Washington DC - The US drug regulator has missed a deadline for granting full approval to Novavax's Covid-19 vaccine, the company said Wednesday, amid major shakeups at health agencies under President Donald Trump.

In a document sent to the financial markets regulator and seen by AFP, US drugmaker Novavax said it was still awaiting a response from the Food and Drug Administration (FDA), which had been promised to make a decision by April 1.

"As of Tuesday, April 1, we had responded to all of the FDA's information requests," Novavax said in the filing, adding it believes its vaccine is ready for approval.

"As of today, we continue to wait on action from the agency and have not yet received an official decision from the US FDA," it added.

The company is seeking full approval of its Covid-19 vaccine, which is already authorized in the US through an emergency use procedure for people aged 12 and over.

According to the Wall Street Journal, which first reported the delay, the authorization is being blocked by FDA officials, who are reportedly requesting "more data."

Politico described the action as "a highly unusual step."

Contacted by AFP, the FDA did not immediately respond.

The delay comes amid a major overhaul of health agencies, spearheaded by Trump's health secretary Robert F. Kennedy Jr., a noted vaccine skeptic.

Mass layoffs began at the major US health agencies on Tuesday as the Trump administration embarks on a major restructuring that will cut 10,000 jobs.

Unlike the mRNA Covid-19 vaccines from Pfizer-BioNTech and Moderna, the Novavax vaccine uses a more conventional technology, similar to that of the whooping cough vaccine.