"Prof Anthony Harnden, deputy chairman of the JCVI, says all over-50s will be vaccinated within the next few weeks.
He told BBC Breakfast: "In primary care, we're still vaccinating cohort six - all with underlying illness - and some of seven.
"But, throughout the country, we're going down to cohort nine.
"Most people over the age of 50 will be vaccinated really within the next few weeks - so it is tremendously successful.
"Those first nine priority groups included 99% of all hospitalisations and deaths, certainly in wave one of the pandemic, so we're feeling very optimistic.
"We're seeing a very sharp reduction in the deaths and hospitalisations throughout the country.""