In the largest population-based study of its type in the US, over 45,000 infants aged 6-23 months, who received inactivated influenza vaccine between 1991 and 2003 were included. Medically attended events after flu vaccination were reviewed for 4 different time periods, and compared with 2 control time periods. All diagnostic codes were checked.
This study showed that there were very few medically attended events and none were for serious causes associated with the vaccine. None of the 14 diagnoses made in the context of medical referral after vaccination had any statistically significant link to vaccination.
The study provides additional evidence supporting the safety of flu vaccination in children aged 6-23 months.
Rates of seasonal flu are usually high amongst children: 20-30% of the overall population of children and up to 50% of children in daycare contract flu every year. Children with cardiac, respiratory and neurological diseases have a high risk of severe flu and flu-related mortality. Despite low overall mortality rates in the general population of children, it is important to remember that up to half the cases of flu-related mortality occur in children who were previously healthy. Most children hospitalized because of flu are aged under 1 year (annual hospitalization rate: 10-100 out of every 10,000 children depending on influenza season and geographic region). Hospitalization rates amongst kindergarten age children are similar to those seen amongst the elderly.