The government’s chief medical adviser has insisted that cost-cutting was not to blame for the decision not to vaccinate all under-fives against flu.

The parents of three-year-old Lana Ameen, who died from swine flu days after Christmas, have called for a national programme to protect the youngest children.

But chief medical officer Professor Dame Sally Davies insisted that people of working age were in fact at greatest risk of being killed by the strains of flu prevalent in the UK this winter and it was important for health professionals to focus on protecting the most vulnerable.

She urged people in at-risk groups - such as those with underlying medical complaints - to get themselves vaccinated, warning that more than half of those aged under 65 have so far got the jab to which they are entitled.

Her comments came as she wrote to all GPs and NHS trusts to remind them of the danger of potentially lethal secondary infections piggy-backing on the flu virus.

Challenged over whether it was time for all young children to be vaccinated, Prof Davies said that the bulk of the 112 verified deaths from flu since September had come among the working-age population, with just six under-fives and 16 over-65s.

“This isn’t about cost-cutting,” she told Sky News. “This is about focusing our efforts on those who are most at risk.

“The data from the pandemic last year showed - and this year’s data is very similar - that if you are in an at-risk group you are 18 times more likely to die of flu if you catch it than a healthy person, so we need to focus on getting those at risk to come forward and have vaccinations.”

After earlier complaints that the failure to advertise flu jabs had led to low take-up rates this winter, Prof Davies said that vaccination rates were now at normal levels for the time of year.

But she said that only 70% of eligible over-65s and 46% of at-risk patients below that age had so far been vaccinated.

“That means over half of the people at risk in the young children and working age groups are not coming forward for vaccination,” she said.

Prof Davies said that the flu virus made sufferers more vulnerable to other infections which could prove fatal, and confirmed that she had written to health professionals to remind them of the danger.

“It is a threat every winter with seasonal flu,” she said. “People can die directly from flu affecting their lungs and making their lungs not work properly, but many of the deaths relate to bacteria infecting their lungs when they are weak.

“It is not abnormal, but we are seeing quite a high rate. They may have started with these bacterial infections and then got flu, or they may acquire those infections. Doctors need to be aware to give the right antibiotics.”