Americans are being urged to schedule their annual flu shot for October, according to the Centers for Disease Control and Prevention (CDC), after last year's respiratory season brought a severe surge driven by a highly mutated strain known as the 'super flu.'
The 2025-2026 season saw at least 32 million flu cases in the United States, the CDC reported, along with about 390,000 hospitalizations and 24,000 deaths. The surge was driven by subclade K, a highly mutated variant of the Influenza A (H3N2) virus that caused a rapid and severe spike in cases nationwide.
Influenza, commonly known as the flu, is one of the most common and highly contagious respiratory infections, impacting around eight percent of the US population each year. It can cause body aches, headaches, fever and a cough, and can lead to more serious complications including pneumonia and influenza-associated encephalopathy (IAE), a severe brain dysfunction condition.
When to get the shot
Flu season normally starts in October, with infection rates peaking between December and February before dwindling by springtime, per the CDC. As of September 5, the US was experiencing a minimal activity level for flu cases.
The flu shot provides protection for about six to eight months, so experts say timing matters. Getting vaccinated too early could mean the protection wears off before flu season actually ends.
While pharmacies begin stocking the vaccine in August and promoting it in September, doctors agree these months are still too early for most people to get the shot.
October is considered the ideal month to get vaccinated, with the CDC recommending vaccination by Halloween for the upcoming 2026-2027 respiratory season.
"October is when I recommend getting the vaccine as there is more actual influenza activity then - there is very little now," infectious disease expert Dr Amesh Adalja told Prevention.com. "The vaccine will last further into the season if administered in October," he added.
Exceptions to the rule
One exception for an early flu shot is children under eight years old who have never received one, as they need two doses spaced apart to build immunity.
People at high risk of flu complications, such as those with asthma, may also want to consider getting vaccinated earlier than October.
Understanding flu strains
There are three different flu virus strains that cause illness: influenza types A, B and C. Influenza type A can infect both people and animals, while type B is usually found only in humans and is generally associated with less severe infections. Type C occurs much less frequently than A and B and causes only minor illness in humans.
The seasonal flu shot, which is updated every year as the virus mutates, protects against influenza types A and B, as these are the most common and severe strains.
Symptoms and how well the vaccine works
Symptoms of the flu include fever, cough, sore throat, stuffy nose, headaches and fatigue. While most people recover within a week, some may develop complications such as pneumonia, which can be life-threatening and require medical treatment.
The flu shot is one of the most effective preventative measures against infection, reducing the risk of doctor visits by 34 percent and the risk of hospitalization by 30 percent, according to the CDC. However, it can take up to two weeks for the body to develop antibodies after vaccination, so doctors recommend getting the shot a few weeks before an event or gathering where large numbers of people will be indoors.
Who is most at risk
Anyone can catch the flu, but those most susceptible include people 65 years and older, those with chronic medical conditions, pregnant women, and children under five.
Last year's dominant strain, dubbed the 'super flu,' was brand new to people's immune systems, making them highly vulnerable and at increased risk of severe, hospitalizing illness. While symptoms were the same as other flu strains, experts warned the variant was causing more severe illness, especially in children, with signs including week-long fevers and a cough that led to trouble breathing. Super flu's symptoms appeared similar to previous influenza A strains, though doctors noted they could be more severe.
Prevention and treatment
Health officials recommend regular handwashing and avoiding contact with people who have flu-like symptoms to reduce the risk of infection.
Treatment includes rest, staying hydrated, taking over-the-counter medication such as Mucinex, or, in severe cases, prescription antivirals such as Tamiflu.
