A 60-year-old recovering from breast cancer, Paris resident Nadine Roger is at high-risk from Covid-19 and wants to get vaccinated as soon as possible. Yet when she was offered the vaccine manufactured by AstraZeneca she turned it down.

"The AstraZeneca (shot) frightens me," she said. Roger, a medical technician, said she would wait instead for the shot made by US firm Johnson & Johnson, which has not yet been approved by European regulators...