Former U.S. Food and Drug Administration Commissioner Scott Gottlieb called for “urgent research” into a mutation of the delta variant known as delta plus following a surge in Covid-19 cases in the U.K. 

“We need urgent research to figure out if this delta plus is more transmissible, has partial immune evasion,” Gottlieb said in a tweet. 

“There’s no clear indication that it’s considerably more transmissible, but we should work to more quickly characterize these and other new variants. We have the tools.”

Gottlieb’s comments come as the U.K. reported the highest daily jump in new cases on Sunday since mid-July — around when Prime Boris Johnson authorized the removal of most Covid-related restrictions in what was dubbed “Freedom Day.” 

Weekly deaths from the virus have topped 800 for each of the past six weeks, higher than in other major western European nations, according to Bloomberg’s coronavirus tracker. To date, the U.K. has recorded almost 140,000 Covid-related fatalities.

The delta plus strain includes the K417N mutation, which has stoked concern because that’s also harbored by the beta variant that’s associated with an increased risk of reinfection.

U.K. researchers said in late June that there’s no evidence yet to suggest the additional mutation is more worrisome. A German paper out earlier this month found while both delta and delta plus infect lung cells more efficiently than the original coronavirus strain, delta plus doesn’t appear to be significantly more dangerous than delta. 

Gottlieb, who serves on Pfizer’s board of directors, led the FDA from 2017 to 2019. He has been promoting his new book, “Uncontrolled Spread: Why Covid-19 Crushed Us and How We Can Defeat the Next Pandemic.”