The data, based on findings from a trial of more than 900 children conducted during the second wave of the 2009-10 H1N1 swine flu pandemic, could prove highly influential for policy-makers and parents in future influenza prevention and pandemic planning.
The study further highlights the importance of public participation in efforts to improve medical interventions, says one of the researchers behind the study from the University of Bristol.
Adam Finn, Professor of Paediatrics at the University of Bristol Medical School, and co-author of the study, said: “This important study was performed in record time last autumn, thanks to the many families who came forward to participate. Without people who see and understand how taking part in research helps everyone, medical advances can’t be made.”
During last year’s pandemic, children were infected at four times the rate of adults and more commonly admitted to hospital with swine flu, making them a priority group for vaccination.
The UK Department of Health purchased two H1N1 vaccines for the national immunisation programme, an adjuvanted split virion vaccine derived from egg culture and a non-adjuvanted whole virion vaccine derived from cell culture. At the time, data on the safety of and antibody responses to these vaccines were limited, and the study rapidly delivered information to government planners during the actual pandemic.
The study, published in the BMJ, is the first to be carried out comparing the immune response rates to the two vaccines in children aged between six months and 12 years.
Researchers from University Hospitals Bristol NHS Foundation Trust, working with colleagues from Exeter, Oxford, St George’s in London, Southampton and the Health Protection Agency, evaluated both vaccines in terms of their safety, tendency to cause reactions and ability to induce an antibody response.
Children were grouped by age and were randomly assigned for immunisation with either the adjuvanted split vaccine or the whole virus vaccine in two doses, 21 days apart. Data on reactions such as fever, tenderness, swelling and redness of the skin were collected for one week after each vaccination. Blood samples were also taken before vaccination and after the second dose to measure rises in antibody levels.
Both vaccines were well tolerated. However, the adjuvanted split vaccine induced a higher immune response (higher levels of antibodies in the blood) to combat the swine flu infection, especially in children aged less than three years. Significantly fewer reactions, including fever, were observed after a first dose of adjuvanted split vaccine than a second, especially in younger children.
Dr Matthew Snape of the Oxford Vaccine Group at Oxford University said: "This study is a great example of what can be achieved by researchers collaborating with each other and engaging the public in research. With funding from the National Institute of Health Research the participating sites were able to enrol over 900 children into this study in just over a month. This fantastic public response meant that we had reassuring data on the safety of these vaccines available in time to directly inform pandemic influenza immunisation policy in the UK."