How Effective is the Flu Shot This Year? Get the Facts

Discover how effective this year's flu vaccine is at preventing influenza strains and reducing illness severity. Learn about flu shot effectiveness from trusted sources.

A new study in The Journal of Infectious Diseases shows that flu shots really work. They cut the chance of going to the ER for flu by almost half. And, they lower the risk of needing hospital care by over a third for adults in the U.S. last flu season.1

The flu hit hard and early in the 2022-2023 season, with lots of people needing hospital care. This year, other viruses spread with the flu too. The study proved the flu shot lowered the risk of serious flu cases that needed ER or hospital visits by significant amounts. The benefit varied by age and where people got care. Older adults saw a 41% drop in hospital visits thanks to the vaccine.1

The study got its info from the VISION Vaccine Effectiveness Network. This group brings together the CDC, Westat, and many healthcare groups to check how well vaccines work in the real world.

Key Takeaways

  • Flu vaccination reduced the risk of flu-related emergency department and urgent care visits by almost half and hospitalizations by more than a third among U.S. adults during the 2022-2023 season.
  • Flu vaccination was particularly effective for older adults, with a 41% reduced risk of hospitalization.
  • The 2022-2023 flu season saw unusually early and intense flu activity, with high hospitalization rates and co-circulation of other respiratory viruses.
  • Flu vaccine effectiveness can vary by age group and care setting, highlighting the importance of annual vaccination.
  • The VISION Vaccine Effectiveness (VE) Network, a collaboration between the CDC, Westat, and healthcare organizations, provided the data for this study.

Understanding Flu Shot Effectiveness

Experts look at how well the flu vaccine protects us by comparing who gets the flu when they’ve had the shot and when they haven’t.2 Their findings show the shot lowers the chance of getting sick by 40% to 60% in most people during good match years.2 Still, this number can change due to many reasons.

Measuring Vaccine Efficacy

The power of the flu shot changes based on a few things. These include if the vaccine matches the viruses going around, how our bodies react to it, and how bad the flu season is.2 Teams like the CDC’s Influenza Vaccine Effectiveness Networks work to figure out the shot’s actual impact in different scenarios.2 Their work helps us understand how useful the flu shot really is.

Factors Influencing Effectiveness

Vaccines do a better job against certain flu strains than others.21 It’s also clear that the shot doesn’t work as well on viruses that are very different than what’s in the vaccine, especially as people get older.2 Knowing this can guide us in picking the best ways to prevent flu.

Flu Shot Effectiveness in 2022-2023 Season

The CDC says the 2022-2023 flu vaccines lowered the risk of influenza A hospital stays by 35%. They were also 44% effective in cutting down visits to the ER and urgent care.3 How well they worked depended on age. Those 65 and over were 41% less likely to be hospitalized. But for adults, 18-64 years old, the drop was only 23%.3 Yet, they did help keep high-risk groups safer. This includes older folks and those with health issues.3

Reduced Risk of Hospitalizations

Vaccines made a big difference in the U.S. They slashed the need for ER and urgent care visits by about half. They also cut hospitalizations by more than a third.3 Even kids and teens benefited. Almost one-third of their flu-related hospital stays were kept at bay.3

Varying Effectiveness by Age Group

Age played a big part in how well the flu shot worked. Children from 6 months to 4 years old saw visits to the ER and urgent care fall by 53%. Hospital stays dropped by 56%.3 Kids aged 5 to 17 had a 38% lower ER and urgent care visit risk. Their hospitalizations were down by 46%.3 Adults under 65 got a standard shot. Those 65 and up got a different kind that works better.3

Flu Shot Effectiveness in 2023-2024 Season

The CDC estimates that flu vaccines for 2023-2024 are 41% to 44% effective in adults, reducing flu-related hospitalizations. For kids, the effectiveness ranges from 52% to 61%.4 This shows that the flu shot is doing well this season, like in the past. It targets the main strains, both type A and B.5

In the U.S., the flu shot worked best for kids in the 2023-24 season, with effectiveness ranging from 46% to 89%. This depended on the type of flu and where the kids lived.5 How many kids got vaccinated varied, from 8% to 31%.5 Against Influenza B, some places saw up to 89% protection.5 But, protection against Influenza A was a bit lower, from 40% to 61%.5 The NVSN network noted that the flu shot worked less well for outpatient versus inpatient visits.5

