Prime Minister Boris Johnson said on Friday that the U.K. would ramp up its vaccination program to slow the spread of a SARS CoV-2 variant first spotted in India. 

Johnson said that the variant could interfere with plans to scale back COVID-19 health measures originally enacted last year. 

Scientists still like substantive data to understand how it compares to other lineages, but many experts including U.K.’s chief medical officer, Chris Whitty, suspect it is more transmissible. 

Whitty said: “Earlier this week we said that we thought that it was as transmissible as B.1.1.7 and possibly even more so,” Witty said, referring to the variant first identified in the U.K. “There is now confidence … that this variant [from India] is more transmissible than B.1.1.7.”

The variant has fueled a substantial number of infections in India, which is now grappling with more than 400,000 infections. 

Johnson said the Indian variant could “pose a serious disruption” to the U.K.’s reopening plans. 

The U.K. has had one of the most aggressive vaccination programs in the world, with nearly 70% of adults receiving at least one vaccine dose.