As the more contagious variant of omicron spreads across the state, health care workers in California will be required to undergo a booster injection of the coronavirus to ensure that hospitals are prepared to respond to a surge in cases.

Governor Gavin Newson announced the order on his personal Twitter account on Tuesday and plans to provide more details at a news conference on Wednesday.

California has already required healthcare workers to be vaccinated against the coronavirus. The directive took effect in September and has since resulted in the dismissal or suspension of thousands of people. Now it will join New Mexico as at least the second state to require booster injections for medical staff.

Last week, Newsom issued the first statewide shutdown order in March 2020. He warned that cases may increase and re-implemented a rule requiring everyone to wear masks when gathering in public rooms.

The concern stems from the rise of omicron, which as of Monday is the main variant of the US coronavirus. As cold temperatures keep people indoors, the Midwest and Northeast have seen the largest increase in the number of cases and hospitalizations.

Much of the content about this variant is still unknown, including whether it will cause more or less serious illness. Scientists say that omicron spreads more easily than other coronavirus strains (including delta). Early studies have shown that people who are vaccinated need a third injection to get the best chance of preventing infection, but even without an additional dose, vaccination should still provide strong protection against serious illness and death.

So far, California has fared better than many other states. The U.S. Centers for Disease Control and Prevention lists California as a place where the virus is “highly” spread, as well as almost every other place in the country. But last week, California had an average of 114 new cases per 100,000 people, less than half of the national level.

Although 70% of Californians are fully vaccinated, 30% (that is, approximately 12 million people) have not yet been vaccinated. The California Department of Public Health stated that unvaccinated people are 7 times more likely to be infected with the coronavirus, nearly 13 times more likely to be hospitalized, and nearly 16 times more likely to die from the coronavirus.

The number of hospitalizations related to the coronavirus in California has been slowly rising, increasing by 15% in the past 11 days to 3,852. This is less than one-fifth of what it was before the late summer peak and a year ago before the vaccine was widely used.

However, although hospitals generally had fewer patients than last winter, many hospitals have fewer staff to treat patients. The shortage of personnel is because it is difficult for companies to find workers, including hospitals. A recent study by the University of California, San Francisco estimated that the state’s nursing shortage may continue until 2026.