Are Flu Shot Side Effects Worse This Year?

An illustration of people who got shots with sore arms on a pale yellow background.


Key Takeaways

  • There is no evidence that this year’s influenza vaccine is causing more or worse side effects than shots from previous years.
  • Last year, the United States had a relatively mild flu season, thanks in part to the pandemic precautions put in place against COVID-19.
  • Experts are concerned that with mask mandates and social distancing rules starting to lift, the flu season in the U.S. might be worse this year, making it all the more important that people get a flu shot.

With the possibility of both a stronger flu season and another wave of COVID-19 cases during the winter months in the United States, getting both a COVID vaccine and an influenza vaccine is important.

However, some people who have gotten a flu shot this year have said that they have felt stronger side effects from the influenza vaccine this year compared to past years.

Since the perception of more or harder-hitting flu vaccine side effects is only anecdotal and not backed by evidence, Verywell asked experts to weigh in on the reports.

Flu Shot Side Effects—Worse This Year?

Jennifer Kaufman, MD, a pediatrician at Stanford Children’s Health, told Verywell that so far this year, they "have not heard complaints that the flu vaccine is causing more side effects than in past years."

In the U.S., flu season typically starts in October and peaks in February.

Kaufman has been getting the "usual reports of mild fever and some body aches for one to two days after the flu vaccine" but points out that this does not happen to everyone. "We cannot really predict who will and won’t develop these side effects,” she said.

Which Vaccine Is Available This Year?

During its annual Vaccines and Related Biological Products Advisory Committee (VRBPAC) meeting in March, the U.S. Food and Drug Administration (FDA) recommended a quadrivalent vaccine for the 2021-2022 flu season, which protects against four different influenza strains—two influenza A and two influenza B.

Jennifer Kaufman, MD

Actually having the flu is, in fact, much worse than the side effects of the vaccine and typically lasts much longer.

— Jennifer Kaufman, MD

A trivalent version of the vaccine—which contained three influenza strains instead of four—has been authorized in previous years, but Kaufman said that the quadrivalent vaccine “does not produce more side-effects,” than the trivalent version and more importantly, “it does offer better protection.”

Another misconception about flu vaccines is that they actually give you the flu, which is false.

“It has been very common in the past (before COVID) for people to mistake the side effects of the flu shot with actually having the flu,” Kaufman said. “Actually having the flu is, in fact, much worse than the side effects of the vaccine and typically lasts much longer.”

Flu Shot vs. COVID Vaccines

Since the COVID-19 vaccines started rolling out in December 2020, over 67% of the U.S. population have received at least one dose. Some people reported side effects of the COVID shot that kept them home in bed for a day or two.

While the COVID vaccine does not protect against the flu (nor does the flu shot protect against COVID) the side effects of the vaccines are similar. A sore arm where the shot was given, fatigue, fever, and body aches, can happen with either vaccine.

It's also completely safe to get both shots at the same time. The Centers for Disease Control and Prevention (CDC) has given the green light for people to get both a COVID-19 vaccine and the flu shot, along with other vaccines that they might be due for, at the same visit.

According to the CDC, the immune response that is triggered after you get a vaccine is usually the same whether you get one shot at a time or multiple shots at once.

Are We In For a Worse Flu Season?

Lockdowns and masking mandates seemed to help keep the flu at bay last year, with only 0.2% of collected specimens testing positive for influenza compared to an average of 30.3% specimens testing positive during the previous three flu seasons.

Jennifer Kaufman, MD

Experts are very concerned that the flu season will be worse this year.

— Jennifer Kaufman, MD

However, since many states have reduced or eliminated pandemic precautions, the U.S might see an influx of flu cases this year combined with a wave of COVID-19 cases—what some are calling a “twindemic.” 

“Experts are very concerned that the flu season will be worse this year,” Kaufman said. “No one really knows if there will be increased complications for patients who develop influenza and COVID at the same time. This emphasizes the importance of getting vaccinated for both COVID-19 and influenza.”

While wearing a face mask has proven very helpful in stopping both the spread of the flu and COVID, getting vaccinated is the best way to protect yourself.

Protecting the Most Vulnerable

Some kids can now get vaccinated against COVID, but parents and caregivers should not forget to get them a flu shot, too. While the COVID vaccine is currently only for kids ages 5 to 11, babies as young as six months old can get a flu shot.

During the 2020 lockdown, infants and young children were shielded from the flu virus, which may make them more vulnerable during this year’s flu season because they were not exposed to the virus as they typically would be.

Kaufman says that children under the age of 1 or 2 years are generally more at risk for serious complications if they get the flu, but this year might be even tougher on them.

“The number (of vulnerable children) is even larger this year because it will include last year’s babies as well as this year’s babies,” Kaufman said. “We are already seeing this with other viruses that are circulating earlier in the year than they normally do because there are more people around who are susceptible.”

What This Means for You

There is no evidence that this year's flu shot is causing more side effects than in previous years. However, because the flu season is likely to be worse this year and may overlap with a winter spike in COVID-19 cases, it is extremely important to get vaccinated for both COVID and the flu this fall.

6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Centers for Disease Control and Prevention. Flu season.

  2. U.S. Food and Drug Administration. Influenza vaccine for the 2021-2022 season.

  3. Centers for Disease Control and Prevention. Frequently asked questions about COVID-19 vaccination.

  4. Centers for Disease Control and Prevention. Flu season summary.

  5. Hackensack Meridian Health. Should I wear a mask during flu season?

  6. Centers for Disease Control and Prevention. Flu & Young Children.

By Amy Isler, RN, MSN, CSN
Amy Isler, RN, MSN, CSN, is a registered nurse with over six years of patient experience. She is a credentialed school nurse in California.