British Prime Minister Boris Johnson said the Covid-19 vaccine developed by Oxford University and AstraZeneca is effective across all age groups, after Germany recommended the shot be given only to under-65s.

Laboratory testing found that Regeneron Pharmaceuticals Inc.’s Covid-19 antibody cocktail can combat a coronavirus variant first found in South Africa, but a similar drug from Eli Lilly and Co. is inactive against it, according to a study.

Global coronavirus cases surpassed 100 million on Jan. 27, according to a Reuters tally, as countries around the world struggle with new virus variants and vaccine shortfalls.

AstraZeneca denied the company’s Covid-19 vaccine is not very effective for people over 65 years old, after German media reports said officials fear the vaccine may not be approved in the European Union for use in the elderly.

U.S. public health officials said a second Covid-19 shot could be administered as much as six weeks apart from the first one in situations where it was not possible to get a booster dose immediately.

Pfizer slashed in half the volume of Covid-19 vaccines the company will deliver to some EU countries this week, government officials said, as frustration over the U.S. drugmaker’s unexpected cut in supplies grows.

The Covid-19 vaccine developed by Pfizer and BioNTech is likely to protect against a more infectious variant of the virus discovered in Britain which has spread around the world, according to results of further lab tests.

Previous infection with the coronavirus may offer less protection against the new variant first identified in South Africa, although scientists hope that vaccines will still work.

A new, highly transmissible variant of the coronavirus first discovered in Britain could become the dominant variant in the United States by March, the U.S. Centers for Disease Control and Prevention warned.

Britain’s medical regulator on Jan. 8 approved Moderna’s Covid-19 vaccine for use, the health ministry said, adding that it agreed to purchase an additional 10 million doses with plans for a spring rollout of the shot.