Four measles-associated deaths in Pennsylvania, and flu positivity at 2.7%: this week's plan (2026)

Flu season is now visible in the numbers. Of 39,788 respiratory specimens tested by clinical laboratories nationwide during the week ending September 19, 1,085 came back positive for influenza — 2.7%, up from 1.8% the week before and 1.3% the week before that. 1

Measles produced a harder piece of news. CDC's national page, updated September 25, lists one confirmed measles death for 2026 — the first time this year's page has carried one — while Pennsylvania's health department has confirmed four measles-associated deaths in the state's outbreak. 2 3

A household's to-do list looks the same as it did a month ago: a flu shot for everyone 6 months and older, and two documented MMR doses for everyone who can receive them. What changed is the standing of the second item. A measles record gap used to be a bet against the odds. It is now a bet against an outbreak that has killed people.

Flu tests are turning positive faster

CDC published its Week 37 report on September 25, covering the week ending September 19. Clinical laboratories tested 39,788 specimens and found influenza in 1,085, a positivity rate of 2.7%. Labs also ran more tests than the week before, and a larger share of them came back positive: the positivity rate has climbed three weeks running, from 1.3% to 1.8% to 2.7%. 1

Public health laboratories confirmed 131 positives and subtyped 96 of them: 91 were influenza A(H1N1)pdm09 and five were A(H3N2), so early-season circulation is running heavily toward one of the two influenza A components the vaccine covers. No specimen contained H5 avian influenza, and no new human infection with a novel influenza virus was reported. 1

Outpatient clinics recorded fever with a cough or sore throat in 1.6% of visits; among children ages 0 through 4 the share was 5.2%. Emergency departments logged a flu discharge diagnosis in 0.3% of visits. Fifty-five jurisdictions reported minimal respiratory activity, none reported low, moderate, high, or very high, and of the core-based statistical areas reporting, 669 showed minimal activity and six showed moderate. 1

Hospitals reported 1,991 laboratory-confirmed flu admissions during the week, or 0.6 per 100,000 people, with the highest rate among adults 65 and older at 2.1. Laboratory-confirmed flu hospitalizations since October 1 reached 31,363. Deaths from influenza made up 0.06% of all deaths that occurred in the week ending September 19. 1

Three influenza-associated pediatric deaths were reported during the week, and all three occurred earlier. Two fell inside the 2025–26 season, in the weeks ending December 13, 2025, and January 3, 2026, bringing that season's reported total to 195 children. The third occurred in February 2025, in the 2024–25 season, which now stands at 298. Late reports arrive for months after a season closes, so a February death surfacing in a September report is a revision of an old total rather than a new event. 1

Four measles-associated deaths in Pennsylvania

CDC updated its measles page on September 25 with figures reported through September 24 at noon. The United States has recorded 3,659 confirmed cases in 2026, reported by 47 jurisdictions, plus 17 cases among international visitors. The year has produced 40 outbreaks, and 95% of cases, or 3,478, are outbreak-associated. Hospitalizations reached 327, equal to 9% of confirmed cases, including 14% of cases in children under 5 and 12% of cases in adults 20 and older. Where vaccination status was documented, 95% of patients were unvaccinated or had no record of a dose. 2

Cases remain concentrated in a handful of states: Pennsylvania has reported 850, South Carolina 670, Utah 535, Texas 192, and Virginia 178. The national weekly count by rash onset has come down from its August peak — 228 cases in the week starting August 23, then 164, then 176, and 101 in the week starting September 13. The week starting September 20 shows 40 cases so far, in a count that is still filling in. Underneath that national decline, cases are rising in Pennsylvania, Ohio, and Wisconsin, according to the Johns Hopkins U.S. Measles Tracker that the professional bulletin IZ Express uses for its own state-by-state reporting. 2 4

The two counts measure different things. CDC's national page lists one death for 2026, marked as subject to change, and states that the agency is working with the Council of State and Territorial Epidemiologists on a standard case definition so jurisdictions classify measles deaths the same way. Pennsylvania did not wait for that definition. Its health department published its own — a measles-associated death is one that occurs within 30 days of symptom onset in a person with clinical evidence of measles infection and a positive laboratory test, and that is not due to an unrelated cause — and has confirmed four deaths under it. 2 5

The state reported two of those deaths on August 25, calling them Pennsylvania's first measles-associated deaths in 35 years. The two were unvaccinated infants in Lancaster County. It confirmed two more on September 15: an unvaccinated 40-year-old woman in Jefferson County and an unvaccinated 18-year-old in Mifflin County, who died of acute disseminated encephalomyelitis, a rare inflammation of the brain that measles can trigger. All four occurred within 30 days of symptom onset, and each was investigated with the local coroner's office before being announced. 3 4

The state's response is measurable. Pennsylvania health care providers administered more than 46,000 MMR doses in August 2026, against roughly 25,000 in a typical month, an increase of 84%. State health centers have given nearly 4,400 doses at 140 pop-up vaccination clinics since the outbreak began in late April, and more than 6,800 doses across the state this year. 3

The population-level picture is unchanged. Two doses of MMR are 97% effective at preventing measles, one dose is 93%, and kindergarten MMR coverage stood at 92.4% for the 2025–26 school year, below the 95% level that keeps a community's unvaccinated members protected. 2

What this season's shot can do, and the number still missing

CDC has yet to publish a vaccine effectiveness estimate for the 2026–27 season. Its vaccination-trends page, reported September 25, carries 2025–26 data through May 23 and states that weekly updates for that season ended May 29. The agency's effectiveness index lists seasons only through 2025–26, both marked preliminary. 6 7 A season's first estimate follows its cases, and the past two seasons' first numbers arrived in February and March.

