Influenza vaccination

Definition

An influenza vaccination is a vaccination that is used to protect persons against the viruses that cause influenza, which is also called the flu. Since the viruses that cause influenza are constantly changing, influenza vaccines are updated every year, and vaccination is recommended each year. It takes up to two weeks to develop protection after the shot, with the protection from the vaccination lasting up to one year.

Description

Every year in the United States about 36,000 people die from influenza-related complications, such as bacterial pneumonia, dehydration , or worsening of chronic medical conditions, such as congestive heart failure, asthma , or diabetes. Ninety percent of the deaths occur in persons 65 years and older. During influenza epidemics, hospitalization rates for older people increase two to five times compared to other seasons of the year. More than 200,000 people are hospitalized yearly with flu-related complications, and more than half of the hospitalizations are people 65 and older.

An influenza vaccination is the best way to be protected from contracting the flu. Older Hispanic and African-American adults are much less likely to be vaccinated against influenza than their white counterparts. The rate of vaccination of senior citizens as of 2005 was 65 percent in the U.S. African-Americans 65 years and older lag behind whites by about 21 percent in getting annual vaccinations , while Hispanic Americans 65 years and older lag behind whites by 19 percent. In large urban areas with high levels of unvaccinated persons, there is a potential for outbreaks of influenza; thus improving overall immunization coverage rates is essential. Studies have also shown that elderly people who choose to be vaccinated are generally in better health than those who fail to get the vaccine, so influenza control strategies should be developed to target those who are not being vaccinated. The United States Center for Disease Control (CDC) has set a target date of 2010 to increase influenza vaccinations to 90 percent among all adults aged 65 years and older, with an emphasis on vaccinating minority groups. In the U.S. the influenza vaccination is provided at no cost to all senior citizens covered by Medicare .

There are two types of influenza vaccines: the flu shot and the flu mist. The flu shot consists of inactivated (killed) influenza viruses and is given by injection into the muscle. With the flu mist, the live, attenuated (weakened) influenza vaccine (LAIV) is sprayed into the nostrils, but this type of vaccination is not recommended for persons over the age of 49. Each type of vaccine typically contains three influenza viruses, one A (H3N2) virus, one A (H1N1) virus, and one B virus. The strain of viruses included in the vaccine change yearly based on international surveillance data of influenza cases and estimations by scientists on what types and strains of viruses will be prevalent in the coming year. When the strains included in the vaccine are well-matched to the strains in the community, the vaccine usually can protect seven to nine out of ten vaccinated persons. However, in elderly people, the vaccine may not work as well in preventing influenza, but will result in decrease in severity of symptoms and in the risk of health complications.

Vaccinations against influenza are especially important for those who are not in good health. The vaccination is recommended for persons who have trouble swallowing or breathing, are receiving long term steroid therapy, or who have had heart attacks, heart disease , lung diseases such as asthma, emphysema , or chronic bronchitis , diabetes, HIV, blood disorders such as sickle cell anemia or other hemoglobinopathies, kidney or liver disease, or weakened immune systems. Persons with such conditions are at an increased risk of developing serious influenza-related complications. Persons who are at a high risk of complications and who have not received their influenza vaccination the preceding fall or winter should be vaccinated before travel to the tropics, travel with tourist groups, or travel to the Southern Hemisphere during April through September.

Recommended dosage

All persons 50 years of age and older should receive one dose intramuscularly of the inactivated influenza vaccine every year, ideally during the period from September to mid-November, but a vaccination received later may still be beneficial. Influenza can occur any time from November through May, with most cases usually occurring in January or February.

QUESTIONS TO ASK YOUR PHARMACIST

• What side effects should I worry about?

The influenza vaccine can be given with other vaccines, including the pneumococcal vaccine.

Precautions

Persons who should not be vaccinated against influenza without first contacting a physician for advice include:

• those who have a severe allergy to chicken eggs
• those who have had a severe reaction to an influenza vaccination previously
• those who previously developed Guillain-Barre Syndrome (a rare condition that results in weakness and paralysis of muscles of the body) within six weeks of getting an influenza vaccination
• In addition, a person who has a moderate or severe illness with a fever should wait to get vaccinated until their symptoms decrease.

Side effects

Although the risk of the influenza vaccine causing serious harm or death is small (and is much less than the health risks of contracting influenza), the vaccine, as with any medicine, can cause problems such as severe allergic reactions. Because the viruses in the vaccine have been killed, no one can get influenza from the vaccine. Mild problems that can occur soon after the vaccination is given and lasting 1 to 2 days include:

• soreness, redness, or swelling where the shot was given
• low grade fever
• aches
• chills
• general feelings of ill health

More severe problems that can be associated with the influenza vaccine are life-threatening allergic reactions, occurring within a few minutes to a few hours after the shot. A person should stay in the clinic where the shot was given for 15 minutes, in case an immediate reaction occurs. Such reactions could include hives, difficulty breathing, or swelling of the throat, tongue, or lips. If a severe reaction occurs after the person leaves the clinic, the emergency phone number should be called, or the person affected should be taken to an emergency facility as quickly as possible. The chance of such an adverse reaction occurring is estimated at less than one in a million people. Any adverse reaction should be reported to the U.S. Department of Heath and Human Services through the Vaccine Adverse Event Reporting Service. If a person has had a serious reaction to a vaccine, a federal program, the National Vaccine Injury Compensation Program, is available to help pay for the care of the person harmed or injured by the shot.

KEY TERMS

Guillain-Barre Syndrome —A disorder characterized by progressive symmetrical paralysis and loss of reflexes, usually beginning in the legs. The paralysis characteristically involves more than one limb (most commonly the legs), is progressive, and usually proceeds from the end of an extremity toward the torso. Guillain-Barre usually occurs after a respiratory infection, and it is apparently caused by a misdirected immune response that results in the direct destruction of the myelin sheath surrounding the peripheral nerves or of the axon of the nerve itself.

Influenza —Commonly known as flu; an infectious disease of birds and mammals caused by viruses of the family Orthomyxoviridae (the influenza viruses); common symptoms of the disease are the chills, then fever, sore throat, muscle pains, severe headache, coughing, weakness and general feelings of illness.

Vaccination —Injection of a killed or weakened microbe in order to stimulate the immune system against the microbe, thereby preventing disease. Vaccinations, or immunizations, work by stimulating the immune system, the natural disease-fighting system of the body. The healthy immune system is able to recognize invading bacteria and viruses and produce substances (antibodies) to destroy or disable them. Vaccinations prepare the immune system to ward off a disease. To immunize against viral diseases, the virus used in the vaccine has been weakened or killed.

In 1976, the swine flu vaccine was associated with persons developing the Guillain-Barre Syndrome. However, since that time, Guillain-Barre Syndrome had not been clearly linked to influenza vaccines.

Caregiver concerns

Care givers of the elderly should be vaccinated against influenza. Healthy care givers 49 years of age and younger may receive the LAIV vaccine, unless they are caring for persons with severely weakened immune systems who require a protected environment; these care givers should receive the inactivated vaccine. In addition, children, who are major spreaders of influenza in the community and introducers of influenza in households, should be vaccinated if they will be in contact with elderly persons.

ORGANIZATIONS

Center for Disease Control, http://www.cdc.gov/flu/.

Judith L. Sims