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Influenza Immunization Two types of influenza
vaccine are now available: inactivated (or killed) vaccine and live attenuated
(or weakened) vaccine. The inactivated influenza vaccine is given as a
shot and has been used in the United States for many years. The attenuated
vaccine, licensed in 2003, is given as a nasal spray. It is approved for
healthy children and adults from 5-49 years of age. It is important to note that these types of vaccine are not interchangeable. Both the shot and the nasal spray are appropriate for distinct groups of children and adults. Influenza viruses can change in two different ways. One is called "antigenic drift." These are small changes in the virus that happen continually over time. Antigenic drift produces new virus strains that may not be recognized by the body's immune system. This process works as follows: a person infected with a particular flu virus strain develops antibody against that virus. As newer virus strains appear, the antibodies against the older strains do not recognize the "newer" virus well, and reinfection can occur. This is one reason why people can get the flu more than one time. In most years, one or two of the three virus strains in the influenza vaccine are updated to keep up with the changes in the circulating flu viruses. So, people who want to be protected from flu need to get a flu vaccine every year. Also, immunity wanes after a year! The other type of change is called "antigenic shift." Antigenic shift is an abrupt, major change in the influenza A viruses, resulting in new hemagglutinin and/or new hemagglutinin and neuraminidase proteins in influenza viruses that infect humans. Shift results in a new influenza A subtype. When shift happens, most people have little or no protection against the new virus. While influenza viruses are changing by antigenic drift all the time, antigenic shift happens only occasionally. Type A viruses undergo both kinds of changes; influenza type B viruses change only by the more gradual process of antigenic drift. To address the drift
and shift nature of the flu, the influenza vaccine is updated every year.
Protection develops about 2 weeks after getting the vaccine and may last
up to a year. Some people who get flu vaccine may still get the flu, but
they will usually get a much milder case than those who did not get the
vaccine. Flu vaccine should be given in October and may be given at the
same time as other vaccines, including pneumococcal vaccine. Some inactivated flu vaccine contains a trace amount of thimerosal, a form of mercury, as a preservative. There is no scientific evidence that thimerosal in vaccines is harmful, and the known benefits of the vaccine far outweigh any potential risk from thimerosal. If you have questions about thimerosal or reduced-thimerosal flu vaccine, ask your doctor. Side Effects from Influenza Immunization Serious complications
from inactivated flu vaccine are very rare. The viruses in inactivated
influenza vaccine have been killed, so you cannot get influenza from the
vaccine. Mild problems include soreness, redness, or swelling where the
shot was given; fever; and aches. If these problems occur, they usually
begin soon after the shot and last 1-2 days. Life-threatening allergic
reactions from vaccines are very rare. If they do occur it is within a
few minutes to a few hours after the shot. In 1976, swine flu
vaccine was associated with a severe paralytic illness called Guillain-Barre
Syndrome (GBS). Influenza vaccines since then have not been clearly linked
to GBS. However, if there is risk of GBS from current influenza vaccines,
it is estimated at 1 or 2 cases per million persons vaccinated - much
less than the risk of severe influenza, which can be prevented by vaccination. The chances of live
attenuated influenza vaccine viruses spreading from person to person are
very small. Even if such spread should occur, it is unlikely to cause
illness. Some children and adolescents 5-17 years of age have reported
mild reactions, including runny nose, nasal congestion or cough; fever;
headache and muscle aches; and abdominal pain or occasional vomiting or
diarrhea. Some adults 18-49 years of age have reported runny nose or nasal
congestion; cough, chills, tiredness/weakness; sore throat; and headache. Like any vaccine or
medicine, influenza vaccine could theoretically trigger a serious reaction
in someone who is allergic to one of its components. But severe allergic
reactions to childhood vaccines are fortunately very rare (estimated at
around one per million doses), and no child is ever known to have died
from an allergic reaction to a vaccine. Precautions Inactivated Influenza Vaccine should not be given to:
Live Intranasal Influenza Vaccine is indicated only for healthy persons between 5-49 years of age and should not be given to:
If you are severely
ill at the time the shot is scheduled, you should probably wait until
you recover before getting influenza vaccine. Talk to your doctor about
whether to reschedule this vaccination. After Getting Influenza
Vaccine . . . Content
derived from the Centers for Disease Control and Prevention, National
Center for Immunization and Respiratory Diseases |