The European Medicines Agency said on Thursday it "recommended granting an extension of indication for the Covid vaccine Comirnaty to include use in children aged five to 11".
Millions of schoolchildren across Europe are now in line for the jab as a new Covid wave hits the continent.
The World Health Organisation (WHO) warned on Tuesday Europe could see deaths exceed two million by March unless urgent measures are taken.
Doctors in the Austrian capital of Vienna had already begun vaccinating the age group ahead of the regulator’s decision, as the country is faced with spiking infection rates.
The regulator’s approval still needs to be rubber stamped by the European Commission before EU states can officially begin giving out doses to the age group.
It should be given in two doses of ten micrograms three weeks apart as an injection, said the regulator. Adult doses are 30 micrograms.
Even with the smaller jab, children who are five to 11 years old developed antibody levels as strong as teenagers and young adults getting the regular-strength vaccines, Pfizer said in September.
Studies on Pfizer's vaccine in children have not been big enough to detect any rare side effects from the second dose, like the chest and heart inflammation seen in mostly male older teenagers and young adults.
Earlier this week, German health minister Jens Spahn said shipping of vaccines for younger children in the EU would begin on December 20.
Although children mostly only get mild symptoms, some experts believe vaccinating them should be a priority to reduce the virus's spread.
However, the WHO has appealed to rich countries to prioritise donating doses to poor countries who have yet to give a first dose to vulnerable people.