Omicron variant of Covid-19 or how well they will protect against severe illness. Lab tests are under way to determine vaccine efficacy against Omicron with results expected within weeks.
In the meantime the Delta variant remains dominant and experts, governments and vaccine makers are urging people to take advantage of booster jabs where they are available.
Delta has proved able to evade vaccine defences against transmission better than the Alpha, Beta and Gamma Covid variants. But jabs have remained highly effective at preventing severe illness from Delta, lowering the risk of overwhelming hospital resources.