The COVID-19 Delta variant — the highly transmissible strain — continues to spread throughout the country. Pennsylvania, however, remains one of the most protected states, given its high vaccination rate. Erika Fry and Nicolas Rapp reported the statewide level of protection for Fortune.

So far, studies have shown that vaccines are effective against this variant. The news about the variant, therefore, becomes pertinent to those eschewing vaccination. They are now highly susceptible to the Delta strain.

The biological offshoot of the coronavirus currently represents 13.1 percent of all new cases in Pennsylvania and the surrounding region.

Unfortunately, the number of unimmunized Americans remains stubbornly high, despite abundant vaccine supplies.

Through June 22, at least one shot of the COVID-19 vaccine was administered to 177.9 million U.S. citizens (53.6 percent of the population). Moreover, 150.8 million people have received both doses.

The look at state-by-state rates, however, reveals disparities.

Pennsylvania has one of the highest rates of vaccinated adults (74.7 percent).

Read more about current vaccination rates in Fortune.