The study demonstrated that Delta infection resulted in similarly high SARS-CoV-2 viral loads in vaccinated and unvaccinated people, said CDC Director Rochelle Walensky.

“High viral loads suggest an increased risk of transmission and raised concern that, unlike with other variants, vaccinated people infected with Delta can transmit the virus,” she said.

“Israel is a pioneer in going ahead with the third dose for older people of the age of 60 and above. The fight against the COVID pandemic is global. The only way we can defeat COVID is together,” Bennett said. The booster campaign, with shots administered by health maintenance organizations, will effectively turn Israel into a testing ground for a third dose before approval by the U.S. Food and Drug Administration (FDA).

Germany now requires a negative test or proof of immunity only from those arriving from so-called “risk areas”, “high-incidence areas” and “virus-variant areas”, which in Europe now include Britain, Spain and the Netherlands.

Rules are now also applied differently at airports and road crossings, and regional leaders are keen to make them more consistent.