A US regulatory health agency on Thursday approved a booster dose for children between the ages of 5 and 11.
The Food and Drug Administration (FDA) said it hopes the third dose will help increase the young population's protection against Covid-19 while the US is currently seeing a rise in cases.
"While it has largely been the case that Covid-19 tends to be less severe in children than adults, the Omicron wave has seen more kids getting sick with the disease and being hospitalised," FDA Commissioner Robert Califf said in a statement.
"Children may also experience longer term effects, even following initially mild disease."
Next in the process, before children can get immunised, the US Centres for Disease Control and Prevention (CDC) will decide if it will formally recommend the additional vaccine dose. The agency often follows FDA approval but it need not.
A study from the CDC in April found that at least 75 per cent of US children have had coronavirus.
The country is seeing a rise in cases and hospital admittances from Omicron subvariants that are more contagious than the original Omicron variant that swept the country in the winter.
American parents are still awaiting approval for children under the age of 5 to get vaccinated against Covid-19.