 |
 |
English | Español
Información sobre vacunas
|
Actualizado por última vez: July 27, 2009 |
|
- Entendiendo la enfermedad
- Vacunas disponibles
- Historia de la vacuna
- Quienes deben y quienes no deben recibir esta vacuna
- Calendario de dosis
- Efectividad de la vacuna
- Efectos secundarios conocidos
- Asuntos relacionados
- Referencias clave y fuentes de información adicional
|
Entendiendo la enfermedad
Influenza viruses can affect anyone, but rates of infection are highest among children. Serious illnesses and death also occur in all age groups but rates are greatest in persons over the age of 65 years and those who have chronic health problems. Epidemics of influenza occur during the winter months nearly every year but the peak of influenza epidemics can occur as late as April or May and is not predictable from year to year. Influenza is spread through coughing and sneezing, and is highly contagious, especially in childcare centers, schools, and nursing homes.
Uncomplicated influenza generally comes on suddenly, and symptoms include muscle aches, fever, chills, headache, cough, and runny nose; it lasts for 3-7 days although cough can persist for about 2 weeks. The respiratory illnesses caused by influenza viruses are clinically difficult to distinguish from the illnesses caused by other respiratory infections. Young infants may have symptoms that mimic invasive bacterial infections with high fevers and fussiness, leading to hospitalization. Although most young children who are hospitalized with influenza virus infections are only in the hospital for a few days, some require treatment in an intensive care unit. The majority of children who are hospitalized for influenza infection are less than 5 years of age and a quarter of them are less than 6 months old.
Influenza viruses can cause viral pneumonia, can make underlying medical conditions worse, and can lead to bacterial pneumonia, sinusitis and ear infections. Influenza virus infections have also been associated with inflammation of the heart and, brain swelling with liver failure. On average, influenza virus infections cause approximately 36,000 deaths and 148,000 hospitalizations each year in the United States.
More than 90% of influenza-related deaths are in people aged 65 years or older. Although influenza-related deaths are much less common in children than the elderly, fatal cases have been increasingly recognized. |
Vacunas disponibles
Product: Afluria®
Manufacturer: CS Limited
Year Licensed: 2007
Product: FluLaval®
Manufacturer: ID Biomedical Corporation of Quebec
Year Licensed: 2006
Product: FluMist®
Manufacturer: MedImmune Vaccines
Year Licensed: 2003
Product: Fluvirin®
Manufacturer: Chiron Corporation
Year Licensed: 1988
Product: Fluzone®
Manufacturer: Aventis Pasteur
Year Licensed: 1978
FluMist® does not contain thimerosal. Both Fluvirin® and Fluzone® are available with reduced thimerosal formulation. For information on the thimerosal content in these vaccines, see the Food and Drug Administration at www.fda.gov/cber/vaccine/thimerosal.htm#t3 or Johns Hopkins University's Institute for Vaccine Safety at
www.vaccinesafety.edu/thi-table.htm |
Historia de la vacuna
Influenza vaccines have been used since 1945. Each year, the vaccines contain three virus strains that are expected to affect the United States in the upcoming winter.
Until recently, all available influenza vaccines were trivalent inactivated (killed) influenza virus vaccines (TIV). Inactivated influenza virus vaccines cannot cause influenza. TIV came in whole-virus and split-virus forms prior to 2001; however, because of fewer side effects, including fever and reactions at the injection site, only split-virus TIVs are currently available in the U.S.
In June of 2003, a live, attenuated, cold adapted, temperature sensitive, trivalent influenza virus vaccine (LAIV) was licensed in the United States. The temperature sensitive type A and B strains of influenza virus contained in LAIV replicate (multiply) in the nasal passages but not in the lower respiratory tract.
Due to the change in the types of influenza viruses circulating each year, some of the virus components of the influenza vaccines must be changed as well. |
Quienes deben y quienes no deben recibir esta vacuna
Who should receive the TIV each year?
All children more than 6 months of age, all adults over 50 years of age, and all persons who work in the healthcare industry should be immunized annually. In addition, people at increased risk of developing complications from influenza should be immunized, including those who:
- Are women who will be pregnant during the influenza season (November to April).
