Influenza (Flu) and COVID-19 are both contagious respiratory illnesses, but they are caused by different viruses. COVID-19 is caused by infection with a new coronavirus (called SARS-CoV-2) and flu is caused by infection with influenza viruses. Because some of the symptoms of flu and COVID-19 are similar, it may be hard to tell the difference between them based on symptoms alone, and testing may be needed to help confirm a diagnosis.

To learn more about COVID-19, visit Coronavirus (COVID-19).

To learn more about flu, visit Influenza (Flu).

It is possible to have the flu, as well as other respiratory illnesses, and COVID-19 at the same time. Health experts are still studying how common this can be.

Some of the symptoms of flu and COVID-19 are similar, making it hard to tell the difference between them based on symptoms alone. Diagnostic testing can help determine if you are sick with flu or COVID-19.

Flu and COVID-19 can both result in serious illness, including illness resulting in hospitalization or death. While there is still much to learn about COVID-19, at this time, it does seem as if COVID-19 is more deadly than seasonal influenza; however, it is too early to draw any conclusions from the current data. This may change as we learn more about the number of people who are infected who have mild illnesses.

Getting a flu vaccine will not protect against COVID-19, however flu vaccination has many other important benefits. Flu vaccines have been shown to reduce the risk of flu illness, hospitalization and death. Getting a flu vaccine this fall will be more important than ever, not only to reduce your risk from flu but also to help conserve potentially scarce health care resources.

Flu viruses can change from year to year, so the vaccine is updated to protect against new virus strains that are expected to circulate in the United States. The vaccine needs to include influenza virus strains that most closely match those in circulation for the influenza season. In addition, the protection provided by the flu vaccine a person received in the previous year will diminish over time and may be too low to prevent influenza disease into next year’s flu season.

There is no change in CDC’s recommendation on timing of vaccination this flu season. Getting vaccinated in July or August is too early, especially for older people, because of the likelihood of reduced protection against flu infection later in the flu season. September and October are good times to get vaccinated. However, as long as flu viruses are circulating, vaccination should continue, even in January or later.

More information for vaccination timing this year.

Each February, before that year’s flu season ends, the FDA, the World Health Organization (WHO), the CDC, and other public health experts collaborate on collecting and reviewing data from around the world to identify the flu viruses likely to cause the most illnesses during the next flu season.

Following that process, the FDA convenes its vaccines advisory committee, consisting of outside experts, to provide advice to the FDA on the upcoming U.S. influenza season. Committee members discuss the WHO recommendations and consider which flu viruses are expected to circulate in the United States. They also review data about which flu viruses have caused illnesses in the past year, how the viruses are changing, and disease trends for the United States. The FDA takes that information into account before it selects the virus strains for FDA-licensed manufacturers to include in their vaccines for use in the United States.

The closer the match between the virus strains chosen for the vaccine and the circulating strains causing disease during flu season, the better the protection that the flu vaccine provides. Although the vaccine and viruses may not be an exact match in some years that does not mean the vaccine is not benefiting people. We know from past studies that the vaccine can still provide enough protection in people who received it to help make their illness milder or prevent flu-related complications.

To ensure that the flu vaccine is safe, effective, and of high quality, the FDA prepares and provides reagents (materials to standardize vaccines) to manufacturers that they need to make their vaccine and to verify its identity and potency. The FDA also inspects manufacturing facilities regularly and evaluates each manufacturer’s vaccine annually before it can be approved. After manufacturers have distributed their vaccines for use by the public, the FDA and CDC scientists work together to routinely evaluate reports submitted by companies, health care providers, parents, and patients to the Vaccine Adverse Event Reporting System (VAERS) of health problems that may be associated with a vaccine.

No, flu vaccines cannot cause flu illness. Flu vaccines given with a needle (i.e., flu shots) are made with either inactivated (killed) viruses, or with only a single protein from the flu virus.  The nasal spray vaccine contains live viruses that are attenuated (weakened) so that they will not cause illness.

In adults, studies have not shown a benefit from getting more than one dose of vaccine during the same influenza season, even among elderly persons with weakened immune systems. Except for children getting vaccinated for the first time, only one dose of flu vaccine is recommended each season.