Parents who have had a child with true influenza usually recognise it as distinctly different from a common cold: the high fever that arrives suddenly rather than building over days, the child who is genuinely too unwell to get out of bed, the muscle aches and profound fatigue that are incongruous with a child who was fine the day before. The phrase "knocked sideways" is commonly used.
This matters because the management of influenza is different from cold management, the complication rate is higher, and one of the most effective preventive measures – annual influenza vaccination – is offered free on the NHS to all children aged 2-16 and is underused. Understanding what influenza is, when it warrants medical attention, and how vaccination works allows families to manage it better.
Healthbooq (healthbooq.com) covers respiratory illness and infectious disease in children.
What Influenza Is and How It Differs From a Cold
Both influenza and the common cold are caused by viruses, but the viruses are different and the clinical pictures are distinct. Influenza is caused by influenza A or B viruses. The common cold is most often caused by rhinoviruses, adenoviruses, or coronaviruses (not SARS-CoV-2 specifically, but common cold coronaviruses).
The key differences: influenza typically has an abrupt onset (well in the morning, ill by afternoon), a high fever (38.5-40 degrees or above), significant systemic features (headache, myalgia – muscle aching – and profound fatigue), and respiratory symptoms including dry cough. A cold typically has a gradual onset, a lower or absent fever, runny nose as the dominant feature, and mild systemic symptoms.
Children with influenza are frequently genuinely prostrate – lying flat, refusing to move, not interested in food or screens. This degree of illness in a child with a cold would be unusual.
Who Is at Highest Risk of Complications
Children are among the highest-risk groups for influenza-related complications compared to healthy adults. Serious complications include:
Bacterial superinfection, particularly with Streptococcus pneumoniae or Staphylococcus aureus, causing pneumonia. In some severe influenza seasons, Panton-Valentine leucocidin (PVL)-producing Staphylococcus aureus causes rapidly progressive pneumonia that can be fatal.
Febrile convulsions (fever-triggered seizures, which occur in 2-4% of children aged 6 months to 5 years during any febrile illness, but are particularly common in influenza due to the high fever).
Exacerbation of underlying respiratory conditions, particularly asthma.
Children at highest risk of severe influenza complications include: children under 2 years, children with chronic respiratory disease (asthma, bronchopulmonary dysplasia), congenital heart disease, immunocompromise, neurological conditions (cerebral palsy, epilepsy), and significant obesity. These children are eligible for antiviral treatment.
NHS Influenza Vaccination Programme
The NHS offers free annual influenza vaccination to:
All children aged 2-16 via the intranasal LAIV (live attenuated influenza vaccine, brand name Fluenz Tetra). The nasal spray vaccine is preferred for children because it produces better immune responses than injected vaccines in this age group and is more acceptable to children.
Children aged 6 months to under 2 years who have a medical risk factor (the nasal spray cannot be given to infants under 2; they receive an injected vaccine).
The LAIV contains attenuated (weakened) influenza viruses that cannot cause flu but stimulate mucosal immunity in the nasal passages as well as systemic immunity. It cannot be given to children who are severely immunocompromised or who are taking high-dose inhaled corticosteroids.
The influenza vaccine is updated annually to match the circulating strains predicted by the WHO Global Influenza Surveillance Network.
Antiviral Treatment
Oseltamivir (Tamiflu) is a neuraminidase inhibitor that reduces the severity and duration of influenza when given within 48 hours of symptom onset. In children at risk of complications, NICE recommends considering antiviral treatment even outside of formal influenza epidemics.
Most healthy children with influenza do not require antiviral treatment – the illness is self-limiting. Treatment is appropriate for: children under 2 (particularly infants under 6 months); children with risk factors for severe disease; children who are very unwell; children where the infection appears to be progressing.
When to Seek Urgent Help
Most children with influenza recover within 5-7 days with supportive care: paracetamol or ibuprofen for fever and discomfort, adequate hydration, and rest. A parent should seek urgent medical advice if the child:
Has difficulty breathing or is breathing rapidly. Has become significantly worse after initially seeming to improve (this pattern can indicate secondary bacterial pneumonia). Has a persistent fever for more than 5 days. Is under 3 months with fever. Cannot keep fluids down. Develops a rash alongside fever. Has purple or dark blotches appearing on the skin (possible meningococcal disease, which can occur alongside or independently of influenza). Is unusually difficult to rouse.
Key Takeaways
Influenza (flu) is a significant respiratory illness in children that is distinct from the common cold in its severity, speed of onset, and potential complications. Children are among the highest-risk groups for influenza complications including pneumonia, febrile convulsions, and exacerbation of asthma. The NHS offers annual free influenza vaccination to all children aged 2-16 via the nasal spray (LAIV, live attenuated influenza vaccine), and to younger children in certain risk groups. Antiviral treatment with oseltamivir (Tamiflu) is most beneficial when given within 48 hours of symptom onset and is recommended for children with risk factors. Influenza in infants under 6 months can be particularly severe and should prompt early medical assessment.
