The UK, controversially at the time, spaced them out further which could lead to a stronger and more durable immune response, say experts.
The increase in cases will not be an equal threat to all European countries.
“The half-term break may have played a part, though infections were decreasing prior to this time.
It is too soon though to tell if the declines in cases among the over 80s are due to extra protection from boosting or less Covid circulating due to half term school holidays.