For the last two years, the flu has been essentially MIA, with cases plummeting alongside the social distancing, mask-wearing, and other steps people have had to take to slow the spread of COVID.
But this year the influenza virus, as rusty and dusty as it may be, seems likely to come roaring back — and that means it's more important than ever to get your flu shot, experts say.
Typically characterized by fever, muscle aches, headaches, and fatigue, the flu can become serious or life-threatening, especially for babies and immunocompromised, pregnant, and older people. It can cause complications like pneumonia and inflammation of the heart, brain, or muscle tissues. The virus can also aggravate chronic medical conditions like asthma and heart disease.
About 20,000 to 40,000 people can die of influenza each flu season, which generally starts in October and may stretch into May. (The peak months are generally December to February.) The 2017-2018 season was particularly bad, with 52,000 deaths.
However, that number dropped to an estimated 5,000 to 14,000 deaths in 2021-2022, which was lower than any of the 10 flu seasons before the pandemic. The year before that, influenza activity was so low that the CDC couldn’t even generate burden estimates, which it does every year.
With cases expected to rise this season, a flu shot can help keep the risks at bay. There are at least two main reasons why you should get one every year: your immunity from vaccination and infection decreases over time, and flu viruses change constantly, meaning any protection you’ve acquired from previous seasons could mean zip this year.
Another reason why it may be extra important to get a flu shot this year is that your protection against the virus may be, relatively speaking, not the greatest following two years of little to no exposure.
“In other words, vaccination makes more people resistant to infection the following year because they have that vaccine-induced immunity that was then possibly boosted by an infection,” said Johns Hopkins virologist Andrew Pekosz. “But without [getting infected] for several years, we do run the risk of having even more people be susceptible to flu than we normally would, and that is another reason why we would be concerned about a large flu season if flu does come back.”
Here’s everything to know about flu shots this influenza season.
Why you should get a flu shot this year
The US looks to the Southern Hemisphere’s flu season, which occurs earlier than in the North, to get a glimpse of how the virus might behave. Unfortunately, Australia’s bout with influenza this year was particularly “concerning,” Pekosz said.
Not only did the country have a high number of cases, but it also experienced them earlier on than usual.
“Those two things are concerning for us as we now think about how to prepare for a potential flu season along with perhaps some COVID increases,” Pekosz told BuzzFeed News, “especially since we're all back to working inside, schools are full time, and we're not doing a lot of our public health interventions anymore.”
And based on Australia’s data so far, children in the US may be more likely to be affected by the flu this season, Pekosz said: “Those are people that haven't had as much exposure to flu, haven't seen a lot of flu seasons, and perhaps were even more susceptible than older parts of the population.”
COVID preventive measures like masking are also down significantly compared with the last two years.
Vaccination usually offers protection for the duration of the flu season. You can still get sick, but a flu shot should reduce the chances you’ll need emergency medical help. A 2021 study found that adults who received a flu shot had a 26% and 31% lower risk of being admitted to the ICU and dying from the flu, respectively, compared with unvaccinated adults.
Flu vaccines protect against four flu viruses that may circulate in a given season. So if the vaccine fails to properly protect you from one of them, it may still protect you against the others.
However, like the COVID vaccines, that protection can wane over time. A CDC analysis of flu vaccine effectiveness from 2011 to 2015 found that protection dropped by about 6-11% per month, depending on the virus strain involved, and remained intact for about five to six months after vaccination. Generally, vaccine effectiveness decreases a tad faster for people ages 65 and older.
What to know about this year’s flu shot
First and foremost, everyone ages 6 months and older should get a flu shot, health officials say, with some specific recommendations or exceptions based on age, health status, and history of allergies.
And yes, you can get any one of your COVID vaccines and/or boosters at the same time as your flu shot. Most health experts, including Pekosz, recommend it, mostly because of its convenience. (Just don’t get your shot if you still have COVID; wait until you’ve recovered so you don’t infect anyone in the process.)
The best time to get your flu shot is in October, but if you miss that window, you should still get it at your earliest convenience. It’s better late than never because flu seasons are becoming more unpredictable and generally shifting to occur later in the year, the CDC says, with some seasons peaking as late as March.
And similar to COVID vaccination, you should still get a flu shot even if you’ve already contracted influenza because the vaccine may protect you against other circulating flu viruses.
This year, the CDC recommends people ages 65 and older receive a higher dose or flu vaccine with an adjuvant (an extra ingredient that improves immune response): Fluzone, Flublok, or Fluad — all of which may cause more temporary side effects such as headaches, fatigue, muscle aches, and pain at the injection site for about one to three days. The new recommendation is based on evidence that shows these shots are more effective in older adults than the standard ones, which are still recommended for all other age groups.
The guidance is particularly important because people 65 years and older are more likely to experience severe outcomes from the flu. The CDC says that about 70-85% of flu-related deaths and 50-70% of hospitalizations have occurred in this age group.
Other people at risk for a severe flu infection are those with chronic medical conditions such as heart disease, diabetes, or asthma, those who are pregnant, and children under five years old, especially those under two.
The good news so far is that this year’s flu shot appears to match the viruses that are currently circulating, Pekosz said, but given the lack of flu cases in recent seasons, “we are really worried that we haven't been picking up enough strains to really get a good sense of how the virus has been doing during the pandemic.”
It typically takes about nine months between when scientists decide which viruses they want the next year’s flu vaccine to target and when it’s time to vaccinate people, Pekosz said, which means they are making decisions before the current flu season is even over. “That’s not an ideal place to be,” he added, especially because the circulating flu viruses can still mutate toward the end of the season.
The delay ultimately comes down to how the flu vaccine is made, which is a much longer process than that of the COVID vaccines. Both Moderna and Pfizer, the companies behind the coronavirus shots, are conducting clinical trials for their own influenza vaccines — a development that would be a “real game changer,” according to Pekosz, because “we could wait until the end of the flu season to make the decision about the right virus strains and be better prepared for the following flu season.”
In the meantime, it will certainly help to wear a face mask when in crowded indoor areas and to stay home when sick. And remember: There are four different and effective antiviral medications that can help you feel better and prevent serious illness; they work best if taken within 48 hours after your symptoms begin, the CDC says.
“The more you can do to help protect you from severe disease, the better,” Pekosz said.