It has been difficult to determine the impact of influenza infection on infants and young children, because annual outbreaks of respiratory syncytial virus infection often overlap influenza outbreaks. But careful epidemiologic tests, combined with accurate, simple-to-perform viral diagnostic studies, have now clearly demonstrated that young children--particularly those younger than 2 years--are hospitalized because of influenza at a rate that equals or exceeds the influenza hospitalization rate for the elderly.
With influenza morbidity among young children clarified, policy makers-including the American Academy of Pediatrics1-have been convinced to include children 6 to 23 months old among the high-risk groups for whom annual influenza vaccination is recommended. Yearly immunization of close contacts of children younger than 24 months is also recommended and is particularly important for contacts of those younger than 6 months because the vaccine does not provide reliable protection and is not licensed for that age group.
Implementing these recommendations will be a challenge. Children younger than 9 years who are being immunized for the first time must receive two doses separated by at least one month. All this means that, in addition to children who fall into a previously described high-risk group,* every child 6 to 23 months old must be immunized during the limited period between the time the vaccine becomes available in the fall and the onset of the influenza outbreak, and about half of those children must receive two doses separated by a month. In addition, their siblings must be immunized.
Meeting this challenge is extremely important, however. Last year the Centers for Disease Control and Prevention received voluntary reports of more than 150 childhood deaths due to influenza and of 50 children who developed influenza-related encephalopathy.
Studies have shown that far fewer than 50% of children for whom annual influenza vaccine was recommended in the past were immunized. Expanding immunization recommendations to children 6 to 23 months will, it is hoped, prompt development of notification systems that can be used to enhance the influenza immunization rate among older high-risk children as well. There is also the possibility that immunizing young children will reduce influenza transmission in the community and decrease inappropriate antibiotic use associated with respiratory viral infection.
Like other challenges, this one may also be an opportunity.
*That is, having asthma or other lung disease, heart disease, immunodeficiency, sickle cell disease, HIV infection, chronic renal disease, metabolic disease such as diabetes mellitus, or a disease requiring long-term aspirin therapy.
REFERENCE1. American Academy of Pediatrics Committee on Infectious Diseases: Recommendations for influenza immunization in children. Pediatrics2004;113:1441