Sarah Hyland of "Modern Family" has had multiple kidney transplants. That means she's immunocompromised because of the anti-rejection drugs she has to take and because her original condition strains her immune system.

When she got her COVID-19 vaccine in March, she declared, "HALLELUJAH! I AM FINALLY VACCINATED!!!!!"

Now she sounds like a candidate for a booster shot, which is recommended for anyone who's moderately or severely immunocompromised.

Unfortunately, many people don't know if their health challenges mean they should get a booster shot.

Here are the Centers for Disease Control and Prevention's guidelines and definitions of moderately to severely immunocompromised, plus why it's important to act now.

1. Get a booster that's the same brand — Moderna or Pfizer — you got originally.

2. Wait at least 28 days after your second injection before getting a booster.

3. You qualify as immunocompromised if:

• You've been receiving cancer treatment for a solid or blood cancer. 

• You’ve had an organ transplant and are taking immune-suppressing medication.

• You’ve received a stem cell transplant within the past two years.

• You are diagnosed with moderate or severe primary immunodeficiency.

• You have an advanced or untreated HIV infection.

• You are being treated with high-dose corticosteroids or any other immune-suppressing medications. 

4. The booster increases your resistance to COVID-19 to a more robust level of effectiveness. And if you do contract COVID-19, the booster may help reduce the severity of symptoms.

Don't compromise your health if you're immunocompromised. Check with your doctor about a booster today.