What to know about the flu

The flu is a contagious illness caused by any of several types of influenza viruses. The virus infects the respiratory system—the nose, throat, and lungs.

There are 4 types of influenza virus: A, B, C, and D. According to the Centers for Disease Control and Prevention (CDC), types A and B are responsible for seasonal flu epidemics.

TYPE A is the most common in adults—and often the most harmful. Subtypes of type A have caused some of the deadliest flu pandemics in history.

TYPE B is also contagious and can cause outbreaks of seasonal flu.

For more details about the influenza virus, visit the CDC website.

The flu is a potentially serious illness that can have severe, even deadly, consequences. A bout of flu may not only make you feel ill, but can end up putting you in the hospital with complications like pneumonia, even if you’re a young, healthy adult.

Your risk increases as you age, are pregnant, or if you have one or more of these conditions:

• Chronic illnesses, such as but not limited to, chronic lung disease (asthma and COPD), heart disease, diabetes, kidney disease, liver disease, or metabolic disorders
• A weakened immune system
• Body mass index (BMI) of 40 kg/m² or higher

Flu shots help your body develop immunity to flu infection. The flu shot, usually administered in your arm, triggers your immune system to get ready to fight off a future infection. Protection starts approximately 2 weeks after you get the shot.

The flu shot is different each year, as they are designed to help protect against the influenza viruses that research indicates will be most common during the upcoming season. Beginning with the 2024-2025 season, all flu vaccines in the United States are trivalent vaccines, which means they protect against three different influenza viruses: an influenza A(H1N1) virus, an influenza A(H3N2) virus, and an influenza B/Victoria virus.

In the United States, typically flu immunization season starts from fall and lasts through the winter. Flu season can last anywhere between October through May. The CDC recommends you get the flu shot before the flu season starts so that your body is fully prepared to protect you. Its never too late to get your vaccine during the flu season.

No, it’s a myth that you can get the flu from the shot. That’s because flu shots are either made with an inactive flu virus that has been killed and therefore is not infectious or developed using proteins from a flu virus that cannot cause an infection.

Because flu viruses evolve every year, last year’s vaccine may not protect you from the flu this season. Flu vaccines are updated every year with FDA-recommended strains to keep up with rapidly adapting flu viruses. When you get vaccinated, your immune system produces antibodies to help protect you from the viruses included in the vaccine. But antibody levels may decline over time—another reason to get a flu shot every year.

If you are eligible, the Centers for Disease Control and Prevention (CDC) recommends getting vaccinated against BOTH the flu and COVID-19 based on qualifying conditions.

• Remember that the COVID-19 vaccine does NOT protect you from the flu, so you will still need an annual flu shot
• As per CDC, you may be able to get your flu shot and COVID-19 vaccines at the same time

For more information, visit the CDC website.

Talk to your pharmacist or doctor about getting both shots at the same visit.

The CDC advises that you can get both vaccines at the same time if you are eligible for both. This might be more convenient than having two separate visits.

If you have an egg allergy, you may have been told in the past that you needed a certain kind of flu shot that was not made using eggs. Per the CDC, people with egg allergies may get an egg-based or non-egg-based vaccine that is appropriate for their age and health, as long as it’s given in a setting where allergic reactions can be recognized and treated quickly.

Sanofi flu studies include some of the largest and most robust ever conducted, including both clinical and real-world evidence. View them here, See the Studies.

The CDC recommends getting a flu shot while pregnant to help protect yourself and your baby from the flu.

Talk to your pharmacist or doctor to find out if Flublok^® is right for you or if you have more questions. Healthcare providers are encouraged to enroll women who receive Flublok during pregnancy in Sanofi’s vaccination pregnancy registry by calling 1-800-822-2463 or going to https://www.sanofivaccinespregnancyregistry.com.

Yes, in an analysis of data on ~15,000 pregnant individuals, including those with chronic conditions, who were exposed to Flublok during 28 days prior to conception or throughout their pregnancy. Data showed no increased risk of miscarriages or major birth defects with vaccine exposure.

The study was conducted during the 2018-2019 and 2019-2020 flu seasons and assessed specific pregnancy outcomes; not all possible impacts were assessed.

CDC recommends that breastfeeding women can get a flu shot. It is not known whether Flublok is excreted in human milk, there are no data to determine the effects of Flublok on breastfed infants or on milk production/excretion. If you are nursing you are encouraged to talk with your healthcare provider about getting vaccinated for flu. Healthcare providers are encouraged to enroll women who receive Flublok during pregnancy in Sanofi’s vaccination pregnancy registry by calling 1-800-822-2463 or going to https://www.sanofivaccinespregnancyregistry.com.

Yes. You are at a higher risk for complications due to flu because of your age. As you age, your immune system becomes less effective, making you more vulnerable to diseases like the flu. That’s why you may need more protection than a regular flu shot can offer.