For the 2023-2024 season, the U.S. should get between 156.2 million to 170 million flu vaccine doses.6 Most of these vaccines will not have thimerosal or have it in a reduced amount (91%).6 Also, about 21% of them will be egg-free.6 They will all be quadrivalent, offering protection against four flu virus types.6

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flu shot effectiveness

Flu Vaccine Strain Coverage

Each year, experts update flu vaccines to fight the most common flu strains.2 For 2023-2024, the vaccines will handle H1N1, H3N2 of influenza A, plus Victoria and Yamagata types of influenza B.2

Influenza A Subtypes

Flu A viruses like H1N1 and H3N2 usually hit hard, leading to more severe sickness.2 This season’s shots aim to guard against these tough A types.2

Influenza B Subtypes

This year, the flu vaccines also cover B viruses, including Victoria and Yamagata types.2 But, the Yamagata B type has been taken out due to not showing up during the pandemic.2

The goal is to protect against the flu strains most likely to spread.2 This tailored effort boosts flu shot effectiveness and prepares us for the flu season.27

Influenza SubtypeVaccine Effectiveness
Influenza A(H1N1)More effectively targeted by current flu vaccines2
Influenza A(H3N2)Less effectively targeted by current flu vaccines2
Influenza B (Victoria)More effectively targeted by current flu vaccines2
Influenza B (Yamagata)Removed from 2023-2024 flu vaccines2

Regular updates to the flu vaccine are made to offer the best protection possible.27 It ensures the shots guard against the flu viruses going around well.27

Flu shot effectiveness

Since the 2003-2004 flu season, the CDC has teamed up with many groups. They include researchers from universities and hospitals.1 Their aim is to find out how well flu vaccines really work. They do this through studies that look at confirmed flu cases.1 Through these efforts, we’ve learned that flu vaccines’ effectiveness usually falls between 40-60%. This is when the virus and the vaccine are closely matched.12

CDC’s Vaccine Effectiveness Networks

The CDC leads networks to watch how good the flu vaccine is in different places and groups.1 These efforts help by studying people who caught the flu (even though they got the flu shot) compared to those who didn’t get vaccinated. This info teaches us a lot about what impacts the flu vaccine’s success.

Historical Flu Vaccine Effectiveness Data

In the past, flu vaccines have been about 40-60% effective when the match is good.1 But, several things can change how well the vaccine works. For example, if the vaccine matches the virus going around, how people’s bodies react to the vaccine, and how serious the flu season is.28

Influenza Virus SubtypeVaccine Effectiveness
Influenza A(H1N1)pdm0956%
Influenza B42%
Influenza A(H3N2)22%

The numbers you see above are from a study that looked at 76 reports. These findings show how the vaccine’s success can change with different kinds of flu viruses in the Northern Hemisphere.2

Importance of Herd Immunity

Herd immunity happens when a big part of a community is immune to a disease. This is great because it protects those who can’t get vaccinated, like babies, seniors, and people with weak immune systems.9 For flu, only about half the people need to be vaccinated to reach this point, which seems quite doable.9 But, to reach this level with a 60% effective vaccine, about 83% of the population must get vaccinated. This is much higher than the current rates in the US, meaning we’re not there yet.9

Protecting High-Risk Groups

Vaccinating a lot of people against the flu helps slow down how fast the virus spreads. This is especially important to protect those at higher risk of getting very sick. These at-risk groups include adults over 65, kids under 2, pregnant women, and those with health problems.10 They’re more likely to face serious health issues if they catch the flu, like pneumonia.10 Getting the flu shot not only helps you but the whole community by lowering the chances of the flu spreading.10

Flu Prevention Measures

The Centers for Disease Control and Prevention (CDC) says getting a flu shot is vital for people ages 6 months and up. It’s the top way to guard against the flu.11 Everyone 6 months and older should get the shot, according to the CDC.11 It takes about two weeks for the vaccine to make you immune.11 The vaccine can decrease your chances of getting the flu by 40% to 60% if it matches the current strains.1 So, getting the vaccine cuts your risk of flu sickness by 40% to 60% during a good match year.1 It also means you’re 40% to 60% less likely to need a doctor during this time.

