Infants and young children could soon receive an updated COVID-19 vaccine as part of their three-dose series.

Pfizer Inc. on Monday asked the U.S. Food and Drug Administration to have the vaccine that targets the Omicron subvariants BA.4 and BA.5 replace the third dose in the series for children aged 6 months through 4 years old. Children in that age group would still receive two doses of the original COVID vaccine prior to the Omicron-targeted dose.

Though children aged 5 and up and adults need only two doses to complete a primary series, younger children need three doses, CNN reported.

“With the high level of respiratory illnesses currently circulating among children under 5 years of age, updated COVID-19 vaccines may help prevent severe illness and hospitalization,” the company said in a news release.

It is unknown whether parents will choose to get the third shot for their children even if it’s approved.

Fewer than 5% of children younger than 5 have been fully vaccinated for COVID, according to the U.S. Centers for Disease Control and Prevention. Uptake is higher in children aged 5 and older, 73% of whom are vaccinated and 13% of whom have also received boosters, CNN reported.

Meanwhile respiratory illnesses are surging for this population, including COVID-19 cases, flu and another virus known as RSV (respiratory syncytial virus).

No vaccine exists for RSV, but public health officials have urged Americans to get COVID boosters and flu shots.

U.S. Health and Human Services Secretary Xavier Becerra said in a Friday letter to U.S. governors that respiratory viruses are “increasing strain” on the country’s health care systems, CNN reported.

The Biden administration “stands ready to continue assisting you with resources, supplies and personnel,” Becerra told the governors.

More information

The U.S. Centers for Disease Control and Prevention has more on protecting children from COVID-19.