California to offer vaccines to all adults from mid-April

California will make all adults eligible for Covid-19 vaccines from April 15, Governor Gavin Newsom said Thursday, as supply restrictions ease in the most populous US state.

The announcement means California -- home to some 40 million residents -- will offer access to all over-16s some two weeks ahead of President Joe Biden's May 1 deadline.

"With vaccine supply increasing and by expanding eligibility to more Californians, the light at the end of the tunnel continues to get brighter," said Newsom in a statement.

California was hit by a severe winter Covid-19 spike, and has reported the most infections and deaths of any US state -- in part due to its size -- but numbers have fallen rapidly in recent weeks, as the vaccine roll-out gathers pace.

Newsom, likely to face a rare recall election later this year, has been under pressure to reopen the state more rapidly.

From April 1, all Californians aged 50 or over will be eligible, before opening to the wider population two weeks later.

Currently, eligible individuals must be 65-plus, essential workers or suffer severe underlying health conditions, although some counties have set their own rules.

"We are even closer to putting this pandemic behind us with today's announcement and with vaccine supplies expected to increase dramatically in the months ahead," said California health secretary Mark Ghaly.

"However, we are not there yet. It will take time to vaccinate all eligible Californians. During this time, we must not let our guard down."

So far the state has administered almost 16 million vaccine doses.

California follows other states that have announced vaccine availability for all adults including Alaska, Mississippi, West Virginia, Arizona and Texas.