Importance of Annual Vaccination

Aside from the flu shot, don’t forget about washing your hands often, and covering your mouth when you cough. And if you’re sick, it’s best to stay home.11 New flu vaccines come out each year to combat changing flu types.1 During the 2019-2020 season, flu shots stopped 7 million cases, 3 million doctor visits, and saved many lives.1 They also helped avoid lots of flu-related hospital stays.

Additional Preventive Strategies

Working together on flu prevention, including everyone in a community, can lessen the flu’s impact in general.11 Some people, like those over 65, residents of care facilities, kids, pregnant folks, and those with specific health issues, are at higher risk.1 For older adults, the flu shot is linked to a 40% lower chance of needing hospital care.1 In the 2019-2020 year, it stopped about 100,000 hospitalizations.

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Potential Side Effects

Flu vaccines are safe for most people. You might have a bit of soreness, redness, or swelling where you got the shot. You could also feel a little tired, have a mild fever, or sore muscles. These go away after a few days.12

Feeling sick from a flu shot is not common. If you do get a bad reaction, like within a few hours, it’s important to get help.13

Mainly, flu shots cause tiredness or a bit of pain at the shot spot. Sometimes, you might also get a slight fever. But, these reactions are usually mild and temporary.14

Yet, the flu shot is not for everyone. It might not be good for those with weak immune systems, Guillain-Barre in the past, some autoimmune diseases, or if you’re already sick.14

Flu Vaccine Recommendations

The Centers for Disease Control and Prevention (CDC) strongly suggests that anyone 6 months old or more get a flu shot each year.1 This advice is extra important for certain groups. It includes older people, kids, pregnant women, and folks with health problems.1 These folks are more likely to get very sick from the flu. So, the vaccine can help them a lot.1

CDC Guidelines

The CDC and other experts update their advice every year. They do this to make sure the flu vaccine works well.1 They use the latest info and research to choose the best protection against the flu.13

High-Risk Groups

People at high risk, like old folks, kids, pregnant women, and those with chronic diseases, should really get their flu shot.1 For them, the flu can be very dangerous. But, getting the vaccine lowers their risk of bad flu effects.1 It helps keep them healthy during flu season.1

Flu Season Preparedness

Being ready for flu season means checking how much flu is going around the country. It’s important to tell people who are more likely to get very sick from the flu to see a doctor right away if they feel sick.15 The CDC keeps a close eye on the flu, letting us know how bad it is every season.16

Monitoring Flu Activity

The CDC and groups like WHO work together to watch the flu closely. They look at how the flu is changing and how it’s affecting people.15 By doing this, they can spot new problems early, keep an eye on how well the flu shot works, and give advice to doctors and the public on time.16

Seeking Timely Medical Care

People should see a doctor as soon as they feel flu symptoms, especially when the flu is spreading a lot. This is very important for those more likely to get very sick from the flu.15 Getting early treatment with antiviral drugs can make the illness less severe and shorter, possibly keeping you out of the hospital.17 The CDC and others want to lessen how hard the flu hits people, their communities, and healthcare by telling them to get help quickly.15

Vaccine Development Process

The process to create the flu vaccine each year involves many groups working together.15 These include the World Health Organization, the FDA, and companies that make vaccines.15 Experts look at data worldwide to choose which flu strains to cover in the vaccine for the next flu season.15 They then make the vaccine, sending it off to healthcare places and drugstores.18 This happens every year to make sure the flu vaccine you get is the best it can be against the current flu types.

Strain Selection

Picking the right flu strains for the vaccine is crucial.15 Scientists keep a close eye on the flu viruses going around to figure out which ones to include.15 They share their findings with organizations like the World Health Organization and local health agencies. These groups then tell the vaccine makers the best strains to put in the vaccine.

Manufacturing and Distribution

After choosing the right strains, it’s time to make the vaccine.18 In the U.S., there are three main ways to make the flu shot. These are egg-based, cell culture-based, and recombinant vaccines.18 The egg method is the most used, but newer methods exist that don’t need eggs.18 Once the vaccines are ready, they’re sent out across the country. This way, anyone who wants one can get their flu shot.

