Flu shot: Effectiveness, importance, and where to get it - Insider

• Flu shots are the safest and most effective way to protect yourself from the influenza virus. 
• The best time to get a flu shot is in October, so it will last through the entirety of flu season. 
• A study found that those who got a flu shot were less likely to develop severe COVID-19 complications. 

It's more important than ever to get a flu shot this year, with experts warning of a "twindemic" — a potentially deadly combination of COVID-19 and influenza viruses. 

While being vaccinated against the flu won't totally protect you from COVID-19, it will help prevent you and others from getting sick, which could save lives and help lessen the burden on our healthcare system.

Here's everything you need to know to get your flu shot this year and why it's so vital. 

Important: A 2021 study found that those who got a flu shot in the previous six months were also less likely to develop serious complications from COVID-19. 

The flu basics

Influenza — or the flu — is a viral infection that affects the respiratory system. The seasonal flu, appearing in the winter months in the Northern Hemisphere, is a very common and highly contagious illness. 

The most common symptoms of the flu include: 

Getting a flu shot each year can protect yourself from experiencing these symptoms, or at least reduce their severity. In fact, during the 2018-19 flu season, the vaccine prevented 4.4 million influenza illnesses, 58,000 influenza-related hospitalizations, and 3,500 deaths due to influenza. 

How the flu vaccine works 

Flu shots work by helping your body develop antibodies that can protect you from being infected with an influenza virus. Most flu vaccines are referred to as quadrivalent because they protect you from four different types of flu: two influenza A viruses and two influenza B viruses. 

The flu vaccine is made up of several virus strains, called candidate vaccine viruses (CVVs), that vary by year. There are two ways the flu vaccines can be administered:

• Injection. The flu shot is most commonly given through an injection with a syringe, usually in the deltoid muscle of your upper arm. For injections, the CVVs are inactivated, meaning they will help your immune system produce antibodies without giving you the actual flu virus. 
• Nasal spray. This vaccine, inhaled through your nose, is often preferable for those who do not like injections. However, it may not be as effective as a flu shot, according to a 2019 study. In addition, for nasal sprays, the CVVs are live but weakened. While it is approved and recommended for those between the age of 2 and 49 years old, it should not be taken by high-risk groups, such as children under the age of 2 or people with pre-existing health conditions.

Why the flu shot is important

"Many people skip their flu shot thinking it doesn't matter, but an estimated 80% of children who died from the flu did not get their flu vaccine," says Alice Benjamin, APRN, MSN, ACNS-BC, FNP-C, a Los Angeles-based clinical nurse specialist and family nurse practitioner. "In adults, getting an annual flu shot has been shown to decrease your chances of falling seriously sick with the flu by 40% to 60%."

Overall, the flu shot is the most effective way to prevent yourself from getting the flu. That doesn't mean it's 100% effective — according to CDC data from February 2020, the flu shot was about 46% effective for the 2019-20 season. But that also shouldn't stop you from getting one. 

"Let's acknowledge that the flu vaccine is not perfect," says William Schaffner, MD, a professor of preventive medicine and infectious diseases at the Vanderbilt University Medical Center. "But it's the best flu vaccine that modern science can give us. And we can do a lot of good with our pretty good vaccine."

By protecting you from getting sick, flu shots also help protect you from more severe health complications. For example, studies have found that heart attacks and strokes may be more likely to occur soon after you have the flu. 

"If you need another reason to get protection from a flu shot, that's it," Schaffner says.

If you're still not convinced, it may be helpful to weigh the pros and cons of getting a flu shot:

Getting a flu shot is easy and affordable, and it brings many health benefits with few risks.

Yuqing Liu/Insider

Flu vaccine side effects 

There are a few common side effects from the flu shot injection, such as:

• Muscle soreness, redness, or swelling at the site of injection
• Headache
• Nausea or stomach pain

However, these side effects are quite mild, and shouldn't last longer than a few days after you get your flu shot. If you get the nasal spray vaccine, you may also experience a runny nose or sore throat. 

Note: Getting a flu shot will not give you the flu. You can still get the flu after getting a flu shot, but the symptoms likely won't be as severe as they would have been without the vaccine. 

Who should get a flu vaccine?

Everyone who is at least six months old should get a flu shot every year. It's especially important for high-risk groups, such as health care providers, caregivers, and people who are immunocompromised or have chronic medical conditions such as asthma or diabetes.

