Are You at Risk?
Some people are more likely to develop flu-related complications if they become sick from influenza.
Flu seasons are unpredictable. Although epidemics of flu happen every year, the timing, severity, and length depends on many factors, including what influenza viruses are spreading and whether they match the viruses in the vaccine. Flu viruses are constantly changing, so it’s not unusual for new strains to appear each year.
The timing of flu can vary from season to season. Flu activity most commonly peaks in the U.S. in January or February. However, seasonal flu activity can begin as early as October and continue as late as May.
Most people who get the flu have mild illness, do not need medical care or antiviral drugs, and recover in less than two weeks. Some individuals, however, are more likely to have flu complications that result in hospitalization and, occasionally, death.
The flu also can make chronic health problems worse. The following list includes the groups of people more likely to develop flu-related complications if they become sick from influenza:
(1) People who have medical conditions including:
- Neurological and neurodevelopmental conditions (including disorders of the brain, spinal cord, peripheral nerve, and muscle such as cerebral palsy, epilepsy, stroke, muscular dystrophy, or spinal-cord injury)
- Chronic lung disease
- Heart disease
- Blood disorders
- Endocrine disorders
- Kidney disorders
- Liver disorders
- Metabolic disorders
- Weakened immune system due to disease or medication
(2) Individuals younger than 19 who are receiving long-term aspirin therapy
(3) Those who are morbidly obese (Body Mass Index [BMI] of 40 or greater)
(4) Individuals at high risk for developing flu-related complications such as pneumonia, bronchitis, sinus infections, and
- Children younger than 5, especially those under age 2
- Adults 65 and older
- Pregnant women
- American Indians and Alaska natives
The Centers for Disease Control and Prevention (CDC) recommends a yearly flu vaccine for everyone 6 months of age and older as the first and most important step in protecting against this serious disease.
While many different flu viruses exist, the vaccine is designed to protect against the three main strains research indicates will cause the most illness during the flu season.
The United States Food and Drug Administration (FDA) chose the three influenza (flu) viruses for inclusion in the 2011–2012 seasonal flu vaccine based on recommendations
from the World Health Organization (WHO).
Each year, experts from FDA, WHO, CDC, and other institutions study virus samples collected from around the world to identify the influenza viruses most likely to cause illness during the upcoming flu season so people can be protected against them through vaccination.
The flu viruses selected for inclusion in the vaccines are updated each year based on information about which influenza viruses are being found, how they are spreading, and how well the previous season’s vaccine viruses might protect against any that are being newly identified.
Currently, 136 national influenza centers in 106 countries conduct year-round surveillance for influenza viruses and disease activity. These laboratories then send influenza viruses for additional analyses to the five WHO Collaborating Centers for Reference and Research on Influenza.
Three vaccine viruses are chosen to maximize the likelihood that the influenza vaccine will protect against the viruses most likely to spread and cause illness among people during the upcoming flu season.
WHO recommends specific vaccine viruses for production, but individual countries make their own decisions for licensing of vaccines. In the United States, FDA determines what viruses will be used in U.S.-licensed vaccines.
Getting the vaccine as soon as it becomes available each year is always a good idea, and the protection will last throughout the flu season.
It’s not possible to predict with certainty which flu viruses will predominate during a given season. Flu viruses are constantly changing. Called “drift,” they can change from one season to the next or even within the course of one flu season.
Experts must pick which ones to include in the vaccine many months in advance in order for it to be produced and delivered on time. Because of these factors, there is always the possibility of a less than optimal match between circulating viruses and those in the vaccine.
Antibodies made in response to vaccination with one strain of flu viruses can provide protection against different, but related, strains. A less than ideal match may result in reduced vaccine effectiveness against the variant viruses, but it can still provide some protection against influenza illness.
It’s important to remember that the flu vaccine contains three virus strains, so even when there is a less than ideal match or lower effectiveness against one strain, the vaccine may protect against the other two.
In addition to obtaining the vaccine, you can take everyday preventive steps like staying away from sick people and washing your hands to reduce the spread of germs. If you are sick with flu, stay home from work or school to prevent spreading influenza to others.
If you become sick, antiviral drugs can treat flu, making it milder and making you feel better faster. They also can prevent serious flu-related complications.
Are You at Risk?
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