Nearly 400,000 doses of Johnson & Johnson's COVID-19 vaccine headed to CA

Nearly 4 million doses of Johnson & Johnson's single-dose COVID-19 vaccine are headed to states, including California, with injections expected to start as early as Tuesday.

The White House says the entire stockpile of the newly approved vaccine went out Sunday night. J&J will deliver about 16 million more doses by the end of March and 100 million total by the end of June, but the distribution would be backloaded.

According to Gov. Gavin Newsom, California is expected to receive about 380,000 doses this week.

Unlike the Moderna and Pfizer vaccines, Johnson & Johnson's shot requires only one dose and doesn't need a specialized freezer for storage, making it easier to administer.

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The U.S. Food and Drug Administration issued an emergency use authorization for the third COVID-19 vaccine developed by Johnson & Johnson.

The newest vaccine has shown to be 85% effective in preventing severe or critical illness.

At clinical trials, it has also shown to be effective against the South African and Brazilian variants.

Doctors say just because its efficacy is slightly lower than that of Moderna and Pfizer's vaccines, this is a not a second-rate vaccine.

Johnson & Johnson's CEO appeared on Good Morning America on Monday.

"We're shipping 4 million (doses) over the next several days, we then expect to have about 20 million having been delivered by March and then we'll be on this path to do 100 million by June of this year," Alex Gorsky said. "And remember that's all en route to doing almost a billion doses over the course of 2021."

How do we know the COVID-19 vaccines are safe?

Johnson & Johnson says its planning to test its vaccine on children, newborns and pregnant women soon.

Currently, there is no COVID-19 vaccine for kids.

Meanwhile, appointments are now being accepted for added groups of people who will be eligible to receive COVID-19 vaccinations at sites run by Los Angeles County starting Monday, when a massive expansion of the pool of people eligible to receive the doses goes into effect.

Beginning Monday, doses will be offered to essential workers in education and child care, food and agriculture, and law enforcement and emergency services -- but health officials said those workers will have to be patient as vaccine supplies remain limited and staff are being trained to ensure only eligible people receive shots.

The newly eligible groups include an estimated 1.2 million people in Los Angeles County.

RELATED: Los Angeles vaccination sites to expand eligibility for appointments this week

Appointments are being accepted for added groups of people who will be eligible to receive COVID-19 vaccinations at sites in Los Angeles this week.

The Associated Press and City News Service contributed to this report.