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  • Children between the ages of 6 months and 8 years who are receiving the influenza vaccination for the first time require a booster vaccination at least 4 weeks after their initial influenza vaccination.
  • Because of the novelty of the 2009(H1N1) influenza virus, which is again expected to circulate in 2012-2013 and is included in the current trivalent vaccine, only children who received 2 or more doses of influenza vaccine since July 1, 2010, should receive 1 dose this year. This ensures that children who have previously only had 1 exposure to the H1N1 antigen receive a booster.
  • New intradermal preparations of the influenza vaccine include a dose of 9 µg of hemagglutinin per vaccine virus strain with an indication for adults 18 to 64 years old, and a high-dose vaccine featuring 60 µg of hemagglutinin per vaccine virus strain for patients 65 years and older.
  • The ACIP does not recommend one form of TIV vaccine vs another.
  • The intranasally administered live-attenuated influenza vaccine is indicated for healthy, nonpregnant persons between the 2 and 49 years old. There is generally no preference for live vs inactivated vaccines among this age group, although persons with a history of egg allergy should receive the inactivated vaccine.
  • Febrile seizures have an overall prevalence of 2% to 5% among children. The 2010-2011 influenza season was remarkable for the first time in that the influenza vaccine was associated with a higher risk for febrile seizures. This risk was limited to children between the ages of 6 months and 4 years, and it occurred during the 24 hours after receipt of the vaccine. Concomitant administration of the PVC13 vaccine increased the risk for febrile seizure associated with the influenza vaccine.
  • Reports of a higher risk for febrile seizures associated with the vaccine Afluria have led the CDC to recommend against the use of this specific product among children younger than 9 years.
  • Among persons with a history of egg allergy, those who report only hives after exposure to eggs may receive TIV, provided that the healthcare practice is familiar with the potential manifestations of egg allergy and can monitor the patient for at least 30 minutes after administration of the vaccine.
  • Measures such as splitting the vaccine into 2 separate injections or skin testing with the vaccine are unnecessary among patients with egg allergy.
  • If clinicians wish to administer the influenza vaccine to patients with more severe symptoms of egg allergy (ie, anaphylaxis), they should refer these patients to an allergy specialist for consultation.
  • Predicting the predominant circulating strain of influenza B in a given year is a challenge. Therefore, several quadrivalent influenza vaccines are being developed, including a live attenuated vaccine.

 

CLINICAL IMPLICATIONS

 

  • The influenza vaccine is recommended for all individuals 6 months and older. Children who received 2 or more doses of influenza vaccine since July 1, 2010, should receive 1 dose this year. Otherwise, children younger than 8 years should receive a booster vaccination at least 1 month after primary vaccination.
  • Persons who report only hives after exposure to eggs may receive TIV, provided that the healthcare practice is familiar with the potential manifestations of egg allergy and can monitor the patient for at least 30 minutes after administration of the vaccine.

Fonte: Medscape Pharmacist

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Pedro Plans. Recommendations for the Prevention and Treatment of Influenza Using Antiviral Drugs Based on Cost–Effectiveness. Expert Review of Pharmacoeconomics & Outcomes Research. Mar. 2009

 nfluenza A virus can produce sudden and unpredictable pandemics. Influenza A viruses are classified into different subtypes based on their surface glycoproteins, hemagglutinin (H) and neuraminidase (N). A total of 15 subtypes of hemagglutinin (i.e., H1–H15) and nine subtypes of neuraminidase (i.e., N1–N9) have been identified. All of these serotypes have been found in aquatic birds. Different species of wild birds form the primary natural reservoir of the influenza A virus. In humans, however, only three hemagglutinin proteins (i.e., H1, H2 and H3) and two neuraminidase proteins (i.e., N1 and N2) have been detected in epidemics and pandemics since 1900.

Since the discovery of the influenza virus, new antigenic variants of influenza A and B have continually emerged. The influenza virus changes continually by means of two mechanisms, called antigenic drift and antigenic shift.The antigenic shift is responsible for the major antigenic changes registered in human influenza A virus. The antigenic shift is produced by the reassortment of genetic components from human and nonhuman influenza viruses. The antigenic shift produces new human influenza viruses with antigenic components from the nonhuman viruses. For example, the genetic reassortment of the human influenza virus H2N1 and the avian influenza viruses H5N8 and H3N4 can produce new human influenza viruses H5N1 and H3N1, respectively. Influenza pandemics are produced by the lack of a specific immune response against the new human virus in the whole population of the world. People infected by one influenza virus develop a specific immune response against the HN strain that is unable to recognize the new viral strain.

Antiviral drugs can be used to treat influenza cases and block the spread of a new influenza pandemic in the population. The WHO recommends neuraminidase inhibitors for patients with H5N1 influenza and their contacts because oseltamivir is active against H5N1 influenza and there are no alternative treatments.Recent avian influenza outbreaks of H5N1 strains, however, were not transmitted from human to human.

Many countries are stockpiling antiviral drugs (oseltamivir) in preparation for a possible influenza pandemic. Siddiqui and Edmunds assessed the cost–effectiveness of antiviral stockpiling for the prevention and treatment of pandemic influenza in the UK.The cost–effectiveness was assessed on the assumptions of a stockpile of 14.6 million units, an attack rate of clinical influenza of 25%, mortality rates similar to those registered in 1957 and/or 1969 or the 1918 pandemics and a time-to-pandemic of 30 years. The cost–effectiveness of treating all symptomatic individuals was £1900 or £13,000 per QALY depending on the mortality. The cost–effectiveness of using a test-treatment strategy, where only laboratory-confirmed cases were treated, was associated with a cost–effectiveness ratio of £31,000 or £228,000 per QALY, depending on the mortality considered. These results demonstrate that the stockpiling of antiviral drugs for the treatment of all symptomatic patients is a cost-effective intervention.

Influenza vaccines and antiviral drugs for influenza are essential components of a comprehensive pandemic response. During a pandemic, antivirals could reduce morbidity and mortality from influenza and block transmission of influenza virus in the population. Given that the vaccine is unlikely to be available during the early months of the pandemic, antivirals will be the only intervention during the initial response. The priority groups for antiviral treatment are people at risk and people living with or caring for high-risk individuals; however, antivirals can be given to other people depending on the stockpile of antivirals.

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