Children as young as 6 months can now receive an updated Covid-19 vaccine

(CNN) Children as young as 6 months are now eligible to receive an updated Covid-19 vaccine.

The US Food and Drug Administration on Thursday authorized updated Covid-19 vaccines from Moderna and Pfizer/BioNTech for use in children from ages 6 months through 5 years. The US Centers for Disease Control and Prevention said Friday that it had expanded use of the vaccines to that age group.

The bivalent vaccines target the original strain as well as the BA.4/5 Omicron strains. Bivalent vaccines were previously authorized as a booster for people 5 and older.

"More children now have the opportunity to update their protection against COVID-19 with a bivalent COVID-19 vaccine, and we encourage parents and caregivers of those eligible to consider doing so -- especially as we head into the holidays and winter months where more time will be spent indoors," FDA Commissioner Dr. Robert Califf said in a statement.

Not all young children are eligible to receive an updated vaccine:

• Children 6 months through 5 years who received the original, two-dose Moderna vaccine are eligible to receive a single booster of the updated bivalent Moderna vaccine two months after completing the primary vaccine series.
• Children 6 months through 4 years who haven't started their three-dose primary series of the Pfizer vaccine or received the third dose will receive the updated Pfizer vaccine as the third dose of the primary series.
• Children 6 months through 4 years who have completed the three-dose primary series of the original Pfizer vaccine are not eligible for an updated booster dose at this time.

"Children in this age group who already completed their primary series would still be expected to have protection against the most serious outcomes from the currently circulating omicron variant. The data to support giving an updated bivalent booster dose for these children are expected in January. The agency is committed to evaluating those data as quickly as possible," the FDA said in its announcement.

In general, Covid-19 vaccinations have been slow among young children. According to data from the CDC, less than 5% of children younger than 5 are fully vaccinated against the coronavirus, having completed their primary series of vaccinations. Among people 5 and older, 73% are vaccinated, and 13% are vaccinated and boosted.

The FDA authorization comes as the United States is experiencing high levels of respiratory viruses, including flu and RSV, and rising Covid-19 hospitalizations.

"COVID-19 vaccines are critical to providing ongoing protection as immunity wanes and the virus continues to mutate," the CDC said in a statement.

"Parents should talk to their child's health care provider to ensure their child is up to date on their COVID-19 and other vaccines."