Post-Vaccination Immunity Duration

The flu vaccine’s protection can last a few months. How long it works can vary based on your age and health.2 Getting a new shot every year is important because last year’s shot might not fully guard you.

Vaccines are better at preventing some flu viruses over others.2 Their effectiveness drops if the circulating flu viruses are not matched to what’s in the vaccine. This drop is more common as people get older.2

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Even with these details, getting vaccinated against the flu is key. Studies show it lowers the chances of getting sick by up to 60% when the vaccines match well.21 Knowing how long vaccine protection lasts helps people choose to get the shot every year and helps keep everyone healthier.


Getting a flu shot is the best way to protect yourself and others from the flu. Studies have found that the shot can lower your chances of getting sick by 40% to 60%. This is especially true if the viruses in the shot match the ones spreading around.12

In the 2019-2020 season, the flu shot is estimated to have stopped 7 million illnesses. It also prevented 3 million visits to the doctor, 100,000 hospital stays, and 7,000 deaths.12 The protection offered by the shot can change every year. But for the 2022-2023 and 2023-2024 seasons, it has been very effective at keeping people out of the hospital and from getting very sick. The risk of having to see a doctor because of the flu dropped by 40% to 60% if the shot and the viruses were a good match.12

Even though the shot can help millions every year, only about half of Americans get it.1 We still need to work hard to teach more people about the benefits of the flu shot and to encourage more people to get it. These efforts are important in keeping the flu from spreading widely and in protecting those who are most vulnerable, like older adults, young children, and those with health problems.


How effective is the flu shot this year?

A recent study found the flu shot cut the risk of serious illness by half. It also lowered hospitalizations by over a third for U.S. adults in the 2022-2023 season.

What factors influence flu vaccine effectiveness?

Flu vaccine success depends on several things. These include how well the vaccine fits the flu virus circulating that year. Also, how a person’s immune system reacts plays a role, along with the flu season’s severity.

How effective was the flu vaccine in protecting against hospitalizations in the 2022-2023 season?

During 2022-2023, the flu shot was 35% effective at preventing influenza A hospitalizations. For those 65 and older, the protection was even better at 41%.

How effective is the flu vaccine expected to be in the 2023-2024 season?

For the 2023-2024 flu season, the CDC predicts the vaccines will lower the hospitalization risk by 41% to 44% in adults. They should protect children even more, with a projected 52% to 61% reduction in severe cases.

What influenza strains are covered by the flu vaccines this season?

The 2023-2024 vaccines will guard against H1N1, H3N2, as well as the Victoria and Yamagata strains of influenza B.

How does the CDC measure flu vaccine effectiveness?

The CDC uses the Influenza Vaccine Effectiveness Networks for these studies. They look at how the vaccine performs across various groups by comparing flu rates between those who got vaccinated and those who didn’t.

How can herd immunity help protect high-risk groups?

Herd immunity means a lot of people in a community are vaccinated. This protects the most vulnerable, like seniors and kids, by making it harder for the flu to spread.

What are the recommended flu prevention measures?

Stopping the flu spread involves more than just getting the vaccine. Wash your hands often, cover your mouth when you cough or sneeze, and stay home if you’re sick.

What are the potential side effects of the flu vaccine?

The flu shot might cause a little pain, redness, or swelling where you got it. You could feel a bit feverish or achy. But remember, severe problems are very uncommon.

Who should get the flu vaccine?

Everyone over 6 months old should get the flu shot yearly. This is especially true for some groups, like seniors and those with health conditions.

How does the flu season preparedness process work?

The CDC keeps an eye on flu activity and talks about how bad it is. If you’re at high risk and feel flu symptoms, see a doctor fast. They might give you medicine that helps a lot.

How is the annual flu vaccine developed and distributed?

To create the vaccine, experts choose the most likely flu strains for the year. Global organizations work with the FDA and companies to make and deliver it.

How long does the flu vaccine’s immunity last?

The immunity you get from the flu shot might lessen over time. That’s why it’s best to get vaccinated every year. The previous year’s shot might not fully protect against the current season’s flu strains.

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