Influenza is a minor problem for pediatricians compared with our associates in internal medicine. It fills both of our offices and wards and we each try to get high-risk patients immunized each fall, but from mere on, our work is different. Most of our influenza-related admissions are for bronchiolitis or asthma, croup, or febrile seizures, or to rule out sepsis. We see mild viral pneumonia, but, fortunately, severe primary influenza or secondary bacterial pneumonia and death are rare in children. More than 85% of our pediatrie admissions lack chronic diseases for which immunization is recommended.1
In contrast, most adults admitted for influenza-related disease have a chronic disease, and as many as 5% to 10% will die. Most influenza deaths (90%) occur in those 65 years or older,2 although high admission and death rates occur for adults younger than mis with chronic diseases. Death rates can be much higher during pandemics.
Children help influenza epidemics and pandemics get under way.1 The evidence for this includes that school-age children almost always have the highest attack rates for influenza, sometimes as high as 75% during one season. High school students, children in day care, and working adults follow in attack rates. Further, disease rates peak first in children during an outbreak. Disease generally strikes adults at high risk during the second half of an outbreak, and infection rates are lower although severe disease is much more common.
Second, schools seem to facilitate the infection of children.1 The initiation of influenza outbreaks usually coincides with the start of school. The first cases appeared in lhe spring before the 1918 and the 1957 pandemics, but the real outbreaks did not begin until schools opened in the fall. The 1968 pandemic was by far the mildest of the three in the 20th century. The fact that the school holiday break began just as influenza was getting rolling that year is offered as one reason for this.1 Attack rates dropped suddenly after school let out for Christmas, and ended up more equally dispersed among ages than is usually the case. It looked like separating these students stopped the spread of virus.
Third is the way influenza uniquely allows children to spread its virus. Influenza hits adults hard and fast. In contrast, children are less sick so they can be up and around, spreading the agent to other children and eventually to adults.
In summary, children seem to acquire influenza virus in school or day care and carry it to their homes and communities.
THE NEXT PANDEMIC
Many believe the question is not whether another pandemic will hit, but when, and it is unlikely we will have much warning. At least 6 months are needed to produce large amounts of a new vaccine. Another 3 or more months must be added to distribute it, administer it, and get effective immune responses. There is considerable concern about disease during this lag.3 The game will be a race to get effective immunization to those at high risk before the outbreak involves mem.1
In Pandemic Influenza: A Planning Guide for State and Local Officials, the Centers for Disease Control and Prevention (CDC) recommends that the first vaccine should go to those at high risk.3 Universal immunization will occur as vaccine becomes available.
An alternative would be to immunize school-age children first in an attempt to slow the outbreak until the high-risk populalion can be immunized.' This may make sense in view of the role chilthen play in spreading this virus.
Another delaying strategy would be to close schools for a week or so at the point when cases are starting to rise rapidly among school-age children. This would give time for communicability to end before children were back in school and strive for what seemed to happen during Christmas break in 1968.
The CDC Planning Guide mentions closing schools, but with little emphasis. It does, however, encourage local planning. Pediatricians working with state and local health departments may help promote and time appropriate school closings. We will be among the first to see an influx of young febrile children positive for influenza A.
CURRENT PREVENTION FAILURES
Excess mortality from influenza epidemics remains substantial.4 From 1972 to 1984, an average of 15,542 annual excess deaths were ascribed to influenza. During the next 8 years, this rose to 29,900 per year, and this rate has probably continued at this level through 1997, despite modem critical care and record doses of influenza vaccine.
One pmblem is compliance. How effective are you at getting all children with chronic health conditions into your office each fall to receive vaccine? Immunization rates are also relatively low for high-risk adults, at 66% for those 65 years and older, 38% for those 50 to 64 years, and 20%+ for those 20 to 49 years in a 1997 study.5 Pneumococcal vaccine compliance is even lower.
Another significant problem is that influenza vaccine is considered less effective for seniors. One study found that 61% of 200 elderly adults admitted with proven influenza A infection were up to date for this vaccine.3
SHIFTING POLICY FOR INFLUENZA IMMUNIZATION
Should annual influenza vaccine be routine for all school-age and preschool children older than 6 months - or maybe for everybody? This question is being asked because what we are doing is less than perfect and children play a role in spreading outbreaks.1,4
Immunization policy is broadening.2 The latest recommendations advise adding immunization for those 50 to 64 years old high risk or not) after others at risk have had a chance to be immunized. All health care workers should be immunized annually to prevent the spread of virus to and from our patients and keep us at work during epidemics. Further, the CDC now recommends that contacts of high-risk individuals should be immunized. This is even more difficult than getting high-risk children immunized, but a study just published found that immunization of children in day care reduced influenza among household contacts substantially.6
Finally, the CDC now indicates mat all who want vaccine may receive it if available late in the immunization season this year. All this resembles stepping stones toward broader, perhaps universal, immunization some day- a policy that would reduce the spread of influenza virus by children.
What has prevented universal immunization up to now? We give a lot of shots already. Another each year might even decrease compliance for other vaccines mat children need. Also, is it ethical to give children annual inactivated influenza injections to reduce morbidity and mortality rates of older individuals? Putting this as protecting Grandpa and Grandma might help, but it is hard to see how this would be acceptable unless parents want them given.
However, we are forgetting about the cold attenuated vaccine that should be available soon. This vaccine will make immunization of children much easier.
1. Glezen WP. Emerging infections: pandemic influenza. Epidemial Rev. 1996; 18:64-76.
2. Updated recommendations from the Advisory Committee on Immunization Practices in response to delays in supply of influenza vaccine for the 2000-01 season. MMWR. 2000;49:888892. Available at: www.cdc.gov/ mmwr/ preview / mm wrh t ml/ mm4939a3.htm.
3. National Vaccine Program Office. Pandemic Influenza: A Planning Guide for Siate and Local Officials (Draft 2.1). Atlanta, GA: Centers for Disease Control and Prevention; 2000:1-20. Available at: www.cdc.gov/od/ nvpo / pandemicflu .htm.
4. Glezen WP. Influenza control: unfinished business. /AMA. 1999;261:944945.
5. Singleton JA, Greby SM, Wooten KG, et al. Influenza, pneumococcal, and tetanus toxoid vaccination of adultsUnited States, 1993-1997. MMWR. 2000;49(SS09):39-62.
6. HurwitzES,HaberM,ChangA,etal. Effectiveness of influenza vaccination of day care children in reducing influenza-related morbidity among household contacts. JAMA. 2000;284: 1677-1682.