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Questions and answers - Childhood flu vaccine

Childhood influenza frequently asked questions

Influenza, commonly called ‘the flu’ is a contagious respiratory viral illness that can cause serious illness and even death in young children, older adults and certain vulnerable people of all ages
The symptoms include fever, headache, muscle aches, tiredness and weakness, congestion in the nose, throat and lungs. Children may have nausea, vomiting and diarrhea. In more serious infections, complications can occur such as pneumonia, inflammation of the heart, and inflammation of the lungs and the illness may last much longer. Healthy children under 5 years of age are more likely than adults to be hospitalized

Each year is different. Attack rates vary from 5% to 20% in the general community but can be 2-3 times higher in households (1). Even in “non-severe” seasons flu is an important cause of disease in the community

Influenza is spread through the air when someone with the disease coughs, sneezes or even talks. This releases droplets from the nose or throat that contain the influenza virus. The influenza virus can also be spread when someone touches something that has the virus on it, and then touches their nose, eyes or mouth

If we look at illness by 5 year age groups in Australia, we find that the highest rate of flu occurs in the 0-4 year group (2)
This age group is more likely than any other to present to Emergency Departments and GPs and to need hospitalization (3). Recent data shows children under 2 have between a 2 and 5% chance of admission to hospital each year with influenza.
This age group is more likely than any other to develop secondary bacterial infections, such as pneumonia (3)
Flu can kill; in WA in 2007, three deaths occurred as a result of flu in children under the age of 4. In the United States sentinel system there have been over 100 childhood deaths this year.
Children are a major source of flu transmission to others in the community

Good nutrition and general health are important in maintaining an efficient immune system
Good respiratory hygiene (washing hands frequently, covering the mouth when sneezing, using and disposing of tissues, etc) all help to reduce the risk of catching or spreading the flu
A vaccine is available, which significantly reduces the risk of getting flu. This is an important component of prevention because flu is a highly contagious and potentially dangerous disease

The vaccine is safe and well-tolerated in healthy children
The side effects of vaccination are usually minor and include fever and local reaction. Fever occurs in 10-35% of children under 2 (4); local reactions (swelling, redness, pain) occur in about 10% and muscle aches may occur and may last up to two days
Children who have a severe allergy to eggs (anaphylaxis) should not receive the flu vaccine

The effectiveness of the vaccine varies a little from year to year, depending on how well the vaccine matches the virus for that year
The effectiveness also depends on the age and the strength of the immune system of the child
Despite these variations the vaccine has been shown to have an efficacy of 59% in children aged 2-16 years in one study (5) and CDC in the USA has just announced a 75% efficacy in their childhood vaccination program for influenza where children received two doses of vaccine. These data were for the age group 6 months to 2 years and were collected across two US winters.(6)

The vaccines currently available in Australia are either split or subunit vaccines, prepared from killed influenza virus. They cannot cause the flu

Children <9 years of age who have not been vaccinated previously are recommended to receive 2 doses the first year they get vaccinated. In subsequent years, they only need one dose. This is because many children <9 years have not been infected with influenza viruses previously, and a booster dose is needed in children previously not exposed to influenza infections or vaccine in order for them to have a good immune response

Vaccination needs to be given every year because the flu virus constantly mutates. Only one dose of vaccine is required in the second and subsequent years

Nicholson KG. Clinical features of influenza. Seminars in Respiratory Infections 1992;7:26-37
Australian Policy and Surveillance Section, Australian Influenza Report No 13, week ending 13 October 2007.
Heikkinen T, Booy R, Campins M, Finn A. Should healthy children be vaccinated against influenza? A consensus report of the Summits of Independent European Vaccination Experts. Eur J Pediatr: 165:223-228, 2006.
American Academy of Pediatrics Committee on Infectious Diseases. Prevention of influenza: recommendations for influenza immunization of children, 2006-2007. Pediatrics 2007; 119 (4):846-51.
Smith S, Demicheli V, Di Pietrantonj C, Harnden AR, Jefferson T, Matheson NJ, Rivetti A. Vaccines for preventing influenza in healthy children (Review). Cochrane Database of Systematic Reviews 2006, Issue 1. Art. No.:CD004879. DOI:10.1002/14651858.CD0048790.pub2
Centers for Disease Control and Prevention Press Release. CDC’s Advisory Committee Recommends Influenza Vaccination for Children 6 months through 18 years of age http://www.cdc.gov/od/oc/media/pressrel/2008/r080227.htm (External link)