Flu Vaccination (cont.)
How effective is the flu vaccine?
The effectiveness of the flu vaccine is dependent upon
the extent of the match between the virus strains used to prepare the vaccine
and those viruses in actual circulation. The age and health status of the
individual also play a role in determining the effectiveness of the vaccine.
Research has shown that when there is a good match between the virus strains
chosen for the vaccine and those in circulation, the vaccine prevents influenza
illness in approximately 70%-90% of healthy adults under 65 years of age.
A study of children from 1-15
years of age showed that inactivated influenza vaccine was 77%-91% effective in
preventing influenza respiratory illness. The effectiveness of the vaccine in
preventing respiratory illness in people over 65 years of age is somewhat lower. Among older
people who reside in nursing homes, influenza vaccine is most effective in
preventing severe illness, secondary complications, and deaths. The vaccine can
be 50%-60% effective in preventing influenza-related hospitalization or
pneumonia and 80% effective in preventing influenza-related death, although the
effectiveness in preventing influenza respiratory illness can be as low as from
30%-40%.
What is the novel H1N1 ("swine" flu) vaccine, and who should receive it?
The H1N1 vaccine has been designed to provide immunity against the novel H1N1 flu, initially referred to as swine flu. It is important to note that this vaccine is different from the seasonal flu vaccine as described previously in this article. Both vaccines are necessary for optimal protection against the flu.
Two kinds of H1N1 flu vaccine are being produced, just as with the seasonal flu vaccine. An injection form (shot) that contains inactivated 2009 H1N1 virus is being produced as well as a 2009 H1N1 nasal spray flu vaccine that contains weakened (inactivated) virus. The same manufacturers who produce seasonal flu vaccines are producing 2009 H1N1 vaccines for use in the United States, and the vaccines are being made in the same way that the seasonal vaccines are made.
The H1N1 vaccine was scheduled to be available to the public in fall 2009, but delays caused the CDC to revise this estimate. In late October 2009, it was announced that vaccine doses would begin to be available within the coming few weeks.
Immunity to the 2009 H1N1 should occur about two weeks after the vaccination is given according to the CDC.
According to the CDC, guidelines for vaccination with the new H1N1 flu vaccine are as follows:
Certain groups of the population are recommended to receive the vaccine when it is first available according to the CDC's Advisory Committee on Immunization Practices (ACIP). These target groups include pregnant women, people who live with or care for children younger than 6 months of age, health-care and emergency medical services personnel, people between 6 months and 24 years
of age, and people between 25-64 years of age who are at higher risk for 2009 H1N1 flu because of chronic health disorders or compromised immune systems.
While a shortage of the H1N1 vaccine is not expected, in case the vaccine is available in limited quantities, the committee recommended that the following groups receive the vaccine before others: pregnant women, people who live with or care for children younger than 6 months of age, health-care and emergency medical services personnel with direct patient contact, children 6 months through 4 years of age, and children 5-18 years of age who have chronic medical conditions.
The committee further recommended that once the demand for vaccine for these target groups has been met at the local level, programs and providers should begin vaccinating everyone from 25-64 years
of age. Since studies indicate the risk for infection among people age 65 or older is less than the risk for younger age groups, as vaccine supply and demand for vaccine among younger age groups is being met, programs and providers should offer vaccination to people over the age of 65.
The U.S. Food and Drug Administration (FDA) has approved the use of one dose of 2009 H1N1 flu vaccine for people 10 years of age and older. For people under 10
years of age, the CDC recommends that two doses of 2009 H1N1 vaccine be given and separated by
four weeks. Infants younger than 6 months of age are too young to get the 2009 H1N1 and seasonal flu vaccines.
The 1976 swine flu virus and the 2009 H1N1 virus are different enough that it's unlikely a person who received the 1976 swine flu vaccine will have full protection from the 2009 H1N1. People vaccinated in 1976 against swine flu should still be given the 2009 H1N1 vaccine.
- There are two types of flu vaccines, the injection (with killed virus) and nasal spray vaccines (containing live, but weakened, virus).
- Each year, the influenza virus can change slightly, making the vaccine used in previous years ineffective.
- The vaccine is generally effective against the influenza virus within two weeks of administration.
- The vaccine is only effective against the strains of the virus that match the vaccine.
- The effectiveness of the flu vaccine is dependent upon the extent of the match between the virus strains used to prepare the vaccine and those viruses in actual circulation. The age and health status of the individual also play a role in determining the effectiveness of the vaccine.
REFERENCES:
The
information above was adapted in part from recommendations of the U.S. Centers
for Disease Control and Prevention (CDC), "Key Facts About Seasonal Influenza," 2009, and "Questions and Answers: 2009 H1N1 Influenza Vaccine," 2009.
Monto, A.S., Ohmit, S.E., Petrie, J.G., Johnson, E., Truscon, R., Teich, E., Rotthoff, J., Boulton, M., Victor, J.C. "Comparative efficacy of inactivated and live attenuated influenza vaccines." N Engl J Med 361.13 Sept. 24, 2009: 1260-7.
Rhorer, J., Ambrose, C.S., Dickinson, S., Hamilton, H., Oleka, N.A., Malinoski, F.J., Wittes, J. "Efficacy of live attenuated influenza vaccine in children: A meta-analysis of nine randomized clinical trials." Vaccine 27.7 Feb. 11, 2009: 1101-10.
Last Editorial Review: 11/2/2009
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