LOS ANGELES -- California, the most populous state in the United States, opened up COVID-19 vaccine appointments to all aged 16 and older on Thursday.

"Safe, free, and effective COVID-19 vaccines are now available to everyone age 16 and up," according to the latest version of the state's COVID-19 vaccine scheduling tool My Turn.

"Let's end this pandemic," said California public health officials on the page, urging residents to check for available appointments and book their vaccination as soon as possible.

California Governor Gavin Newsom noted on Twitter Thursday morning that nearly 50 percent of eligible Californians have been vaccinated so far.

"We've administered 24 million doses -- over 8 million more than any other state. We have the lowest positivity rate in the country," Newsom added.

The western U.S. state, home to around 40 million residents, had expanded vaccine eligibility to people aged 50 and older, starting April 1.

California paused the use of Johnson & Johnson COVID-19 vaccine in accordance with recommendations from two federal health agencies on Tuesday. State officials noted that the move would not significantly impact vaccination allocations, since in the state less than 4 percent of vaccine allocation this week involves Johnson & Johnson vaccine.

California is one of the hardest-hit states in the country. It has seen more than 3.6 million cases and 59,000 deaths from the pandemic as of Wednesday, both the highest in the country so far.

New COVID-19 cases, deaths and hospitalizations have continued to decline in California in recent weeks. Newsom announced earlier this month that the state plans to fully reopen by June 15, if COVID-19 vaccinations remain widely available and hospitalizations associated with the virus stay low.