In Los Angeles County, 100% of all cases sequenced in April were omicron with its two more infectious offshoots gaining ground.
"These new subvariants of omicron are even more infectious than sort of their parent variants or the first omicron and also people are letting their guard down," said California state epidemiologist Dr. Eric Pan.
Public health authorities reporting the number of students and staff testing positive at K-12 schools in L.A. County increased for the fifth consecutive week. And while LAUSD board members voted not to implement a student vaccine mandate for a year, officials are strongly urging vaccines and boosters for all who are eligible.
"As a parent, and actually I'm a pediatric infectious disease specialist. I'm very confident that these vaccines are safe and they're effective," Pan said.
Moderna confirmed its latest application for emergency use authorization is complete. Under review will be vaccines for those 17 and under including children 6 months to 6 years old. An FDA advisory committee is set to review the data.
Growing proportion of COVID deaths occurring among vaccinated: ABC News analysis
"My understanding is they may be discussing that in June so we're hoping that soon after that," Pan said.
Hospitalizations nationwide are at their highest levels since March. Officials in Northern California voiced their concern.
"What we're seeing now is similar to what we were seeing in mid February, and it's more than what we were seeing at the height of the Delta surge.," said Dr. Sara Cody, Santa Clara County's public health officer.
Dr. Anthony Fauci, chief medical advisor to President Biden, testified before Congress. Lawmakers asked him about what Americans can expect in the fall with variant-specific boosters.
"I think sometime in the middle of the summer, we're going to know what the cadence is going to be about how often we're going to have to vaccinate," Fauci said.
Fauci added that the pandemic won't end with a declaration saying it's over, but he expects a slow step down to an endemic phase.
He did acknowledge that a growing number of vaccinated people are dying of COVID, but he said many of them were already at increased risk. He also said waning immunity and people not getting boosted also plays a role.