- Influenza vaccine is recommended for all contacts of children less than 5 years of age, including women who are breastfeeding. Women who are breastfeeding may receive either TIV or LAIV (unless LAIV is contraindicated because of other medical conditions).
- People who can transmit influenza viruses to those at high risk for complications, including:
- Members of households with high-risk persons, including households that will include children younger than 6 months, persons coming in contact with children less than 6 months of age, and persons who will come into contact with persons who live in nursing homes or other long-term care facilities.
- Have long-term disorders of the lungs, heart, or circulation (including asthma or cystic fibrosis).
- Have metabolic diseases (including diabetes).
- Have kidney disorders.
- Have blood disorders (including anemia or sickle cell disease).
- Have weakened immune systems (including immunosuppression caused by medications, malignancies, organ transplant, or HIV infection).
- Are children who receive long-term aspirin therapy (and therefore have a higher chance of developing Reye syndrome if infected with influenza).
In addition, influenza vaccine is encouraged for healthy people six months of age or older, who:
- Plan to travel to foreign countries and areas where flu outbreaks may be occurring, such as the Tropics and the Southern Hemisphere from April through September.
- Travel as a part of large organized tourist groups that may include persons from areas of the world where influenza viruses are circulating.
- Attend school or college and reside in dormitories, or reside in institutional settings.
- Wish to reduce their risk of becoming ill with influenza
Who should not receive influenza vaccine:
- Infants younger than six months of age.
- People who have had an anaphylactic reaction (allergic reactions that cause difficulty breathing, which is often followed by shock) to eggs, egg products, or other components of the flu vaccine. There are antiviral agents which doctors can prescribe as an alternative for preventing influenza in such people.
- Children younger than four years of age should not receive Fluvirin®1 (Chiron Corp.) because it has not been proven effective for them.
- Children younger than two years of age and adults over 49 years of age should not receive LAIV because safe use in these age groups has not been established.
- LAIV should not be given to children and adolescents (2-17 years of age) receiving aspirin or aspirin-containing medications, because of the complications associated with aspirin and wild-type influenza virus infections in this age group.
- People with a history of asthma or other reactive airway diseases should not be given LAIV.
- People with chronic underlying medical conditions that may predispose them to severe influenza infections should also not be given LAIV. For these people, TIV is indicated.
- LAIV should not be given to pregnant women.
- LAIV should not be given to people with a history of Guillain-Barre syndrome.
- LAIV should not be given concurrently with other live-virus vaccines.
- People with acute serious illness with fever
- People who are moderately or severely ill should consult with their physician before receiving any vaccine
- Under no circumstances should LAIV be given by injection.
Influenza immunization is recommended by:
- Advisory Committee on Immunization Practices of the Centers for Disease Control and Prevention
- American Academy of Family Physicians
- American Academy of Pediatrics
- American Thoracic Society
The summary of adolescent/adult immunization recommendations can be found at: www.cdc.gov/nip/recs/adult-schedule.pdf
1 NNii uses vaccine trade names only for clarity in our presentation of immunization recommendations. NNii does not recommend specific vaccine brands over others.
|
Calendario de dosis
TIV is given by the intramuscular route; LAIV is administered as a nasal spray. The formulation of influenza vaccines differ according to the manufacturer. TIV formulations in multidose vials contain thimerosal as a preservative.
When young children (six months until nine years old) are vaccinated against influenza for the first time, they should receive two doses of age-appropriate influenza vaccine given one month apart. Those children who received only one dose in their first year of vaccination should receive two doses in the following year. Two doses administered 4 weeks apart are also recommended for children 2 -8 years of age who are receiving LAIV for the first time. For children 6-35 months of age, a half dose (0.25 ml) of TIV (injected) is recommended, in contrast to 0.5 ml which is the usual dose for everyone over three years of age.
In the United States, Fluzone® (Aventis Pasteur) may be administered to children as young as six months of age. Fluvirin® (Novartis Corp.) should only be given to children four years of age and older because its efficacy in younger people has not been demonstrated. Fluarix®, Flulaval®, and Afluria® are not licensed for use in children but is licensed for adults 18 years of age and older. LAIV should only be given to healthy children and adolescents, ages 2-17 years, and healthy adults, ages 18-49.
