(WPRI) — New data out of Israel shows the efficacy of Pfizer’s COVID-19 vaccine has dropped by around 30%, down to 64%.

The data released by Israel’s Health Ministry shows during May, when the Delta COVID-19 strain was less prevalent, the vaccine was 94.3% effective.

The variant, which is believed to be twice as contagious as the original strain of COVID-19, is thought to be responsible for 90% of new cases in Israel over the past two weeks.

Israel is now working on promoting two studies related to the Pfizer vaccine — one will examine the effectiveness of the vaccine over time in both various age groups and states of health, while the other will examine cellular immunity over time.

The U.S. Centers for Disease Control and Prevention (CDC) says an estimated one in four cases in the U.S. involves the more contagious variant.

CDC Director Dr. Rochelle Walensky said Thursday approximately 1,000 counties in the country have vaccination coverage of less than 30%, causing major concerns about the spread of the Delta variant in primarily the Southeast and Midwest.

“In some of these areas we are already seeing increasing rates of disease as the Delta variant continues to spread across the country. We expect to see increased transmission in these communities unless we can vaccinate more people now,” Walensky said.

The R.I. Department of Health last reported nine cases of the Delta variant in the state, and last week reported the state was back up to showing “moderate transmission” of the virus.

The rate of new cases per 100,000 persons last week increased to 10.9. To be considered low transmission, the rate of new cases per 100,000 persons over a seven-day period must be below ten.

The same week the transmission of the virus ticked up, Rhode Island became the fifth state to reach 70% of adults fully vaccinated, joining Massachusetts, Connecticut, Vermont and Maine.

“The big thing for us, though, is there’s still a tremendous amount of work to be done, while we cross that 70% threshold for adults, there’s still a lot of Rhode Islanders that need to get vaccinated, especially before we head into the fall,” Tom McCarthy, executive director of the state’s COVID-19 response, said.

According to Friday’s data, roughly 691,500 Rhode Islanders have received at least their first dose, while more than 633,000 are now considered fully vaccinated.