The Food and Drug Administration on Tuesday authorized an additional dose of Pfizer and Moderna‘s Covid-19 vaccines targeting the omicron variant for seniors and people with weak immune systems.

Seniors who are 65 years of age or older and who have already received a vaccine targeting the omicron BA.5 subvariant are now eligible to receive another dose at least four months after their last shot, according to the FDA. People with weak immune systems can receive another omicron shot at least two months after their last dose and receive additional shots at the discretion of their doctor.

Children 6 months through 5 years of age who are unvaccinated can now receive the full two-dose series of Moderna’s omicron vaccine. Kids 6 months through 4 years of age can receive three doses of Pfizer’s shot that targets omicron.

Children who are 5 years old can receive either two doses of Moderna or a single dose of Pfizer.

Children under age 5 who have already started their vaccination series with the old Covid vaccines that target the original strain of the virus can receive the omicron shots to finish their course, though how many doses they receive will depend on whether they took Pfizer or Moderna vaccines.

Although the burden of the pandemic has eased substantially, Covid continues to kill more than 1,300 people per week, according to the Centers for Disease Control and Prevention. Some 1,600 people are still hospitalized with Covid daily on average, according to the public health agency.

“Covid-19 continues to be a very real risk for many people, and we encourage individuals to consider staying current with vaccination, including with a bivalent Covid-19 vaccine,” said Dr. Peter Marks, who heads the FDA department responsible for vaccines.

The FDA first authorized the omicron BA.5 shots last August, but that subvariant has long since been displaced by a version of omicron called XBB.1.5. In June, the agency will likely update the variant that the Covid vaccines target, ahead of the fall respiratory virus season.