Health experts have urged people to make sure they avoid taking unnecessary risks and have the seasonal flu jab, after figures show fewer people have been vaccinated this year.
The Department of Health said that confusion over the swine flu component of this year’s jab could be behind the slower uptake.
At the end of October only 48% of over-65s had received the injection, which is 7% lower than at the same point in 2009.
Just over a quarter of under-65s in the at-risk categories - including those with diabetes, heart disease, asthma and pregnant women - had decided to have the preventative treatment, compared with 31% 12 months ago.
Ministers have said the “blip” could be due to “unnecessary” fears about the jab also containing protection against the swine flu strain.
Last year, there was some concern among the public about the safety of the vaccine.
People who had the swine flu vaccine last year are still covered against the strain this year, but the latest seasonal flu vaccine also protects against two other strains of flu.
Professor David Salisbury, director of immunisation at the Department of Health, said: “We don’t know how serious flu will be this winter.
“But we do know that improving seasonal flu vaccine uptake will ensure that more vulnerable people are protected.
“This year’s vaccine is the ordinary seasonal flu jab and protects against the dominant strains.
“This year it protects against three types of flu, including the type known as swine flu.
“It is vital we don’t underestimate the effects of this virus. It is not the same as getting a cold and it can seriously affect your health.