Pfizer requested emergency approval from US health authorities to use its Covid jab in children aged five to 11.

Here is a look at different approaches to vaccinating children against the virus and the debates it has launched around the world.

What changes are made for children? Pfizer tested its jab on more than 2,000 US children aged five to 11 and submitted results to the US Food and Drug Administration (FDA) for approval.

The dosage for children in that age range is a third of what it is for adults: 0.1 mL rather than 0.3 mL.

Pfizer and BioNTech say children in trials reacted well to the vaccine and that their immune response was "robust" and "comparable" to that observed in older adolescents and young adults aged 16 to 25.

If the FDA grants authorisation when it convenes on October 26, children in that age range -- of whom there are some 28 million in the US -- could start getting vaccinated by the end of the month.

Are other countries doing this?
While many countries have begun vaccinating adolescents aged 12 and older very few have extended jabs to children younger than that.

On September 15 Cuba began administering doses of its Abdala and Soberana vaccines -- which are not approved internationally -- to children aged two to 11 years.

Also in mid-September Cambodia began vaccinating kids aged six and up with the Chinese Sinovac jab.

Sinovac has been approved for adults in more than 50 countries but before Cambodia only China had authorised its use in children over three.

Sinovac has also launched clinical trials of its jab in 14,000 children aged six months to 17 years old in Chile, Kenya, Malaysia, the Philippines and in South Africa.