According to data released Tuesday by the Centers for Disease Control and Prevention, the more transmissible Delta Covid-19 strain was responsible for more than half the coronavirus cases in America between June 20 and July 3.

POLITICO was informed by a spokesperson for the CDC that surveillance data showed that the Delta variant rose from 30.4 percent to cases in the two-week period ended June 19th to 51.7 percent between June 20th and July 3.

This sharp rise highlights the extent of the Delta variant’s spread across the country, and raises questions about the Biden administration’s plans to control it at the national scale. According to new CDC projections, the Delta strain was responsible for more than 80 percent cases in Iowa, Kansas and Missouri between June 20th and July 3.

The administration is trying to improve the vaccination rates in some states, including those in the south. Although the number of vaccines administered has increased slightly over the past few days, overall vaccination rates have remained stagnant. According to CDC data, approximately 55 percent of Americans aged 12 and over are fully vaccinated.

Rochelle Walensky, Director of the CDC, warned last week about the dangers of the Delta variant to unvaccinated people. She also said that it could surpass the Covid-19 Alpha variant within the next few weeks. Walensky stated that it was clear that communities in which people are not vaccinated are at risk, stating that she had surveyed every state and country.

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Biden officials continue to point out data showing that vaccines from Johnson & Johnson, Moderna, and Pfizer are effective in protecting against the variant and preventing severe diseases. For months, the administration has been consistent in its message about the Delta variant: Get vaccinated.

But early research from Israel released by the country’s health ministry on Monday appears to suggest the Pfizer-BioNTech vaccine is less effective against the Delta variant. However, early research released Monday by Israel’s health ministry suggests that the Pfizer BioNTech vaccine is less effective against this variant.} The vaccine’s effectiveness against infection and symptomatic illnesses fell to 64 percent, while its efficacy against serious illness and hospitalization remained at 93 percent.