Professor Keith Willett, NHS England's medical director for acute care, says in a statement: "Flu can be spread more easily by children, especially to vulnerable relatives such as older grandparents, those with heart or lung conditions and pregnant family members.
"With less than a month until family gatherings over the festive season, there's still time for parents to get their 'super-spreader' children vaccinated to help protect elderly relatives over Christmas and before the flu season traditionally reaches its peak."
Flu is more severe than a winter cold and can lead to serious complications, increasing the risk of death in older people and other vulnerable groups such as people with asthma, pregnant women and those with heart, lung and liver problems.
Latest figures from the Office for National Statistics (ONS) show that 34,300 people died last winter because of cold weather and circulating viral infections, including flu. The figures account for 20.9% extra deaths in winter compared to those in the other seasons.
Could the NHS cope?
Doctors and health bosses have warned that a major outbreak of flu this winter could overwhelm the NHS.
Last winter there were 400,000 additional visits to accident and emergency (A&E) departments between November and February – an increase of 5.6% on the previous year.
In winter, hospital admissions for people with respiratory problems double, from 1,000 to 2,000 each day. Around a third of all extra winter deaths are due to respiratory illnesses.
Last month, the Society for Acute Medicine warned that a major flu outbreak could lead to hospitals being forced to cancel all non-emergency operations for several months. Dr Nick Scriven, the society's president, said frontline staff were sceptical that adequate preparations are being made to keep the health system functioning and felt there was "nothing new this year other than crossed fingers".
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