While doctors’ offices are starting to get shipments of this year’s influenza vaccine, health officials say residents should wait until mid-September to mid-October to get the shot.
According to Jack Sullivan, an epidemiologist with the Valley Health Regional Collaborative, the flu vaccine is effective and offers protection for about six months, meaning if you get the shot in August or early September, you will not be protected all the way until the tail end of flu season. Sullivan said people who get the flu vaccine in mid-September to mid-October are generally protected through March.
“Unlike COVID, which is pretty much year-round, the flu has a really defined season from October to March,” Sullivan said. “It’s extended to the spring a little longer than it used to because people are getting their vaccines in August, earlier than they should.”
The flu is a respiratory disease caused by the influenza virus, which can cause fever, cough, sore throat, aches, chills, runny nose and fatigue. The virus can be spread from person to person through mucus and saliva, and can survive briefly on surfaces such as tabletops, doorknobs, toys and phones. Symptoms typically appear between one and four days after contracting the virus and typically last between five and seven days.
Sullivan explained that when doctors’ offices receive their annual supply of the vaccine, they often send messages to patients encouraging them to schedule their flu shots, and that many see these messages and get their vaccine immediately.
According to Massachusetts Department of Public Health data from last flu season, flu activity in western Massachusetts was minimal until December 2025, then began to rise to the high and very high categories in December and January before slowing to moderate in February. Cases picked up again in March, and the activity level was classified as moderate and then high throughout March and early April for the rest of the reporting season.
Sullivan said getting the shot too early could result in being unprotected at the end of the season, but getting it too late could result in people being unprotected at the beginning of the season. It takes two weeks for the vaccine to reach full protection, he said, and flu season begins in October, with cases really starting to spike in November. The vaccine loses effectiveness by approximately 6% to 10% per month.
“The prime time to get it is mid-September to mid-October,” he reiterated.
The last flu season (fall 2025 through spring 2026) resulted in 322 deaths across Massachusetts, including nine pediatric deaths. The year before, the Department of Public Health reported 470 deaths, including 10 involving children.
According to data from the Valley Health Regional Collaborative, which serves Greenfield, Montague, Deerfield, Shutesbury, Sunderland and Leverett, there were 373 cases reported in the six communities last year. The season peaked in December with 125 cases.
Greenfield had the highest case count among the six municipalities, with 181 cases, followed by Montague, with 69 cases.
“You can’t really tell what kind of season we’re gonna have,” Sullivan said. “The past two years we’ve had two of the highest numbers of cases we’ve had in decades. … Those two years combined were the harshest that we’ve seen in decades.”
Sullivan noted a new variant emerged last December, which the vaccine was not effective against, contributing to the high level of flu deaths.
This year’s flu vaccine is trivalent, Sullivan said, meaning it’s formulated to be effective against three different flu variants.
For the 2026-2027 flu season, the U.S. Food and Drug Administration’s Vaccines and Related Biological Products Advisory Committee recommended that this year’s flu vaccine tackle two “A” variants and a “B” variant.
Sullivan added that for the first time, the FDA approved a new mRNA-based flu vaccine, mFLUSIVA, produced by Moderna. It’s currently approved for use in adults ages 50 and up.
A study published in May in The New England Journal of Medicine found that the mRNA-based vaccine was up to 27% more effective in preventing flu than other available flu shots.
In a statement, Stéphane Bancel, CEO of Moderna, said the vaccine will help keep senior citizens — who are at the highest risk of complications, including death, associated with the flu — safe.
“The FDA approval of mFLUSIVA, our fourth approved product in the United States and the first mRNA-based flu vaccine, demonstrates the continued strength and versatility of our mRNA platform,” Bancel said. “Flu remains a significant public health challenge, and mFLUSIVA provides an important new option for America’s seniors. This approval also reflects the ongoing potential of our mRNA platform to help address important public health challenges through continued scientific innovation. We are grateful to the clinical trial participants, investigators, regulators and Moderna teams whose contributions made this milestone possible.”
Compared to traditional vaccines, which inject inactivated, attenuated or only parts of a virus into the body to train the immune system, mRNA vaccines do not carry any viral components. According to the National Institutes of Health, mRNA, or messenger ribonucleic acid, can carry instructions for building proteins that can then fight the virus. The vaccine trains the body to recognize and fight viruses without ever exposing the body to the virus itself.
The state Department of Public Health recommends that all people 6 months old and older get vaccinated for the flu, with no preference for type of vaccine. For the 2025-2026 season, the department recommended those over the age of 65 get either the Fluzone High-Dose trivalent vaccine, Flublok trivalent recombinant flu vaccine or Fluad trivalent adjuvanted flu vaccine; however, the state has not yet issued recommendations for the upcoming 2026-2027 flu season.
