The COVID-19 Delta variant, which was first identified in India, is becoming the dominant variant globally because of its significantly increased transmissibility, WHO chief scientist Soumya Swaminathan said on Friday.

According to the COVID-19 Weekly Epidemiological Update issued by the WHO on June 15, the Delta variant is now being reported in about 80 countries around the world. Another 12 countries and areas are ‘reporting the detection of B.1.617 without further specification of lineage at this time.’

The B.1.617.2 Delta variant was first detected in India around October 2020.

“The whole situation is so dynamic because of the variants that are now circulating and…the Delta variant is well on its way to becoming the dominant variant globally because of its significantly increased transmissibility,” Swaminathan said responding to a question at a press briefing in Geneva on Friday.

Her remarks came hours after Public Health England (PHE) said that the number of Delta variant infections has jumped by 33,630 in a week to hit a total of 75,953 in the UK, with the highly transmissible variant now making up 99 per cent of all COVID-19 cases in the country.

In Washington, the Centres for Disease Control and Prevention (CDC) Director Rochelle Walensky said she expects the Delta variant will become the dominant coronavirus strain in the United States.

“As worrisome as this delta strain is with regard to its hyper transmissibility, our vaccines work,” Walensky told ABC News on Friday.

In Geneva, Swaminathan said there is a need for more data from well-designed studies on the efficacy of the different vaccines that are in use in different countries against the different variants.

Swaminathan added that there has to be in place a study that uses a good design, or a randomised trial or studies during the rollout of a vaccine in a country to see what happens when people have one dose of the vaccine or two doses of the vaccine and see how many are getting infected and are ending up hospitalised and getting seriously ill.

“This is something that we are watching very carefully and documenting and we now have a special expert group that’s been set up to exactly track the performance of vaccines and their effectiveness when used at the population level in relation to the variants.

“This also means that countries need to do sequencing, side by side with documenting vaccine effectiveness. We need to expand sequencing,” she said, adding that through this information, experts can start getting some solid and robust evidence on vaccine performance.