Fourteen months after San Jose resident Patricia Dowd became the first person in the United States to die from COVID-19, the historic pandemic has killed more than 560,576 Americans — more fatalities than the U.S. experienced in World War I, World War II and the Korean War combined.

But Thursday, California will reach a hopeful milestone. For the first time every adult in the state will be eligible to receive a vaccine, the best defense against the pandemic. As vaccines have rolled out, the number of cases, hospitalizations and deaths in California has fallen steadily but risen lately in some other states like Michigan.

“We’re still in the midst of a pandemic and vaccines are the key to ending it more quickly,” Darrel Ng, a spokesman for the state Department of Public Health. “We continue to encourage people to take the first available vaccine.”

So what exactly changes on Thursday?

Under state rules, every Californian 16 and older will be eligible for vaccination– although some Bay Area counties such as Alameda, Santa Clara, San Francisco and Contra Costa already made the shift in recent days.

Until recently, vaccine appointments statewide were reserved for people 50 and older, health care workers, teachers, people with disabilities and other groups facing higher risks.

How do I get a vaccine?

Every Californian can sign up at myturn.ca.gov or call (833) 422-4255.

You also can contact your health care provider to make an appointment when slots become available. Many pharmacies, including Rite Aid, CVS and Walgreens also are offering appointments.

You can make an appointment through many county health websites. Or you can go to VaccineFinder.org, run by the U.S. Centers for Disease Control and Prevention, Boston Children’s Hospital and Harvard Medical School, to locate available vaccines near you.

Another useful website is Vaccinespotter.org, which scans available appointments every 1 minute at pharmacy chains across California. Users enter their ZIP Code and the distance they are willing to drive.

Will there be enough vaccines for everyone?

At first, no. California has about 32 million adults. Roughly half have received at least one dose of vaccine so far. And each week California receives about 2.5 to 3 million new doses of the vaccine from the federal government.

There will almost certainly be a big surge of interest in the first few weeks. Be patient, health experts say.

Every week, more doses are being manufactured, and more appointments are coming available.

“By the end of May, the vast majority of adult Americans will have gotten at least their first shot,” President Biden said last Tuesday.

What about kids under 16?

No vaccine has been approved yet for people younger than 16. That means about 8 million children, or roughly 20% of California’s population, are not eligible.

Clinical trials are underway, and the White House’s chief medical advisor, Dr. Anthony Fauci, said last month that the U.S. could begin vaccinating older kids against COVID-19 as soon as this fall, with younger children eligible early next year.

How much protection will vaccines give me?

Getting one shot of the Pfizer or Moderna vaccine reduces your risk of getting COVID-19 by 80% beginning two weeks after you are vaccinated, according to the CDC.

After two doses, the Pfizer and Moderna vaccines are more than 90% effective, and the Johnson & Johnson vaccine, which requires only one dose, has been found to be 72% effective in the U.S., although 100% effective in preventing death.

On Tuesday California temporarily halted distribution of the Johnson & Johnson vaccine because of a rare side effect that caused blood clots in 6 people among the 6.8 million who were vaccinated, including one death.

But state and federal officials said the change would not significantly limit vaccine supply or delay the loosening of pandemic restrictions. The Johnson & Johnson vaccines make up just 3.7% of doses administered nationwide, according to the CDC, and 7.2% of doses the federal government has delivered to California.

Didn’t I hear other rules are changing on April 15?

Yes. Under California’s color-tier system, gatherings, receptions, conferences, and indoor live events will be able to more broadly open starting Thursday. The rules are very detailed, and vary based on which tier each county is in, allowing for larger crowds if people show proof of vaccination or a negative COVID test within 72 hours. Gov. Gavin Newsom has said the state will do away with the tier system and reopen widely on June 15.  On Wednesday, the last of California’s 58 counties emerged from the most-restrictive purple tier when Merced County joined 22 other counties with substantial spread of the virus in the red tier. Most of the Bay Area is in the less-restrictive orange tier with moderate spread.

How is California doing on vaccines?

The state is making steady progress.

As of Wednesday, 51% of California’s adult population age 18 and over, or 15.6 million people, have received at least one dose of a vaccine, and 84% of Californians age 65 and over — the group most vulnerable to dying from COVID-19 — have received at least one shot, according to CDC data.

Meanwhile, about 28% of all adults in California are fully vaccinated, and 60% of those 65 and over fall into that category.

How is California doing compared to other states?

Pretty well. On Wednesday, California ranked 12th nationwide out of the 50 states by the percentage of adults over 18 with at least one dose, according to the CDC. The top state, New Hampshire, has vaccinated 66% of adults. The states with the lowest rates are Mississippi (37%), Alabama (37%), Louisiana (39%) and Tennessee (39%).

How is the U.S. doing?

The pace of vaccines has picked up considerably in recent months, and the U.S. has now vaccinated almost half of its population. That’s a higher percentage than nearly every other major nation except Israel and the United Kingdom.

The United States is currently administering about 3.3 million doses of vaccine a day, triple the pace of January. That means every five days, roughly 5% of the U.S. population is getting vaccinated.

As of Wednesday, 47.6% of Americans over age 18, or 124 million people , have received at least one dose, and 29.6% or 77 million people, were fully vaccinated.