People nine years of age or older should receive one dose of influenza vaccine each year. Ideally, people should receive their influenza vaccine from the beginning of October through November each year, prior to the influenza season, which generally peaks during late December through early March. However, vaccination later in the season is considered worthwhile.
|
Efectividad de la vacuna
Each year, the influenza vaccine contains three virus strains, representing the influenza viruses thought to be the most likely to circulate in the United States in the upcoming winter.
When the match between the virus strains in the vaccine and the circulating viruses is close, the vaccine prevents illness in up to 90% of healthy adults under the age of 65. Among elderly people, the vaccine is about 30-70% effective in preventing disease, but it is 50-60% effective in preventing hospitalization and 80% effective in preventing influenza-related death in the elderly.
The vaccine protects between 45% and 90% of healthy children from getting influenza. Studies indicate that the older and healthier children who have received the influenza vaccine are, the more likely they will be protected. Influenza vaccination has also been shown to decrease middle ear infections among young children by about 30%.
One goal for widespread influenza vaccine utilization in the United States is to decrease the transmission of influenza viruses. Epidemiologic studies have demonstrated that children have the highest rates of influenza virus infections, suggesting that universal immunization of children could result in transmission of these viruses within communities, from persons providing care or who are household contacts of people who are high risk for complications from influenza (including young infants less than 6 months of age (for whom there is no effective vaccine and no licensed treatment)), those with chronic diseases and those who are older than 50 years of age (especially those who are over 65 years of age).
Of particular concern are healthcare workers who also commonly acquire influenza virus infections and who have transmitted influenza viruses in hospitals and long-term care facilities. Vaccination of healthcare workers has been associated with decreased deaths among nursing homes, for example.
|
Efectos secundarios conocidos
The majority of those immunized with TIV will have no adverse reactions. Of those who do have a side effect, most will have soreness or tenderness at the injection site. Fewer than 1% of adults immunized will also experience fever, chills, or a general sense of feeling unwell that lasts one to two days. Children are more likely to experience these symptoms.
In very rare cases (far less than 1 out of 10,000), serious reactions can occur. People who have an allergy to eggs (which are used in making the vaccine) or any component of the vaccine are at greater risk for a serious allergic reaction. If you or your child has developed hives or swollen lips or tongue; has had trouble breathing; or has collapsed after eating eggs or receiving a previous dose of influenza vaccine, consult with your healthcare provider to see if the vaccine should be given.
Because of a slight increase in the frequency of Guillain-Barre Syndrome [GBS] (a progressive disorder affecting the nervous system) associated with the 1976 swine flu vaccine, subsequent flu vaccines have been closely monitored. It has been estimated that about one case of GBS may occur per million persons immunized with TIV, although these cases may not be related to TIV. If a person is not at high risk for getting complications from influenza, a person who developed GBS within six weeks of a previous influenza shot should avoid subsequent influenza shots. If the risk from influenza is high, they should be vaccinated with an age-appropriate inactivated influenza vaccine because the established benefits of the vaccine justify vaccination. LAIV should not be given to individuals who have a history of GBS because safety in those persons has not been investigated.
|
Asuntos relacionados
Influenza vaccines given as a nasal spray are being used for adults in Russia, and have been under development in the U.S. since the 1960's. LAIV administered as a nasal spray was approved by the FDA in June of 2003. It is the first nasally administered vaccine to be marketed in the United States and the first live virus influenza vaccine approved in the U.S. The possible advantages of this type of vaccine are that it is easy to administer, has the potential to induce a broad mucosal and systemic immune response, and has been shown to be approximately 87% effective in children. Although TIV and LAIV appear to have similar effectiveness and safety profiles, no study has directly compared the efficacy or effectiveness of TIV and trivalent LAIV.
When there is a major change in the influenza virus strain from one year to the next, epidemics or pandemics (world outbreaks) can occur. During the 20th century, there were four major pandemics; the worst caused 21 million deaths worldwide and 500,000 deaths in the U.S. from 1918 to 1919. Between 1957 and 1986 there were 19 different flu epidemics in the U.S.; several of the most recent caused more than 40,000 deaths.
|
Referencias clave y fuentes de información adicional
|
Vea también nuestra galería de imágenes de enfermedades.
|
|
|
|
|
