Editor’s note: The Covid-19 Vaccine Frequently Asked Questions page has been retired. Updated information regarding Covid-19 vaccination may be found at the NEJM Covid-19 Vaccine Resource Center.

A 13-year-old girl in Canada became so sick with H5N1, or bird flu, in late 2024 that she had to be put on a ventilator.

Four years have passed since the global outbreak of the COVID-19 pandemic ... According to the "New England Journal of Medicine," this was not a small group. Nearly 113,000 people were surveyed.