What Older Adults Need to Know About the Flu Vaccine

Influenza - more commonly known as the flu - is a viral infection that affects roughly 9 to 41 million people in the U.S. every year. With symptoms like muscle aches, a cough, and severe fatigue, no one wants to get sick with the flu. So it's important to do all you can to prevent catching it or spreading it, and that includes getting your annual flu vaccine.

If you're 65 years or older, your primary care provider or pharmacist may have mentioned the high-dose flu shot - or "senior flu shot" - when discussing your vaccine options. But the high-dose flu vaccine isn't the only CDC-recommended option for older adults. In fact, there's three options to choose from.

Why should older adults get a flu shot?

Older adults should get an annual flu shot because they have a greater risk of severe flu complications, including death. In fact, the CDC estimates that between 70% and 85% of flu-related deaths happen to adults 65 and older.

As you get older, your immune system has a harder time fighting off illnesses. And this makes it more likely that you'll get very sick if you come down with the flu. You're also more likely to experience serious flu-related complications, such as pneumonia (a type of lung infection).

Getting your annual flu vaccine is the best way to prevent getting sick with the flu. And if you do get sick, flu vaccines make it less likely that you'll experience severe illness or death.

Symptoms of the flu in older adults

Flu symptoms in older adults are similar to those that younger adults experience. They include:

• Fever or feeling feverish

• Cough

• Headache

• Muscle aches

• Fatigue

• Sore throat

• Runny or stuffy nose

Most flu symptoms last for about 4 to 7 days. But it's common to have lingering symptoms, such as a persistent cough, for several weeks.

Flu complications can be more serious or even life-threatening, especially for older adults. They include:

• Sinus infections

• Ear infections

• Worsening of chronic conditions, such as asthma or heart disease

• Pneumonia

• Inflammation of the heart (myocarditis)

• Brain inflammation (encephalitis)

• Muscle inflammation (myositis) or breakdown (rhabdomyolysis)

• Failure of multiple organs, such as kidney or lung failure

• Sepsis (an extreme immune response to an infection that affects many areas of the body)

What is a high-dose flu vaccine?

Compared to standard-dose vaccines, the high-dose flu vaccine contains four times the amount of antigen (the substance your immune system responds to in order to protect you from the flu). Fluzone High-Dose - currently the only high-dose flu vaccine available - is an inactivated influenza vaccine. This means it contains dead virus strains as the antigen. Because the viruses in the shot are dead, you cannot get sick with influenza from the vaccine.

Does the high-dose flu vaccine offer more protection?

Yes. In recent years, evidence has shown that high-dose flu vaccines are more effective than standard-dose vaccines for adults 65 and over. The CDC updated their flu vaccine guidelines in 2022 to reflect this. This guidance regarding high-dose flu shots has remained the same each year since those changes were made.

Are there other flu vaccines that older adults can get?

The high-dose flu vaccine isn't the only option available for older adults. The CDC also recommends the following for adults 65 and older:

• An adjuvanted vaccine: The adjuvanted flu vaccine (called Fluad) is an inactivated vaccine that contains the same amount of antigen as standard-dose vaccines. But it includes an adjuvant (a substance that causes your immune system to respond more strongly to the vaccine). The addition of an adjuvant provides a more effective immune response than standard-dose vaccines for adults 65 and older.

• A recombinant vaccine: The recombinant flu vaccine (called Flublok) includes lab-made versions of the flu viruses. It doesn't contain actual virus strains. Studies have shown that older adults respond more effectively to recombinant flu vaccines compared to standard-dose vaccines.

All three flu vaccines for older adults are trivalent, meaning they protect against three different strains of the influenza virus. The vaccine's exact composition changes every year in an effort to match the strains expected to circulate during flu season (October to May in the U.S.).

This year's flu vaccines for older adults protect against the following strains:

• Two type A influenza viruses - H1N1 and H3N2

• One type B influenza virus - Victoria lineage

Good to know: If a flu vaccine that's recommended for older adults isn't available, you can (and should) still get vaccinated with a flu vaccine that's FDA approved for your age range. All flu vaccines still offer protection. It's better to get vaccinated before flu season starts than to wait for a preferred vaccine.