The following groups should also get flu shots, though there may be certain precautions you should be aware of: 

Infants 

If your infant is six months old or older, they can and should get a flu shot. Children younger than two years old are at especially high risk of developing serious complications if they get the flu.

Infants getting their first flu vaccine or who have only received one dose of the vaccine need to get two injections at least four weeks apart. The CDC recommends that the second dose be administered at the end of October.

Kids 

As with infants, children eight years old and younger who are getting their first flu vaccine or have only received one dose of the vaccine will need two injections at least four weeks apart. 

Children who are at least two years old can also get the vaccine administered via a nasal spray. However, the nasal spray flu vaccine should not be given to children two to four years old who have asthma , or to children 2 to 17 years old who are taking medications that contain aspirin or salicylate.

Seniors 

Because your immune system weakens as you age, and becomes less effective at producing antibodies to fight off infections, two special types of flu shots are available for people over the age of 65.

One is a high-dose vaccine called Fluzone, which you can get wherever most flu shots are available. The other is FLUAD, which is an adjuvanted flu vaccine. This means it promotes a better response by your immune system. 

Pregnant people 

If you're pregnant, your weakened immune system makes you more at risk of flu complications. It's important to get a flu shot to protect yourself as well as your baby. The vaccine's flu-fighting antibodies pass through your placenta and will continue to protect your baby for six months.

It's safe to get a flu shot during any trimester, as well as when you're breastfeeding. However, pregnant women should not get the nasal spray flu vaccine because it contains a live virus that could enter your placenta and infect the fetus.

Who should not get a flu shot? 

Children younger than six months old and people with certain health conditions should not get a flu shot, the CDC advises.

These health conditions include:

• A severe allergic reaction to a previous flu shot. According to a 2016 study, for every one million flu shots given, there were about 1.3 severe allergic reactions, such as tongue or throat swelling, shortness of breath, or vomiting.
• Egg allergies. Although the most common flu vaccine contains viruses grown in eggs, people with mild allergic symptoms like hives can safely get it, according to the CDC. If you have a severe allergy, two egg-free flu vaccines are available. You can also get a regular flu shot as long as it's in a medical setting such as a doctor's office or clinic, and is supervised by a health care provider who can treat an anaphylactic reaction.
• A fever. If you have a fever over 99.5°F, you might want to wait to get a flu shot. Your immune system is already producing antibodies to fight infection, so the vaccine may not be as effective. However, if you have a cold with no fever, it's safe to get a flu shot.
• Guillain-Barré syndrome (GBS). This is a rare neurological disorder that causes your immune system to damage your nerve cells. Its exact cause is unknown, but it often develops after a respiratory illness or the flu. It is very rare to get GBS after a flu shot, according to the CDC. If you already have GBS, talk to your doctor before getting a flu shot.

If you can't get a flu shot, there are other steps you can take to prevent the flu. "When you know the flu is in your community, that's the time to really hunker down," Schaffner says. Wash your hands frequently, practice social distancing, and avoid people who are coughing or sneezing. 

When to get a flu shot 

"October is the golden month to be vaccinated," Schaffner says. This will help protect you throughout the entire flu season, which in the Northern Hemisphere generally lasts from October to March, peaking in February. 

If you don't get vaccinated in October, you should still get vaccinated while flu shots are available. Flu shots are usually available from late September to late February. 

Getting vaccinated early, like in July or August, is not recommended by the CDC, especially for older adults. The flu shot's effectiveness will likely wear off – it only lasts about six months — giving you less protection later in the flu season.  

Where to get a flu shot 

Flu shots are widely available at your doctor's office, pharmacies like CVS or Walgreens, and many other locations. Here's how to get one in three simple steps. 

How to get your flu shot in 3 easy steps 

1. Find a flu shot location nearby. In addition to your doctor's office, you can get a flu shot at drugstores like CVS and Walgreens, and at pharmacies in major retailers such as Walmart and Costco. You can find a location near you by visiting VaccineFinder.
2. Check your insurance. If you have health insurance, your flu shot will be free. If you don't have insurance, some employers and colleges offer free flu shots. Your county health department may also provide free shots, especially for seniors.
3. Make sure you bring ID.  When you go to get your flu shot, bring your health insurance ID card, if you have one. You may need to also show your driver's license or other ID.

Video: Flu myths 

Insider's takeaway

It's always important to get a flu shot, and it's essential during the COVID-19 pandemic. Overall, getting a flu shot helps prevent you — as well as the people close to you — from getting sick, needing medical care, or being admitted to a hospital. 

Laura Goldman

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