Issue 1868: April 8, 2026

RSV preventive antibody products, nirsevimab (Beyfortus, Sanofi) and clesrovimab (Enflonsia, Merck), are routinely recommended from October through March in most of the contiguous United States. This season, data from the National Respiratory and Enteric Viruses Surveillance System demonstrates a late RSV season, with elevated RSV activity persisting into April in some regions. CDC encourages jurisdictions to review local data and consider extending administration beyond March, particularly for newborns. 

The Association of Immunization Managers (AIM) is collecting information on changes in recommendations for use of RSV preventive antibody products from the 66 federally funded immunization program jurisdictions (including states, certain cities or counties, and territories). On April 2, AIM publicly posted a map showing current RSV preventive antibody guidance, based on available information. As of April 1, 48 jurisdictions extended their RSV preventive antibody administration season through April 30. Rhode Island and Philadelphia extended through April 15 and will reassess the situation. Two jurisdictions remain undecided and four opted not to extend, although Virginia and Missouri will consider requests by VFC program participants to extend antibody administration for their patients on a case-by-case basis. Ten jurisdictions maintain year-round RSV preventive antibody administration policies due to the year-round circulation of the virus in their areas.

Visit the color-coded map for each jurisdiction's status on AIM's website for details on your jurisdiction. 



Related Links

• AAP: RSV Immunization Administration Frequently Asked Questions web page
• Immunize.org: Standing Orders for Administering Nirsevimab RSV Preventive Antibody (Beyfortus, by Sanofi) to Infants and High-Risk Young Children (PDF)
• Immunize.org: Standing Orders for Administering Clesrovimab RSV Preventive Antibody (Enflonsia, by Merck) to Infants (PDF)
• Immunize.org: Vaccines A–Z: RSV (Respiratory Syncytial Virus) main page
• Association of Immunization Managers: Immunization Program Directory web page

As of April 2, CDC reports 1,671 confirmed measles cases in the first quarter of 2026. In comparison, throughout 2025, 2,286 measles cases were reported in the United States. So far, 32 states reported measles cases in 2026.

• The Montana Department of Public Health and Human Services confirmed five cases of measles in Lewis and Clark County after a recent measles exposure at St. Peter’s Health emergency department
• The Michigan Department of Health and Human Services issued updated recommendations on April 2 for accelerated MMR vaccination of infants age 6 through 11 months residing in or traveling to certain counties with ongoing measles transmission
• Utah reports 362 cases in 2026, with 142 occurring in the past 3 weeks
• South Carolina confirmed 997 measles cases since its outbreak began in October 2025
• The Florida Department of Health confirmed 145 cases in 2026 as of March 28

CDC only requires reporting of laboratory-confirmed measles cases. Cases without laboratory testing for confirmation are not included in these numbers. Actual numbers of cases are, therefore, higher than confirmed case counts.

A chart of cumulative measles cases reported in states with the largest outbreaks since the beginning of 2025, as of March, from the Johns Hopkins International Vaccine Access Center, appears below. The chart underscores the rapid pace of measles transmission and the recent surge in cases in Utah.
 

Immunize.org offers measles-related resources for the public on several of our affiliated websites:

• VaccineInformation.org: Measles web page
• LetsGetRealAboutVaccines.org: Measles web page
• Immunize.org: Vaccines A–Z: Measles main page

Related Links

• AAP: Fact Checked: The MMR (Measles, Mumps and Rubella) Vaccine Is Safe and Effective web page
• CDC: Measles Cases and Outbreaks main page
• Common Health Coalition: More Illness, Greater Cost: Spotlight Brief; Childhood Immunizations (PDF)
• Johns Hopkins International Vaccine Access Center: U.S. Measles Tracker web page
• PopHIVE (Yale School of Public Health): Infectious Diseases Dashboard: Measles web page
• Health Canada: Measles and Rubella Weekly Monitoring Report
• Immunize.org: Vaccines A–Z: Measles main page

Nationwide respiratory virus activity reported by CDC is highlighted below.

• Influenza (data through March 28):
  • Influenza A activity is low across all regions while the amount of and trends in influenza B activity vary by region, with influenza B dominating late-season activity
  • Since October 1, 2025, there have been 30–54 million illnesses, 370,000–770,000 hospitalizations, and 23,000–76,000 deaths from flu so far this season according to CDC estimates
  • Deaths of four more children were reported during week 12, for a total of 127 child deaths with influenza reported so far this season
• RSV:
  • Respiratory Illnesses Data Channel states that RSV activity started later than expected in most regions, and higher levels of RSV activity continue into April
  • Consult state public health authorities for guidance on how long to continue administering RSV preventive antibody products to infants as the RSV season persists
• COVID-19: Activity is decreasing nationally 

Level of Respiratory Illness Activity
The ILI map is shown below.

Vaccination against COVID-19, influenza, and RSV reduces the risk of severe illness and should continue as long as disease is circulating locally. Immunization of eligible infants against RSV is crucial while RSV is circulating. Follow guidance of public health officials for RSV immunization recommendations.