With this flu season, there are new indications for the traditional inactivated (killed) vaccine, a new intranasal vaccine, lab tests for rapid identification of influenza, and a need to review the role of antiviral treatments.
New prevention measures
Inactivated influenza vaccine is the best preventive measure against both type A and B strains of the virus. The vaccine’s effectiveness depends somewhat on how well it matches to circulating virus antigens. Table 1 lists the benefits of vaccination in various populations.
Table 2 identifies the usual target populations for vaccine coverage. In the past 5 years, research has yielded several findings: the very young are at excess risk of influenza-related hospitalizations; adults aged 50 to 64 years have more high-risk conditions than previously thought; and cost-benefit analyses show a large economic toll of flu outbreaks manifested mainly as work and school absence. Consequently, the Centers for Disease Control and Prevention (CDC) now recommends routine vaccination of persons older than 50 years, and encourages vaccination of children between 6 and 24 months.Children under 9 years being immunized for the first time must receive 2 vaccines at least a month apart to gain optimal protection. This requirement will make it challenging to immunize children aged <24 months, since they are already receiving a number of other vaccinations.
This year enough vaccine has been produced to allow both targeted and nontargeted groups to receive inactivated vaccine as soon as it is available.
TABLE 1
Effectiveness of inactivated influenza vaccine
| In the patient group… | …the vaccine prevents a potential… |
|---|---|
| Healthy adults <65 years | 70%–90% of influenza illness |
| Children 1–15 years | 77%–91% of influenza respiratory illness;no evidence that it prevents otitis media7 |
| Adults >65 years | 58% of influenza respiratory illness |
| 30%–70% of hospitalizations for pneumonia and flu | |
| Adults >65 years in nursing homes | 30%–40% of influenza illness |
| 50%–60% of hospitalizations | |
| 80% death rate |
TABLE 2
Persons who should receive inactivated influenza vaccine
| Recommendations to date |
|---|
|
| New recommendations |
|
FluMist
The US Food and Drug Administration (FDA) recently approved FluMist, an intranasal vaccine with live, attenuated influenza virus, effective against both type A and B strains. Indications for its use are healthy people from 5 to 49 years. In this group, FluMist is an alternative to the traditional inactivated vaccine, but it is more expensive at $46 a dose (compared with $6 to $10 for inactivated vaccine). Unvaccinated children 5 to 8 years of age should receive 2 doses 6 to 10 weeks apart.4
People with chronic conditions such as asthma, cardiovascular disease, diabetes, and known or suspected immunodeficiency should not receive this vaccine until additional data are acquired about its effectiveness in these situations. In addition, because FluMist contains live influenza viruses, there is a potential for transmission from the vaccinated person to other persons. Therefore, clinicians should be cautious in its use when a patient requiring vaccination lives with immunosuppressed persons.
The rate of serious side effects with FluMist has been <1%, although mild side effects such as runny nose, fever, and headache occur slightly more often among vaccine than placebo recipients.
Improved diagnostic tests
The development of new outpatient treatments for influenza has increased the desirability of making an accurate diagnosis. Clinical symptoms, particularly fever and cough, are somewhat helpful (in adults, sensitivity is 63%–78% and specificity is 55%–71%). Diagnostic accuracy is enhanced by awareness of active flu cases in your community. This information is available from local or state health departments and the CDC, and it is based on active surveillance through networks of sentinel physician practices and emergency rooms. This is a good example of a reliable surveillance system helping physicians provide better clinical care.
Progress to date
Since 1989, a concerted public health effort has increased flu vaccine usage in adults older than 65 from 33% to 66% in 1999.Like many successful population health programs, this improvement has resulted from a focus on the core functions of public health:
- Assessment—regular surveys of vaccine coverage and local influenza outbreaks, continual identification of high-risk groups, and studies of vaccine efficacy and cost-effectiveness.
- Assurance—media campaigns to heighten awareness among consumers and providers of the benefits of vaccination and increased access to vaccine through physician offices, health departments, other health care worksites, and non-traditional sites such as malls and drug stores.
- Policy development — Medicare coverage of vaccine costs since 1993, Healthy People 2000 and 2010 national goals, and marketing campaigns to increase vaccine coverage supported by the Public Health Service in partnership with private organizations.