Every year, millions of people get the flu. The good news is you can reduce your risk by half with an annual flu vaccination. For National Immunization Month, we’re answering some of the most frequently asked questions about flu shots as fall approaches.

At what age should  I start getting an annual flu shot?
The recommended age to start receiving an annual flu vaccination is 6 months, according to the Centers for Disease Control and Prevention (CDC). Children between the ages of 6 months and 8 years may require two doses spaced at least four weeks apart when they receive their first flu shot. Following that, they can receive a single dose of the vaccine annually.

Who most needs to get a flu shot?
Everyone benefits from vaccination, but an annual flu shot is especially important for people who have a greater risk of influenza complications. This includes children under the age of 2, adults over the age of 50, people who are pregnant or plan to be, individuals with a body mass index of 40 or higher and people with chronic illnesses. Conditions that increase your risk of complications include:

  • Asthma
  • Cancer
  • Chronic obstructive pulmonary  disease (COPD)
  • Heart disease
  • Cystic fibrosis
  • Diabetes
  • Brain or nervous system conditions
  • HIV
  • Kidney or liver disease

Are there any side effects to the vaccine? 
Common side effects include soreness, redness or swelling where the shot was given. The flu vaccine also can cause headache, fever, nausea, muscle aches and fatigue. This is usually the effect of your body producing protective antibodies—not the vaccine itself giving you the flu, which is a common misconception.

When is the best time to get a flu shot?
The flu shot is usually available at the end of August, and flu season reaches its peak around December and February. It takes up to two weeks to build immunity, and the shot is effective for around three to six months. It’s usually best to get vaccinated by the end of October. However, if you miss that window, you can still benefit from getting a vaccine even after flu season is in full swing.

Why do I need to get vaccinated for the flu every year?
There are several types of influenza strains, and they change quickly. The vaccine is designed annually to protect against the varieties predicted to be the most common in that flu season. Last year’s vaccine may not be effective against the flu viruses that are prevalent this year. Also, vaccines function by causing your immune system to make antibodies that protect you from those viruses. Your antibody levels decline over time, so getting a flu shot annually boosts your immune response.

What kind of protection does the  flu vaccine offer?
The effectiveness of the flu vaccine can  vary. It is generally most effective among people under the age of 65. For healthy adults between the ages of 18 and 64, the vaccine is about 50% effective, according to the Mayo Clinic. For people 65 and older, they may develop less immunity after receiving vaccination. High-dose flu vaccines can help improve the immune response of this population.

What happens if I get the flu anyway?
There are a few reasons why you may get the flu even if you are vaccinated. You may be exposed to the virus during the  two-week window when immunity builds, or you might encounter a variant of influenza that the vaccine was not designed to protect against. However, your flu shot can help reduce the severity of the illness. Research has shown that vaccinated adults who are hospitalized with the flu spend less time in the hospital and are around 60% less likely to require treatment in the intensive care unit, according to the CDC.

How else can I lower my risk of getting the flu?
Getting your flu shot is the best protection against the flu, but other steps you can  take include:

  • Washing your hands often and thoroughly, or using hand sanitizer
  • Avoiding touching your eyes, nose or mouth
  • Staying out of close contact with others who are sick
  • Regularly cleaning commonly touched surfaces, such as counters,  light switches and doorknobs
  • Exercising regularly
  • Getting enough sleep
  • Drinking enough fluids, and eating a healthy diet

Sources: CDC, Mayo Clinic