Table of Contents
Note: Amantadine is a standard treatment for Parkinson's disease and should be continued for that condition.
Viral Influenza Vaccines
"Flu Shots." These vaccines use inactivated (not live) viruses. They are designed to provoke the immune system to attack antigens found on the surface of the virus. (Antigens are foreign molecules that the immune system specifically recognizes as alien and targets for attack.)
Unfortunately, the antigens in these influenza viruses undergo genetic changes (called antigenic drift) over time, so they are likely to become resistant to a vaccine that worked in the previous year. Vaccines are then redesigned annually to match the current strain.
- Influenza A. The influenza A virus is further categorized by primary molecular antigens (hemagglutinin and neuraminidase), which serve as the targets for the vaccines. Influenza A is a particular problem, because it can infect other species, such as pigs or chicken, and undergo major genetic changes.
- Influenza B viruses tend to be more stable than influenza A viruses, but they too vary. Although influenza B has been far less common than A, a vaccine for type B is important because experts are concerned that small children will not have developed any immunity to the virus, and will experience severe flu if they are exposed to type B viruses.
Intranasal (inside the nose) vaccine. A live but weakened intranasal vaccine (FluMist) is proving to be effective and safe in healthy, non-pregnant people aged 2 - 49 years and has been approved by the FDA. It is known as a live, attenuated, intranasal influenza vaccine (LAIV). The vaccine is engineered to grow only in the cooler temperatures of the nasal passages, not in the warmer lungs and lower airways. It boosts the specific immune factors in the mucous membranes of the nose that fight off the actual viral infections. FluMist is given using a nasal spray. It should NOT be used in those who have asthma or in children under age 5 who have repeated wheezing episodes.
Timing and Effectiveness of the Vaccine. Ideally, everyone should be vaccinated every October or November. However, it may take longer for a full supply of the vaccine to reach certain locations. In such cases, the high-risk groups should be served first.
Antibodies to the flu virus usually develop within 2 weeks of vaccination, and immunity peaks within 4 - 6 weeks, then gradually wanes.
- Children younger than 9 years of age, who have not been previously vaccinated or received only 1 dose the previous year should be given 2 vaccine doses, spaced 4 weeks apart.
- It should be noted that if an individual develops flu symptoms and is accurately diagnosed in time, vaccination of the other members of the household within 36 - 48 hours affords effective protection to those individuals, according to a 2004 Canadian analysis of multiple studies.
In healthy adults, immunization typically reduces the chance of getting the seasonal flu by about 70 - 90%. The current flu vaccines may be slightly less effective in certain patients, such as the elderly and those with certain chronic diseases. Some evidence suggests, however, that even in people with a weaker response, the vaccine is usually protective against serious flu complications, particularly pneumonia. Some evidence suggests that among the elderly, a flu shot may help protect against stroke, adverse heart events, and death from all causes.
Everyone aged 6 months and over should get a flu vaccine; the only exception is for those who are allergic to the vaccine. It is especially important in the following groups, who are at a high risk for complications from the flu:
- People who are 50 or more years of age
- People who are 6 to 49 months of age
- People who have chronic lung disease, including asthma and COPD, or heart disease
- People who are 18 years old or younger AND taking long-term aspirin therapy
- People who have sickle cell anemia or other hemoglobin-related disorders
- People who have kidney disease, anemia, diabetes, or chronic liver disease
- People who have a weakened immune system (including those with cancer or HIV/AIDS)
- People who receive long-term treatment with steroids for any condition
- Women who are pregnant or plan to become pregnant during the flu season. Women who are pregnant should receive only the inactivated flu vaccine. (Vaccinations should usually be given after the first trimester. Exceptions may be women who are in their first trimester during flu season, because their risk from complications of the flu is higher than any theoretical risk to the baby from the vaccine)
Negative Effects
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Review Date: 01/29/2011
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine,
Harvard Medical School; Physician, Massachusetts General Hospital.
Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M.,
Inc.
A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)
