While attention has been focused on the threat from the Delta variant, which is now dominant in Britain and France as well as the United States, scientists are also concerned about the Beta variant because clinical trials of vaccines are showing that they offer less protection against it. The Beta variant was first identified in South Africa in December.
The presence of Beta in France remains relatively low, according to GISAID, an international open source database; it accounts for 3.4 percent of new cases over the past four weeks.
Some research has shown that the AstraZeneca-Oxford vaccine, the backbone of Britain’s inoculation campaign, has been less effective in preventing mild and moderate Beta cases. In February, South Africa halted use of the vaccine over those concerns.
In France, concerns that the Delta variant, which accounts for about half of the country’s new cases, could unleash a fourth wave of the virus prompted President Emmanuel Macron this week to announce new vaccination requirements. They include mandatory inoculations for health care workers and proof of immunization or a recent negative test to enter restaurants and cultural venues.
Mr. Macron’s announcement came just three days after nightclubs reopened for the first time in 16 months, which many believed had signaled the completion of France’s protracted efforts to emerge from the pandemic. But the new measures dashed hopes of a return to a prepandemic normal and of a smooth summer vacation season.