The Centre for Adverse Reactions Monitoring has seen an increase in reported adverse reactions to this year's seasonal flu vaccine.
The centre's director told the Health Select Committee on Wednesday that there has been a massive uptake of the flu vaccination this year.
Dr Michael Tatley said children are taking the vaccine more than in previous years and the reported reactions are those common in children.
Dr Tatley said the centre has received about 200 reports of adverse reactions to the Gardisil vaccination - which is given to teenagers to prevent human papillomavirus.
He said about 6% of all hospital admissions are from adverse reactions to medicines, but research indicates that only 10% of reactions are actually reported.