As the COVID-19 virus evolves, so will vaccine guidelines.

One thing that’s been clear from the start is that immunocompromised people have a high risk of severe and prolonged COVID-19 infections. And those with a weakened immune system are especially vulnerable to the highly contagious delta variant making its rounds through the U.S., even if they are vaccinated – 44% of all breakthrough cases that lead to hospitalization are among this group despite making up just 2.7% of the population. This is why the FDA and CDC recently recommended that people who are moderately to severely immunocompromised receive a third vaccine dose to bolster their protection.

To learn more about why a third dose is necessary for immunocompromised people, we asked physician scientist Jonathan Golob of the University of Michigan to explain what conditions can result in a weakened immune system, and how immunocompromised people can best protect themselves from COVID-19.

Also today:

Vivian Lam

Assistant Health + Medicine Editor

Cancer and organ transplant patients, people with untreated HIV and people with other immunodeficiencies are at high risk of severe COVID-19 infection. burakkarademir/E+ via Getty Images

Immunocompromised people make up nearly half of COVID-19 breakthrough hospitalizations – an extra vaccine dose may help

Jonathan Golob, University of Michigan

People with weakened immune systems are at a high risk of severe and prolonged COVID-19 infections. An extra vaccine dose can bolster protection.

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