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It's flu season and flu shot time. Why you shouldn't wait to get the vaccine this year

Don't put off getting the flu vaccine in 2021. Here's why.

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It's flu season. And flu shot season.

Sarah Tew/CNET
For the most up-to-date news and information about the coronavirus pandemic, visit the WHO and CDC websites.

Flu season is here again, and those virus infections will overlap with the ongoing COVID-19 pandemic, creating the possibility of a "twindemic" of two distinct, dangerous illnesses that cause (among other things) respiratory distress, hospitalizations and death for millions of people. Nationwide lockdowns that kept people distanced, mixed with the annual flu shot, largely helped dodge the double blast of infections last year. But this year, things are different. Many other viruses, like RSV and rhinovirus, are coming back. And the flu likely will follow suit. 

While the US saw a steep rise in coronavirus infections in the winter, the spread of influenza was uncommonly light. However, this year could return to the typical pattern, in which millions of people in the US catch the influenza virus, according to the Centers for Disease Control and Prevention, and tens of thousands die from flu-related causes. With COVID-19 vaccines and booster shots now authorized -- even mix-and-match shots -- intermingling is expected. (And COVID-19 antiviral drugs are on the way.) And with that, a possible increase in the flu, alongside new waves of delta variant COVID infections at a time when peoples' stance on masking and social distancing have become political issues, not just public health concerns.

We talked with three flu-vaccine experts about what to expect this flu season -- read on for their practical guidance and concerns. For more on the flu, here's where you can get your shot in 2021, which flu-shot side effects you may experience and why epidemiologists suggest taking both a COVID-19 vaccine and flu shot.

Get your flu shot. Now

In the US -- and the rest of the northern hemisphere -- flu season usually runs October to May, according to the experts we spoke to. But the flu virus is less concerned with the seasons and more interested in spreading. So the timing this year could be less predictable, experts warn, with last year's light flu season and our own changing behaviors around the pandemic. 

But you don't want to try to time your flu shot for when the flu will hit. To be ready, experts recommend you get your flu vaccine now.

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"We have a normal time when we expect the flu," Peter Chin-Hong, a medical doctor and professor in the Health Division of Infectious Diseases at the University of California, San Francisco, told CNET. "But this year, it could be atypical or drag on longer, so that's what people need to be prepared for."

A similar shift in the timing of a seasonal virus infection happened this summer when the US and Japan saw a spike in respiratory syncytial virus, or RSV, infections in school children, Chin-Hong said. That's because students were not exposed to the virus the winter before -- when RSV infections normally occur -- and so didn't have immunity built up, which allowed the virus to spread in the summer instead.

What to know about the flu vaccine's effectiveness this year

Vaccine-makers monitor which flu strains are currently circulating and forecast which are mostly likely to become the dominant strains during the upcoming flu season. These drug manufacturers then produce a flu vaccine -- your flu shot -- using three and sometimes four of the most likely flu strains. 

The effectiveness of the vaccine at preventing infection varies year to year, ranging from 19% efficacy in the 2014-2015 season to 60% in 2010-2011. Last year, the flu shot was 39% effective in preventing infection. 

And last flu season, about half of US adults and children got a flu shot, according to the CDC. Combine that with the steps the US took to check the spread of COVID-19, and you get a number of reported flu cases in the US that seems like a typo, it is so unbelievably low: 2,038 flu cases reported during the 2020-2021 flu season vs. 38 million cases reported in the 2019-2020 season.

This year, because of last year's light flu season, the vaccine-makers had less to go on to make their predictions and created a vaccine containing four likely flu strains -- called a quadrivalent flu vaccine -- to increase the chances of covering the dominant strain this year. 

"There was enough data to make a good educated guess," said L.J. Tan, chief strategy officer for the Immunization Action Coalition, a nonprofit organization that works to increase vaccination rates. "Right now we are confident we got it right."

As with the COVID-19 vaccines, the flu shot is not 100% effective in guarding against infection. But like the coronavirus shots, the flu vaccine can blunt the severity of the virus if you do catch it. The CDC said getting vaccinated for flu can reduce the risk of having to go to the doctor 40 to 60%

And don't worry about more serious side effects with a four-part flu vaccine: Whether the vaccine is made using three components or four, the side effects should be the same, Chin-Hong, the UCSF doctor, said.

Expect to book an appointment to get your flu shot

If you're used to walking up to your local pharmacy, hospital or clinic to get a flu shot whenever it's most convenient to you, you may find this year that you have to schedule an appointment instead. 

Signs in a local pharmacy instruct customers to make an appointment for both flu and COVID shots, and Walgreens' chief medical officer, Kevin Ban, recommends scheduling COVID-19 and flu vaccinations online. 

"We are doing as much as possible to make it easy for people to schedule their appointments and get seamlessly vaccinated," Ban said, adding that you can also call Walgreens' toll-free number to make an appointment.

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Now's the time to get ready for flu season.

Sarah Tew/CNET

It's safe to get your COVID and flu shots simultaneously

The COVID pandemic continues to cause infection, hospitalization and death, with hospitals in the hardest-hit areas once again at the limit of their ability to treat patients. But the flu shot should be as easy to get as the COVID-19 vaccination.

In fact, the CDC has said it's safe to get a flu shot and COVID vaccination in the same sitting. (Vaccine-maker Moderna said it's working on a combination COVID-19/flu vaccine, but that combo won't be available this year.)

For more on vaccines this fall, here's what we know about the Pfizer COVID-19 booster, the Moderna vaccine booster and the Johnson & Johnson booster. And here is the latest on Pfizer's antiviral pill.

The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.