People eligible to be vaccinated against flu are being urged to have the jab.
Latest figures show more than a third of people aged over 65 in the Wakefield district have not had their free vaccination so far this winter.
And just 40 per cent of pregnant women and working-age people with underlying medical conditions have had the flu jab.
Health bosses have warned that some people can develop conditions like bronchitis and pneumonia and end up in hospital if they get flu.
It can also lead to death for some at-risk people.
Dr Andrew Furber, the district’s director of public health, said: “You may think if you were vaccinated last year that you’re covered, but you actually need a flu jab each winter to be protected.
“It can be passed from people who don’t even have the symptoms. It is important for us to remain vigilant and take all the necessary precautions to protect those who are more vulnerable. Contact your GP surgery and make an appointment.”
Old people, young children, pregnant women and people with conditions including COPD, heart disease and asthma are classed as at risk from flu.
For more information about the flu jab, click here