https://www.mercurynews.com/2021/08/06/q-a-what-we-know-about-covids-delta-plus-variant-boosters-and-the-end-of-the-surge/

There are two major reasons why we’re struggling with a summer surge of COVID-19: not enough Californians are vaccinated and the new delta variant is much more contagious than earlier strains.

But other challenges also are upending the pandemic landscape. With help from experts, we answer questions about the field’s fast-moving science.