois has had 11 measles cases this year, compared with 67 for all of 2024.

This case is a serious reminder that vaccination is not just about individual protection, it’s a critical community responsibility

"This case is a serious reminder that vaccination is not just about individual protection, it’s a critical community responsibility," said Chicago Department of Public Health Commissioner Simbo Ige, MD, MPH. 

In Utah, wastewater surveillance has detected measles in samples from the Bear River Health District. State officials said wastewater sampling suggests at least one person with measles was in the area within the past week. 

Moderna yesterday announced promising preliminary immunogenicity data for its 2025-26 formulation of Spikevax COVID-19 vaccine, which targets the LP.8.1 variant.

In a press release, the company said the data are from an ongoing phase 4 clinical trial to gauge the safety, tolerability, and immune response to the updated Spikevax vaccine. The findings come ahead of a September 19 Centers for Disease Control and Prevention (CDC) meeting of the Advisory Committee on Immunization Practices, which is slated to discuss and vote on vaccine recommendations.

Spikevax prompted a greater than eight-fold increase in neutralizing antibodies against LP.8.1 in people ages 12 through 64 years with at least one underlying condition that puts them at high risk for severe COVID complications, as well as adults aged 65 and older.

Pfizer and BioNTech last week announced strong phase 3 clinical data for their updated COVID vaccine.

Safety profile consistent with earlier studies

Moderna said the safety profile is consistent with that of earlier studies, with findings revealing no new safety concerns.

Recent CDC data show that that wastewater SARS-CoV-2 detections are high and that LP.8.1 and related strains XFG and NB.1.8.1 continue to dominate. “This preliminary analysis confirms Moderna's updated COVID-19 vaccine is a strong match to today's top circulating strains in the U.S.,” the company said.

The latest clinical findings support preclinical data that supported the Food and Drug Administration (FDA) approval of the updated Spikevax formulation. 

An annual study published this week in Open Forum Infectious Diseases reveals the heavy burden and considerable costs of respiratory syncytial virus (RSV) infection in adults aged 75 years and older and high-risk people 65 to 74 years old in France.

Researchers at Hopital Pitie-Salpetriere and RSV vaccine manufacturer Moderna in Paris parsed data on RSV hospitalizations, including stays in the intensive care unit (ICU), on patients aged 65 and 74 with chronic respiratory disease or congestive heart failure and those 75 and older. Data were from the French National Hospital Discharge database. 

The study was conducted from 2017 to 2022, before approval of RSV vaccines in France. A correction factor derived from virologic data from two hospitals was used to adjust for underreporting.

"Hospitalizations are frequently underreported due to diagnostic challenges and a lack of standardized testing," the authors wrote.

True burden underreported

A total of 353 RSV hospitalizations occurred at two hospitals during the study period. Over half (54.1%) of patients were 65 and older, 52.1% were women, and 28.3% had at least one ICU stay.

The significant burden of RSV on adults aged 75+ and high-risk adults aged 65-74 with chronic conditions remains underreported.

Among adults aged 75 and older, the adjusted incidence of RSV hospitalization was 85 to 221 per 100,000 people, death rates among hospitalized patients were 8.9% to 10.4%, and annual adjusted costs were €27 million to €76 million ($32 million to $90 million US), mainly driven by ICU admissions. 

In total, 12.1% to 18.5% of patients in the older group were admitted to the ICU, and 33.5% to 37.7% were readmitted to the hospital within 3 months, mainly for respiratory (6.8% to 9.9%) or cardiorespiratory (11.3% to 16.0%) conditions.

Adults aged 65 to 74 also had higher adjusted rates of RSV infection (161 to 735 per 100,000 people), along with elevated rates of ICU admission and disproportionately higher costs due to intensive-care needs.

"The significant burden of RSV on adults aged 75+ and high-risk adults aged 65-74 with chronic conditions remains underreported," the researchers wrote. "Improved diagnostics and targeted vaccination programs are essential to reduce hospitalizations, mortality, and healthcare costs in these vulnerable groups."

• In its latest assessment of the public health threat from SARS-CoV-2, the World Health Organization (WHO) changed its risk level from high to moderate, though it noted that confidence in its assessment is low. The step-down in risk stems from declining hospitalizations and deaths since 2022 due to high population immunity and improved clinical management. The group added that most viruses are members of the Omicron JN.1 lineage, which has shown immune escape but not increased illness severity. It warned that a gap in surveillance data and genomic sequencing, especially from low- and middle-income countries, undermines a more accurate risk assessment. The WHO emphasized that COVID continues to circulate alongside other respiratory viruses and estimated that post-COVID symptoms occur in about 6% of people who have symptomatic infections. Low vaccine uptake amid continued virus evolution are other factors that contribute to risk-estimate uncertainty and required continued vigilance.
• The California Department of Public Health (CDPH) today announced its official respiratory virus immunization recommendations in accordance with its West Coast Health Alliance partners in Oregon, Washington, and Hawaii. In a statement, the CDPH said California Gov. Gavin Newsom this week signed a bill into law ensuring that the state’s vaccine recommendations are guided by evidence-based scientific recommendations from trusted medical groups such as the American Academy of Pediatrics, the American College of Obstetricians and Gynecologists, and the American Academy of Family Physicians. The law also ensures insurance coverage for vaccines and that pharmacists and other health professionals can continue to administer them.
• The Michigan Department of Agriculture and Rural Development (MDARD) today urged animal owners to remain vigilant and take steps to avoid the transmission of highly pathogenic avian flu from wild birds, given the start of wild bird migration and recently reported H5N1 outbreaks in poultry in North Dakota and South Dakota. So far, no recent outbreaks have been reported from Michigan. In related developments, the US Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) today reported two more H5N1 detections in poultry, both involving turkey farms in South Dakota—one in Beadle County and the other in McPherson County. Over the last 30 days, 10 outbreaks in commercial poultry and 5 in backyard flocks have led to the loss of about 500,000 birds.