evidence: From what we know, COVID-19 spreads more easily than flu. Efforts to maximize the proportion of people in the United States who are up to date with their COVID-19 vaccines remain critical to reducing the risk of severe COVID-19 illness and death. More information is available about staying up to date with COVID-19 vaccines and how well they work. Compared with flu, COVID-19 can cause more severe illness in some people. Compared to people infected with influenza virus, people infected with SARS-CoV-2 may take longer to show symptoms and may be contagious for longer periods of time. [...] While the virus that causes COVID-19 and influenza viruses are thought to spread in similar ways, the virus that causes COVID-19 is generally more contagious than influenza viruses. Also, COVID-19 has been observed to have more superspreading events than flu. This means the virus that causes COVID-19 can quickly and easily spread to a lot of people and result in continual spreading among people as time progresses.