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.