With flu season in full swing, sore upper arms abound.

So when we asked readers which of your flu questions we should look into, it’s no wonder this one got the most votes: “Why does the flu shot hurt so much? I get the shot every year, and my arm is always sore for a few days after.”

The answer is pretty simple. And given that it’s November, we’ll answer in holiday terms:

Think of your arm as a Butterball turkey, pumped full of liquid to plump the bird up. Flu shots work the same way, delivering “a great big wad of fluid” from a syringe into your muscle, said Dr. John Dunn, medical director for preventative care at Kaiser Permanente Washington. That makes your muscle sore.

The flu shot may seem like it hurts more than other shots do, but it’s all a matter of perspective, Dunn said. Most people get the flu shot regularly, whereas most other vaccines are administered during childhood, Dunn said.

“The reason it strikes you is that you don’t get shots anymore,” he said.

The flu has had time to circulate, with kids being back in school for a couple of months. While it has been mild so far this year, the number of people falling ill is increasing, according to the Centers for Disease Control and Prevention (CDC).


Washington’s flu season mirrors what is happening nationally. One adult has died from the virus this season, the state’s tracking data shows.

The state Department of Health (DOH) tracks the flu season from the fall of one year through the fall of the following year. For the season spanning Sept. 30, 2018, to Sept. 28, 2019, there were 245 confirmed deaths from influenza. King County residents accounted for 54 of those deaths, Piece County 42, Snohomish County 26, and 11 in Kitsap County. During the 2017-18 season, 296 people died, which was the most this decade. The season with the fewest flu deaths in the past 10 years came in 2011-12, when 20 people died.

Everyone older than 6 months should get vaccinated against the flu every year, the CDC advises, even during a mild flu season like we are experiencing.

“Everybody reacts a little bit differently” to getting the shot, Dunn said. If your arm gets uncomfortable, “The key thing for people to do is to keep using your arm and moving it around.”