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