What are the side effects of flu shots for older adults?

The side effects of flu shots for older adults are similar to those seen with other flu vaccines. But for Fluzone High-Dose and Fluad, side effects may happen more often compared to standard-dose vaccines.

Flu shot side effects are generally mild. Pain where the vaccine was received is the most commonly experienced side effect.

Other common side effects include:

• Muscle aches

• Headache

• Tiredness

• A general feeling of discomfort

• Redness or swelling where you received the vaccine

• Shivering

As mentioned earlier, you can't get the flu from the flu vaccine. But some people do experience flu-like symptoms after receiving it. This is expected and just means your immune system is responding to the vaccine. Symptoms should get better within about 1 to 2 days.

What ingredients are in flu vaccines for older adults?

Fluzone High-Dose and Fluad are egg-based vaccines, meaning chicken eggs were used to create the vaccine. Most people with egg allergies are still able to receive egg-based flu vaccines. But if you have an egg allergy, it's best to discuss this with a healthcare professional before getting one of these flu vaccines. Keep in mind that if you're advised to avoid them, Flublok is an egg-free option that's also recommended for adults 65 and older.

The flu vaccines for older adults may also include the following inactive ingredients to help create and stabilize the shot:

• Stabilizers: These help keep the antigen evenly distributed in the vaccine. Examples include octylphenol ethoxylate and polysorbate.

• Formaldehyde: This ingredient kills the virus during the production of Fluzone High-Dose and Fluad (the amount in the vaccine is very small and not dangerous to your health).

• Antibiotics: These help prevent bacterial contamination during vaccine production. Only trace amounts are present, and the antibiotics used are ones that most people aren't allergic to.

• Squalene: This substance is naturally found in skin oil and is used as the adjuvant in Fluad.

• Sodium chloride (saline solution): This is the liquid that the antigen is placed in to allow it to be injected.

The syringes the vaccines come in are not made with rubber latex, so they're safe for people with latex allergies to receive. The vaccines don't contain any preservatives, either.

How does the high-dose flu vaccine differ from a standard-dose vaccine?

As discussed above, Fluzone High-Dose contains four times the amount of antigen as the standard-dose flu vaccine. The influenza strains and inactive ingredients in Fluzone High-Dose are the same as Fluzone - one of the available standard-dose flu vaccines. But a few other standard-dose vaccines are available which vary more from Fluzone High-Dose.

The following are other FDA-approved flu vaccines for the 2024-2025 flu season and how they differ from the high-dose flu vaccine:

• Afluria: This is a standard-dose vaccine that is egg-based.

• Fluarix: This is a standard-dose vaccine that is egg-based.

• FluLaval: This is a standard-dose vaccine that is egg-based.

• Flucelvax: This is a standard-dose vaccine that is not egg-based, making it a safer option for people with life-threatening egg allergies.

• FluMist: This nasal spray vaccine is a live, attenuated vaccine. This means the virus is too weak to give you the flu but not completely inactivated (dead). This type of vaccine can help provide longer-lasting protection than inactivated vaccines. But it's not recommended for children under 2, adults over 50, and those with certain health conditions.

Can people under 65 get a high-dose flu vaccine?

Usually not. Fluzone High-Dose is only FDA approved for people 65 and over. So if you're younger than that, you should typically stick to the standard-dose vaccine.

One potential exception to this is if you've received a solid organ transplant. The CDC recommends that adults aged 18 to 64 who've received such transplants and are taking immune-suppressing medications may want to consider Fluzone High-Dose or Fluad. Studies suggest they may provide greater protection for this group of people.

Keep in mind that this is an off-label use of Fluzone High-Dose. You should speak with your healthcare team before getting it if you're under 65. They can help you decide which of the available flu vaccines is the best option for you.

Should you get a flu shot?

Yes! An annual flu vaccine is the best way to protect yourself and others against influenza and the complications it can cause. Flu vaccines are very safe and help lower the risk of severe illness and death due to the flu. That's why an annual flu vaccine is recommended for everyone 6 months and older, including pregnant women and people with weakened immune systems.