By April 19, all 50 states ware due to have expanded COVID-19 vaccine eligibility to everyone 16 and over. It comes as variants continue to spread and new variants keep popping up.

The average new COVID-19 case count is up more than 16% in the U.S. over the past two weeks. The Centers for Disease Control and Prevention say part of the reason for the rise is variants.

Experts say the spread of variants are particularly concerning because there are still many questions about them.

"To date we don't know that the variants have completely escaped immunity, where for example, if you've been naturally infected or immunized you still may be hospitalized or in an ICU or die," says Dr. Paul Offit, member of the FDA Vaccine Advisory Committee.

And other variants are popping up, like one first identified in India, which has also been reported in California. That's not to mention variants still to come as the virus mutates over time.

Still, doctors all agree that vaccinations are our best bet.

"We really do have to hunker down for a few more weeks," says Dr. Ashish Jha, dean of the Brown University School of Public Health.