A paediatric GP explains how the nasal spray and injected flu vaccines work differently, and why age, asthma and medical history can affect which one a child receives.
As flu season approaches, many parents are familiar with the annual question of why a child is offered a nasal spray rather than an injection. According to NHS GP Shruti Nathwani, the answer is not simply about making the appointment less daunting. The two vaccines protect against influenza in different ways, and age and medical history help determine which one is most appropriate.
Nathwani, a GP with specialist paediatric training who posts as @thechildrensmedic on Instagram, explained that the nasal spray is designed to build immunity where the virus usually enters the body: the lining of the nose. That helps trigger local protection as well as antibody and T-cell responses elsewhere. The injection, by contrast, mainly prompts the body to produce antibodies in the blood. Both approaches can protect children, but they do so through slightly different immune pathways.
The child’s age matters too. Nathwani said babies aged six to 23 months are given the injection rather than the nasal spray because clinical trials in that group found a higher rate of wheezing and hospital admission linked to the spray. That distinction matches guidance from the US Centres for Disease Control and Prevention, which says the nasal spray vaccine is intended for healthy people aged two through 49 and is not recommended for younger children or others in specific higher-risk groups.
The nasal vaccine is a live attenuated vaccine, meaning it contains weakened virus rather than the illness itself. Nathwani stressed that it is not the same as catching flu, and that the virus is adapted to work in the cooler environment of the nose. She also said asthma does not automatically rule out the spray, but children with active wheezing, those who have needed extra reliever inhaler use in the previous 72 hours, or some with severe asthma may be steered towards the injection instead. The UK guidance has also changed so that egg allergy is no longer considered a reason to avoid the spray, although parents should still tell the vaccination team about any allergies before the appointment.
Parents are usually told to watch for mild, short-lived side effects such as a reduced appetite, runny nose, headache or tiredness. NHS Inform says these effects are generally brief and may last for less than a week. Nathwani added that, although transmission to other people is very unlikely, families should mention it if the child lives with or has close contact with someone who is severely immunocompromised. The NHS and other health authorities also list several groups who should not receive the spray, including children under two, those with a serious allergy to a previous dose or to ingredients such as gelatine, neomycin or gentamicin, and some children with weakened immune systems or certain asthma-related concerns.
Disclaimer: This content is for informational purposes only and is not intended to be a substitute for professional medical judgment, advice, diagnosis, or treatment.
