Medical Studies

Influenza Vaccination: Part I

According to Thompson, et al. (2003), approximately 51,000 people per year died annually due to influenza related diseases between 1990 and 1999. Mortality rates are appreciably higher for those over 65 years of age.

In order to reduce mortality and morbidity from influenza in the U.S., the CDC’s Advisory Committee on Immunization Practices (ACIP) released its “Prevention and Control of Influenza” guide this summer. The report documents important information regarding influenza and gives recommendations to patients and providers regarding when/for whom/in what manner influenza vaccinations should be administered.

According to this paper, influenza is divided into two types: influenza A and influenza B. Influenza A is further divided into two subgroups: hemagglutinin and neuraminidase. Influenza represents a unique family of viruses since antibodies developed against one strain of influenza offer little or no protection from other strains. There are also two types of vaccines. The live attenuated influenza vaccine (LAIV) uses live but weakened influenza virus. LAIV is administered through a nasal spray. The second, more traditional vaccine is the inactivated vaccine which is administered through an intramuscular injection and uses killed viruses. While the LAIV is often less unpleasant for the patient, it is usually more costly than the inactivated vaccine.

Hospitalization Rates
A variety of studies have found the following hospitalization rates which occur as a result of influenza. Below are a summary of a few studies which analyze the American population.

Years Population Age Hosp/100k – High Risk Hosp/100k – Healthy
’73-’93 TN Medicaid 0-11 mos 1900 496-1038
1-2 yrs 800 186
3-4 yrs 320 86
5-14 yrs 92 41
’92-’97 2 HMOs 0-23 mos 144-187
2-4 yrs 0-25
5-17 yrs 8-12
’68-’69 HMO 15-44 yrs 56-110 23-25
’70-’71 HMO 45-64 yrs 392-635 13-23
72-’73 HMO >64 yrs 399-518
’69-’95 Nat’l Hosp Data <65 yrs 20-42
’69-’95 Nat’l Hosp Data >64 yrs 125-228
’79-’01 Nat’l Hosp Data All 88

New Recommendations
The influenza vaccine is now recommended for a wide range of people (see “Persons for whom annual vaccination is recommended” below). Three important changes in ACIP’s vaccination policies for 2006 are:

  • Children under 6 years and parents of children under 6 should receive an annual flu vaccine.

  • Children under 9 years of age who have never been vaccinated should receive 2 doses of the vaccine.

  • Continued offering of the influenza vaccine even after influenza activity has been documented in a community.

Persons for whom annual vaccination is recommended

  • Children aged 6–59 months;

  • Women who will be pregnant during the influenza season;

  • Persons aged >50 years;

  • Children and adolescents (aged 6 months–18 years) who are receiving long-term aspirin therapy and, therefore, might be at risk for experiencing Reye syndrome after
    influenza infection;

  • Adults and children who have chronic disorders of the pulmonary or cardiovascular systems, including asthma (hypertension is not considered a high-risk condition);

  • Adults and children who have required regular medical follow-up or hospitalization during the preceding year because of chronic metabolic diseases (including diabetes
    mellitus), renal dysfunction, hemoglobinopathies, or immunodeficiency (including immunodeficiency caused by medications or by human immunodeficiency virus);

  • Adults and children who have any condition (e.g., cognitive dysfunction, spinal cord injuries, seizure disorders, or other neuromuscular disorders) that can compromise respiratory function or the handling of respiratory secretions, or that can increase the risk for aspiration;

  • Residents of nursing homes and other chronic-care facilities that house persons of any age who have chronic medical conditions;

  • Persons who live with or care for persons at high risk for influenza-related complications, including healthy household contacts and caregivers of children aged 0–59 months; and
  • Health-care workers.

The important changes