The U.S. Centers for Disease Control and Prevention (CDC) issued updated guidelines for people with underlying medical conditions who want to get vaccinated.

In the guidelines posted Saturday, the CDC said, “Adults of any age with certain underlying medical conditions are at increased risk for severe illness from the virus that causes COVID-19. mRNA [messenger RNA] COVID-19 vaccines may be administered to people with underlying medical conditions provided they have not had a severe allergic reaction to any of the ingredients in the vaccine.”

Both Pfizer and Moderna vaccines are mRNA-based.

The CDC has also provided specific COVID vaccine information for people who have HIV, weakened immune systems, and autoimmune diseases such as Guillain-Barre Syndrome (GBS) and Bell’s palsy.

The agency said people with HIV and weakened immune systems “may receive a COVID-19 vaccine. However, they should be aware of the limited safety data.”

Currently, there is no information available about the safety of the vaccines for people with weakened immune systems, according to the CDC. People with HIV were included in clinical trials, but “safety data specific to this group are not yet available at this time,” the agency said.

On December 17, the U.S. Food and Drug Administration (FDA) said cases of Bell’s palsy, or facial paralysis, were reported in some volunteers who received the Pfizer and Moderna vaccines in clinical trials.

However, the new CDC guidelines said the FDA “does not consider these to be above the rate expected in the general population. They have not concluded these cases were caused by vaccination. Therefore, persons who have previously had Bell’s palsy may receive an mRNA COVID-19 vaccine.”

Experts have said the vaccines have been found safe for people with GBS, an autoimmune disorder in which the body’s immune system attacks its own nerves, according to the CDC.

The health agency said, “To date, no cases of Guillain-Barre syndrome (GBS) have been reported following vaccination among participants in the mRNA COVID-19 vaccine clinical trials.”

“With few exceptions, the independent Advisory Committee on Immunization Practices (ACIP) general best practice guidelines for immunization do not include a history of GBS as a precaution to vaccination with other vaccines,” it added.

Since the pandemic began, health officials have been warning that people with certain comorbidities are at an increased risk of developing serious COVID-19 illness. The article was published in Medscape Medical News.