Pfizer Inc and BioNTech SE on Tuesday said they have begun submitting data to US regulators seeking emergency use authorisation (EUA) of their Covid-19 vaccine for children under age five, despite weaker-than-expected immune responses in their clinical trial of two to four-year-olds.

The companies said they started the rolling submission of data following a request from the US Food and Drug Administration (FDA) in order to address an urgent public health need in the age group.