Influenza vs. COVID-19: The similarities and differences

With typical influenza (flu) season already beginning and COVID-19 still being spread throughout communities, this is the second year in which many families may be experiencing what was deemed last year as the “twin pandemic” of the flu and COVID-19 in their households.    

What are the similarities and differences between influenza and COVID-19 and how can they both be prevented?

Dr. Reshmi Basu, a pediatrician in the CHOC Primary Care Network, answers parents’ common questions and addresses common myths about flu and COVID-19.

What are the similarities and differences between the influenza and COVID-19 viruses?

Flu and COVID-19 are both respiratory illnesses that are caused by different viruses. The flu is caused by various types of influenza viruses, while COVID-19 is caused by SARS-CoV-2, a new coronavirus discovered in 2019, says Dr. Basu.

Compared to the flu, COVID-19 seems to be more contagious and easily spread. It can also cause more serious illnesses in some cases than the flu.

For both COVID-19 and flu, one or more days can pass between when a person becomes infected and when they begin to feel symptoms. However, it may take longer for a person to experience symptoms after being infected with COVID-19 than the flu.

Typically, a person experiences flu symptoms one to four days after infection. For COVID-19, it typically takes five days after infection for a person to experience symptoms.

In both COVID-19 and flu, it’s possible to spread the virus for at least one day before experiencing symptoms. That’s why it is so important to get tested for COVID-19 and self-quarantine immediately following potential exposure to infection.

What are the similarities and differences between COVID-19 and flu symptoms?

Both COVID-19 and flu may have symptoms ranging in severity. Kids who have been infected may show some or most of these symptoms, or they may be asymptomatic, where they don’t develop any symptoms at all. Dr. Basu points out the signs and symptoms that flu and COVID-19 have in common:

  • Fever or feeling feverish/having chills
  • Cough
  • Shortness of breath or difficulty breathing
  • Fatigue (tiredness)
  • Sore throat
  • Runny or stuffy nose
  • Muscle pain or body aches
  • Headache
  • Vomiting and diarrhea

The only major symptom that points toward COVID-19 rather than flu is the loss of smell and taste.

How do you know if your child has COVID-19 or the flu?

Since flu and COVID-19 symptoms are so similar, Dr. Basu suggests calling your pediatrician, explaining the symptoms and self-quarantining until your child can get tested for COVID-19.

Can kids get the COVID-19 vaccine and the flu shot at the same time?

Yes. Children ages 5 years and older are eligible to get the COVID-19 vaccine, and they can receive the flu shot and COVID-19 vaccine simultaneously. They can also receive any other necessary vaccines at the same time too.

The physician will administer each vaccine in a different injection site, likely in the same arm, so it’s possible that your children will experience some soreness in the injection sites. If in need of relief, give your child ibuprofen or acetaminophen to help with the pain. You can also place a cold, wet washcloth over the tender area.

Is the COVID-19 vaccine and flu shot free?

The COVID-19 vaccine is free. Appointments can be made at vaccine clinics, pharmacies, and CHOC to receive the COVID-19 vaccine. To make an appointment at CHOC, visit and enter CHOC Hospital’s zip code, 92868, to select our site.  

The flu shot is typically free with insurance at pharmacies or your pediatrician’s office. Without insurance, the flu shot can range in price from $30 to $70.  However, some pharmacies and clinics offer discounted or free flu shot promotions.

Does getting the flu vaccine give you the flu?

No. Since the flu shot is made from a dead virus, kids and adults cannot get the flu from the virus.

Some may think they have the flu because they experience some flu-like symptoms like low-grade fever or body aches following receiving the flu vaccine. However, this is actually beneficial because it shows that the body is matching the appropriate immune response to the flu shot.

Does getting the COVID-19 vaccine give you COVID-19?

No. The Pfizer vaccine, which is currently authorized for children ages 12 years and older, as well as the Moderna vaccine, which is authorized for people ages 18 years and older, is an mRNA vaccine. When the vaccine is injected, mRNA – a strip of genetic material – enters a body’s cell and prompts the cell to build copies of spike proteins. These spike proteins are the bumps that protrude from the surface of coronavirus particles. The body’s immune system then learns to spot these spike proteins and produces antibodies that block the virus from entering healthy cells in the future.

Because of this, the Pfizer and Moderna COVID-19 vaccines may cause some symptoms like a low-grade fever, body aches and tiredness. Like the flu vaccine, this is good because it shows that the immune system is initiating an appropriate immune response to the vaccine.

Johnson and Johnson’s Janssen vaccine is a viral vector, which uses a modified version of a different virus to deliver important instructions to cells. The viral vector is not the COVID-19 virus, but a different, harmless virus that will produce a spike protein that the body will create an immune response to. That immune response will then protect the body if it comes in contact with COVID-19.

Learn more about the COVID-19 vaccine and kids.

How can you help prevent your kids from getting the flu or COVID-19?

Having your children get the flu shot as soon as possible will help avoid serious illness from the flu. Children as young as 6 months of age are recommended to receive the flu shot. For healthy children ages 2 years and older, a nasal spray vaccination is also available. Speak with your pediatrician about whether they recommend the nasal spray vaccination for your child. 

Since the primary flu season is from October to April, it’s best to get the flu shot before or during October. However, getting the flu shot later in flu season is much better than not getting it at all.

For protection against COVID-19, have your eligible children, ages 5 years and older, receive the COVID-19 vaccine. Not only will it significantly decrease the chances of your children contracting the virus, but it will also decrease the chances of them becoming seriously ill with the virus. Additionally, vaccinating as many members of your family as possible will help the community spread and offer your family a much lesser chance of contracting the virus. 

Get ready for flu season with a visit to the pediatrician for the flu shot and wellness checks.