The Food and Drug Administration (FDA) said Friday that it is working “around the clock” to authorize COVID-19 vaccines for children under 12, but that it cannot offer a specific timeline for when they will be available.

The lengthy statement from acting FDA Commissioner Janet Woodcock and top vaccine official Peter Marks comes as the agency is facing pressure to move quickly on the issue, given that COVID-19 vaccines are currently unavailable for children under 12.

The FDA sought to address the pressure in Friday’s statement, but also emphasized that it would “follow the science.”

“Just like you, we are eager to see our children and grandchildren vaccinated against COVID-19 as soon as possible,” Woodcock and Marks said. “We have to let the science and data guide us.”

“This process is complex and relies on robust manufacturer trials and data, and while we cannot offer a specific date or timeline for when it may be completed for the various manufacturers’ vaccine candidates, we can assure the public we are working as expeditiously as possible to meet this critical public health need and we very much hope to have pediatric COVID-19 vaccines available in the coming months,” they added.