Flu activity stays low as measles cases climb: the mid-September vaccine checklist for U.S. families

Flu surveillance remains quiet while the scheduling window opens

What CDC guidance says to book for fall

• Young children requiring two doses: Certain children ages 6 months through 8 years need two doses spaced at least four weeks apart. CDC advises administering the initial dose as soon as clinical supply arrives so the child can receive the second dose before influenza viruses circulate widely.
• Adults age 65 and older: CDC preferentially recommends three formulations for seniors: Fluzone High-Dose, Flublok Recombinant, and Fluad Adjuvanted. When none of these three enhanced options is in stock, clinicians administer any standard-dose age-appropriate flu vaccine.
• Transplant recipients ages 18 through 64: Individuals taking immunosuppressive medications following a solid organ transplant may receive high-dose or adjuvanted trivalent inactivated vaccines as acceptable options alongside standard-dose vaccines.
• General population ages 6 months through 64 years: CDC designates no single preferred product among approved inactivated, recombinant, or live attenuated vaccines. 3

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The pipeline and new research: what changes, and what stays the same

• Moderna mFLUSIVA: Moderna received U.S. FDA approval on August 5 for mFLUSIVA, an mRNA-based trivalent influenza vaccine for adults 50 and older. The agency granted accelerated approval for adults 65 and older based on antibody titers, with clinical-benefit confirmation studies ongoing. Moderna expects commercial availability during the 2026–27 season. The company announcement provides no local distributor lists, retail pricing, or insurance reimbursement schedules; consumers must verify pharmacy availability locally. 5
• Pfizer COVID-19 pipeline: Pfizer's scientific archive recorded no new respiratory vaccine approvals or public updates between September 7 and September 14. The latest U.S. regulatory milestone remains the August 27 FDA approval of the XFG-adapted COMIRNATY formulation for adults 65 and older and individuals ages 5 through 64 who possess qualifying medical conditions. 6
• Immune imprinting durability: On September 7, Immunity published a study by Zhang and colleagues examining antibody persistence in individuals sequentially exposed to SARS-CoV-1 and SARS-CoV-2 over a 20-year span (PMID 42705227). Approximately 60% of isolated antibodies targeted conserved structures from the original infection, while 37% recognized newer receptor-binding sites. The research clarifies long-term immune memory for future vaccine design, while everyday clinical eligibility for current COVID-19 boosters remains tied to existing FDA authorizations. 7
• Tonsillar responses to nasal flu vaccine: On September 13, Vaccine published an investigation by Hoen and colleagues examining immune dynamics in human palatine tonsils following live attenuated influenza vaccination (PMID 42732724). Children formed rapid germinal centers and class-switched antibodies within three days of vaccination, whereas adults expanded preexisting lymphoid structures gradually over time. The study provides biological evidence for strong pediatric mucosal immune activation, while supporting CDC's standing guidance that healthy children ages 2 and older may receive either injectable or nasal spray flu vaccines. 8

The mid-September household action checklist

1. Audit school immunization forms: Locate digital state registry entries or yellow immunization cards for school-age children. Ensure children have two documented MMR doses to protect against expanding community outbreaks.
2. Schedule childhood flu shots early: Confirm whether a child between 6 months and 8 years old needs two doses. If two doses are required, schedule the initial dose promptly to allow the required four-week interval before winter.
3. Book routine adult flu appointments: Select an appointment in September or October at a primary care clinic, workplace event, or local pharmacy. Any standard trivalent vaccine provides seasonal protection.
4. Request enhanced formulations for seniors: Adults 65 and older should ask their pharmacist or physician for Fluzone High-Dose, Flublok Recombinant, or Fluad Adjuvanted. If local supply is depleted, receive any available age-appropriate shot without delay.
5. Evaluate booster eligibility for high-risk members: Adults 65 and older and individuals ages 5 through 64 with chronic pulmonary, cardiovascular, or metabolic conditions should discuss the updated XFG-adapted COVID-19 vaccine with their provider.

This brief provides general health journalism for U.S. families. A physician, pharmacist, or local public health department can evaluate individual medical histories and confirm clinic-specific product availability.