Researchers have said that the vaccination program against swine flu given to children provided good protection, with minimal side effects.

In a trial of over 900 children which took place during the height of the pandemic, the majority of the children responded well when given the vaccine, producing the antibodies vital to fight the infection.

The most common type of vaccine given to children was the ‘split virus’ dose, where the virus was broken down before it was administered. Another type of vaccine, the ‘whole’ virus, was given to children in two doses without a booster.

In under threes, the split version proved more effective  but in over-threes, there was a less pronounced difference in effectiveness between the two. 80% of under-3s responded to the whole vaccine, while 98% of them responded to the split vaccine. In over threes, 99% responded to the adjuvanted vaccine and 95% to the whole vaccine.

The adjuvanted vaccine was also shown to produce side effects more frequently, including fever and nausea.

The vaccination program last year focused on children, as they proved to be 4 times more likely than adults to be admitted to hospital with complications from the virus.

However there has been criticism that the World Health Organisation overstated the potential threat of swine flu, leading governments to bulk-buy vaccine doses and the anti-viral drugs Tamiflu and Relenza, which ended up unused.