People seem to underestimate complications of the flu.

What does the CDC say?

https://www.cdc.gov/flu/symptoms/flu-vs-covid19.htm

Similarities: Both COVID-19 and flu can result in complications, including:

Pneumonia

Respiratory failure

Acute respiratory distress syndrome (fluid in the lungs)

Sepsis (a life-threatening illness caused by the body’s extreme response to an infection)

Cardiac injury (for example, heart attacks and stroke)

Multiple-organ failure (respiratory failure, kidney failure, shock)

Worsening of chronic medical conditions (involving the lungs, heart, or nervous system or diabetes)

Inflammation of the heart, brain, or muscle tissues

Secondary infections (bacterial or fungal infections that can occur in people who have already been infected with flu or COVID-19)