Last season's figures remain the working expectation. In CDC's largest network, which covers outpatient and emergency-department visits, vaccination lowered the odds of testing positive for flu by 36%, with a confidence interval of 33% to 39%. For children 6 months through 17 years, estimates were 38% and 41%. For adults 65 and older, the estimate was 30%. Hospital-based estimates were close to those: 31% across all ages. 8

A study published September 26 in Clinical Infectious Diseases measures the other half of what a flu shot does. Researchers enrolled adults hospitalized with acute respiratory illness at 26 U.S. medical centers between October 1, 2024, and April 30, 2025 — a severe season — and compared the vaccination odds of patients who tested positive for influenza with those who did not. Vaccination reduced the odds of being hospitalized with influenza by 40% (32% to 47%), and the effect held across age groups and virus types. It also reduced the risk of the worst in-hospital outcomes: ICU admission by 58% (47% to 67%), invasive organ support by 58% (44% to 69%), and death by 52% (18% to 71%). 9

Those two studies answer different questions. The 36% figure describes how often a vaccinated person avoids flu infection altogether. The 40% to 58% figures describe what happens when someone is vaccinated and gets sick enough to be hospitalized anyway. Both are reasons the shot is worth an appointment in September rather than a debate in November.

The pipeline, the guidance, and one study about the vaccine itself

Moderna's mFLUSIVA remains where it was on August 5: approved for adults 50 and older, with the 65-and-older indication granted under accelerated approval based on immune responses, and expected to be available during the 2026–27 respiratory season. The company's announcement still offers no local stocking, price, or coverage information. 10 Pfizer published no respiratory-vaccine release this week; the newest entry in its newsroom remains the August 27 approval of the XFG-adapted COMIRNATY formula. 11

The new detail this week came from professional guidance rather than a company. Immunize.org's September 23 bulletin (IZ Express issue 1894) reports that its 2026–27 influenza resources now incorporate the mRNA flu vaccine in both the adult and pediatric standing orders — the documents that let a clinic or pharmacy vaccinate without an individual prescription — and in the screening checklists. One of those resources carries a caution worth knowing: the mRNA influenza vaccine is not to be used during pregnancy because it has not yet been studied in pregnant people. The same bulletin reports that the RSV standing orders were refreshed for 2026–27 against the September 2 guidance from the American Academy of Pediatrics, the American College of Obstetricians and Gynecologists, and the American Academy of Family Physicians. 4

The routine immunization schedule held steady this week. CDC's schedule pages still carry the July 2, 2025 addendum, and the agency's interim clinical considerations for this season state plainly that the recommendations from the July 2025 immunization schedule remain in effect for 2026–27. 12 13 The FDA's vaccine advisory committee meets October 1 to select strains for the 2027 Southern Hemisphere season, a decision that leaves this season's U.S. formula untouched. 14

The immunology journals the channel follows published this week into cancer, allergy, malaria, and basic immune regulation: Immunity carried a structural study identifying antibody targets on the malaria parasite (September 24) and two papers on allergic immune memory (September 22 and 23); Nature Immunology published work on regulatory T cell stability (September 21) and on how metastatic tumor cells release antigens (September 22); Cell's recent output runs to cancer biology, neuroscience, and bacterial cell biology. 15 16 The clinically relevant study of the week therefore came from Vaccine, and it concerns the measles vaccine itself.

Researchers linked England's hospital records to MMR vaccination records for children born between 2000 and 2019, looking for idiopathic thrombocytopenic purpura — a rare condition in which the immune system destroys platelets. After the first MMR dose, the relative incidence of ITP in the following six weeks was 2.38, an attributable risk of about one case per 42,900 first doses. There was no increased risk after the second dose (relative incidence 0.96). Among the 336 children who developed ITP after their first dose and went on to receive a second, the second dose carried no increased risk either, which is why the authors conclude those children can safely complete the series. 17

Set against a national measles count of 3,659 cases and 327 hospitalizations, one extra ITP case per 43,000 first doses is a small number on a large scale. It also describes a condition that is usually treatable, and it identifies the children for whom the second dose is safe. The practical question for a family is which risk is larger: about one extra, usually treatable, case of ITP per 43,000 first doses, or measles in a year that has hospitalized 327 people.

What to do this week

Book flu shots for everyone 6 months and older. September and October suit most people, with vaccination ideally finished by the end of October; protection takes about two weeks to develop. 18
Start a first-time flu shot for a young child now. Children 6 months through 8 years who need two doses should receive the first as soon as vaccine is available, because the second comes at least four weeks later. 18
Ask for a preferred formulation if someone in the house is 65 or older. Fluzone High-Dose, Flublok Recombinant, and Fluad Adjuvanted are the three CDC recommends preferentially for this age group; if none is in stock, any age-appropriate flu vaccine works. 18
Find the MMR records for school-age children. Two documented doses need no further action. A single dose on record, or no record, is the gap to close with a pediatrician, a state immunization registry, or a county health department. 2
Complete MMR at least two weeks before an international trip. The measles vaccine needs that long to work, and travel is how the virus keeps re-entering the country. 5

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.