The Difference Between COVID-19 and the Flu

Dr. S. George Kipa, M.D.

| 4 min read

Medical Officer

Woman blowing her nose
The 2021-2022 influenza season was considered low. Using data recorded between October 2021 and June 2022, the Centers for Disease Control and Prevention (CDC) estimated that the influenza virus infection resulted in 8 to 13 million symptomatic illnesses.
However the 2021-2022 flu season was high compared to a historically low 2020-2021 flu season; the CDC was not able to calculate the cumulative burden of flu for the 2020-2021 flu season, due to historically low numbers of flu. This outcome was partly attributed to social distancing and the mask-wearing measures in place to slow the spread of COVID-19. While there are similarities between COVID-19 and the flu, there are significant differences as well.


  • Speed of transmission: COVID-19 is considered more contagious than the flu virus, and has been observed to have more superspreading events than the flu. Additionally, if a person has COVID-19, they could be contagious for a longer time than if they had the flu.
  • Complications: While there can be complications from both the flu and COVID-19, there are differences. COVID-19, can cause blood clots in the veins and arteries of the lungs, heart or brain, as well as Multisystem Inflammatory Syndrome in children and adults. Additionally, some people may experience "long COVID" -- a range of symptoms that can last for weeks or months.
  • Treatments: While there are several antiviral therapeutic medications available to treat the flu, there is only one antiviral agent that has FDA approval to treat COVID-19.
  • Virus: COVID-19 is caused by a newly discovered strain of coronavirus, which is called SARS-COV-2. In humans, the flu is caused by two types of virus: influenza A and influenza B. There are subtypes of each. For example, H1N1 is a subtype of influenza A and was responsible for the 2009 flu pandemic.


  • At-risk populations: People most at-risk for severe illness from the flu and from COVID-19 are pregnant people, older adults and people with certain underlying medical conditions, including infants and children. However, healthy individuals can become severely sick from COVID-19.
  • Symptoms: Both COVID-19 and the flu cause many of the same respiratory disease symptoms, including fever, chills, cough, shortness of breath, sore throat, runny nose, muscle or body aches, vomiting, diarrhea, headaches and fatigue. However, COVID-19 could also cause a loss of taste or smell.
  • Transmission method: Both COVID-19 and the flu are transmitted by droplets through close contact. This can be through large and small particles containing the virus that are expelled when a person who is contagious coughs, sneezes or talks. This means the same precautions will work against both illnesses: frequent hand washing, social distancing and wearing face coverings.
  • Available vaccine: There are vaccines available for COVID-19 and the flu.

The Importance of the Flu Shot During the Pandemic

Though the flu shot will not protect individuals against COVID-19, the vaccine has many other important benefits. Having more people vaccinated against the seasonal flu will decrease the amount of people who get seriously ill from the flu this winter. As experts predict strained health care resources from new COVID-19 cases, keeping people healthy from other seasonal illnesses is especially critical.
The U.S. Centers for Disease Control and Prevention recommends flu shots for everyone ages 6 months old and up. Flu vaccination coverage among children age 6 months to 17 years was 63.8% for the 2019–2020 flu season, an increase from 62.6% in 2018–2019. The CDC estimates from the 2019-2020 flu season show that vaccination coverage increased slightly among adults from the previous season, yet disparities in flu vaccination coverage between White people and Black people and Hispanic people persisted. Flu vaccination among adults rose to 48.4%, and as is seen each flu season, coverage was higher among older adults compared with younger adults.
Each year, the flu shot helps protect individuals against the dominant strains of the flu virus that experts predict will be the most active during the fall, winter and early spring months.
Flu season typically begins in October and peaks in December and February – though cases can continue through the spring. The composition of flu vaccines has been updated. For the 2022-2023 flu season, there are three flu vaccines that are preferentially recommended for people 65 years and older. These are Fluzone High-Dose Quadrivalent vaccineFlublok Quadrivalent recombinant flu vaccine and Fluad Quadrivalent adjuvanted flu vaccine.
The recommended timing of vaccination is similar to last season. For most people who need only one dose for the season, September and October are generally good times to get vaccinated. Vaccination in July and August is not recommended for most adults but can be considered for some groups. While ideally it’s recommended to get vaccinated by the end of October, it’s important to know that vaccination after October can still provide protection during the peak of flu season.
More from
Photo credit: PeopleImages

Leave a Comment

Your email address will not be published.

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.


Blues Perspectives

Dec 6, 2021 at 6:59pm

Hi Michael. Vaccines can help protect your body from infection by building immunity to diseases like the flu, but if you are already infected then the shots will not be useful. If you want more information on the flu vaccine, you can visit: How the Flu Shot Works to Protect You - MIBluesPerspectives


Nov 13, 2021 at 7:30am

What if you have the flu and can the shots help

Blues Perspectives

Nov 23, 2020 at 6:17pm

Thanks for such a great question, Todd! We reached out to Dr. S. George Kipa, MD, deputy chief medical officer here at Blue Cross for his thoughts. This is what he had to say: "At this time, there is no rigorous scientific evidence that getting a flu shot will protect an individual from getting ill from COVID-19. Data that may provide a clear answer to elucidate this question is not yet available. The main reason to get a flu shot is to avoid getting ill with the flu and thereby decrease the strain on our health system while it is under stress from COVID-19. Influenza and COVID-19 both affect the elderly with underlying conditions. Testing in patients suspected to have either virus may rely on the same testing supplies utilize similar reagents and may lead to shortages if more people get ill with the flu. Both viruses may lead to hospitalizations and death, which could overwhelm global medical resources. While there is no rigorous scientific evidence that a flu shot will protect an individual from getting ill from COVID-19, there are theoretical grounds and early studies suggesting there may be some additional immune benefits. Both the Flu and COVID affect the lungs. Damage from flu theoretically can increase the risk to someone who gets COVID after a bout with the flu with secondary pneumonia. That adds an additional pre-existing condition to the risk profile of that patient. There are some very early suggestions that populations that were immunized for influenza may be less susceptible to testing positive for COVID, but this research is preliminary and the initial publications have not yet been peer-reviewed. More data and analysis are needed to confirm or refute these early studies. Resources:" Thank you, Candice

Todd Merz

Nov 19, 2020 at 8:39pm

There is a lot of promotion to encourage everyone to get a flu shot this season, including this article. But does Blue Cross Blue Shield know how people who have received a flu shot respond to COVID-19? Are those with a flu immunization responding better to COVID-19, worse or unknown?

MI Blues Perspectives is sponsored by Blue Cross Blue Shield of Michigan, a nonprofit, independent licensee of the Blue Cross Blue Shield Association