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Influenza and Influenza Vaccine

Influenza and Influenza Vaccine. Epidemiology and Prevention of Vaccine-Preventable Diseases National Center for Immunization and Respiratory Diseases Centers for Disease Control and Prevention. Revised May 2009. Influenza Antigenic Changes. Antigenic Shift major change, new subtype

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Influenza and Influenza Vaccine

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  1. Influenza and Influenza Vaccine Epidemiology and Prevention of Vaccine-Preventable Diseases National Center for Immunization and Respiratory Diseases Centers for Disease Control and Prevention Revised May 2009

  2. Influenza Antigenic Changes • Antigenic Shift • major change, new subtype • caused by exchange of gene segments • may result in pandemic • Example of antigenic shift • H2N2 virus circulated in 1957-1967 • H3N2 virus appeared in 1968 and completely replaced H2N2 virus

  3. Influenza Antigenic Changes • Antigenic Drift • minor change, same subtype • caused by point mutations in gene • may result in epidemic • Example of antigenic drift • in 2002-2003, A/Panama/2007/99 (H3N2) virus was dominant • A/Fujian/411/2002 (H3N2) appeared in late 2003 and caused widespread illness in 2003-2004

  4. Influenza Clinical Features • Incubation period 2 days (range 1-4 days) • Abrupt onset of fever, myalgia, sore throat, nonproductive cough, headache • Severity of illness depends on prior experience with related variants

  5. Influenza Complications • Pneumonia • secondary bacterial • primary influenza viral • Reye syndrome • Myocarditis • Death 0.5-1 per 1,000 cases

  6. Impact of Influenza-United States, 1990-1999 • Approximately 36,000 influenza-associated deaths during each influenza season • Persons 65 years of age and older account for more than 90% of deaths • Higher mortality during seasons when influenza type A (H3N2) viruses predominate

  7. Impact of Influenza-United States, 1990-1999 • Highest rates of complications and hospitalization among young children and person 65 years and older • Average of more than 200,000 influenza-related excess hospitalizations • 57% of hospitalizations among persons younger than 65 years of age • Greater number of hospitalizations during type A (H3N2) epidemics

  8. Influenza Among School-Aged Children • School-aged children • typically have the highest attack rates during community outbreaks of influenza • serve as a major source of transmission of influenza within communities

  9. Month of Peak Influenza Activity United States, 1976-2008 47% 19% 13% 13% 3% 3% MMWR 2006;55:22

  10. Influenza Vaccines • Inactivated subunit (TIV) • intramuscular • trivalent • split virus and subunit types • duration of immunity 1 year or less • Live attenuated vaccine (LAIV) • intranasal • trivalent • duration of immunity at least 1 year

  11. Inactivated Influenza Vaccine Efficacy • 70%-90% effective among healthy persons younger than 65 years of age • 30%-40% effective among frail elderly persons • 50%-60% effective in preventing hospitalization • 80% effective in preventing death

  12. Vaccinated* Unvaccinated Influenza and Complications Among Nursing Home Residents RR=1.9 RR=2.0 RR=2.5 RR=4.2 *Inactivated influenza vaccine. Genesee County, MI, 1982-1983

  13. LAIV Efficacy in Healthy Children • 87% effective against culture-confirmed influenza in children 5-7 years old • 27% reduction in febrile otitis media (OM) • 28% reduction in OM with accompanying antibiotic use • Decreased fever and OM in vaccine recipients who developed influenza

  14. LAIV Efficacy in Healthy Adults • 20% fewer severe febrile illness episodes • 24% fewer febrile upper respiratory illness episodes • 27% fewer lost work days due to febrile upper respiratory illness • 18%-37% fewer days of healthcare provider visits due to febrile illness • 41%-45% fewer days of antibiotic use

  15. Timing of Influenza Vaccine Programs • Influenza activity can occur as early as October • In more than 80% of seasons since 1976, peak influenza activity has not occurred until January or later • In more than 60% of seasons the peak was in February or later

  16. Timing of Influenza Vaccine Programs • Providers should begin offering vaccine soon after it becomes available, if possible by October • To avoid missed opportunities for vaccination, providers should offer vaccine during routine healthcare visits or during hospitalizations whenever vaccine is available

  17. Dose 0.25 mL 0.50 mL 0.50 mL Age Group 6-35 mos 3-8 yrs >9 yrs No. Doses 1* or 2 1* or 2 1 Inactivated Influenza Vaccine Schedule *Only one dose is needed if the child received 2 doses of influenza vaccine during the previous influenza season

  18. Influenza Vaccination of Children • Children 6 months through 8 years of age who did not receive the recommended second dose of influenza vaccine in the initial year that they received influenza vaccine should receive 2 doses during the next influenza season* • Children 6 months through 8 years of age who are being vaccinated two or more seasons after receiving an influenza vaccine for the first time should receive a single annual dose, regardless of the number of doses administered previously *applies only to the influenza season that follows the first season that a child younger than 9 years receives influenza vaccine

  19. Influenza Vaccination Schedule • All children younger than 9 years receiving seasonal influenza vaccine for the first time this season should receive 2 doses, separated by 4 weeks • Children younger than 9 years who received a seasonal vaccine for the first time last season but who received only 1 dose should receive 2 doses this season MMWR 2010;59 (early release) From the Immunization Update 2010 webcast (originally broadcast August 5, 2010

  20. Influenza Vaccination Schedule • Children younger than 9 years who did not receive at least 1 dose of a 2009 monovalent vaccine should receive 2 doses of seasonal vaccine this season • Children younger than 9 years whose 2009 pandemic vaccine history is not known should receive 2 doses this season MMWR 2010;59 (early release) From the Immunization Update 2010 webcast (originally broadcast August 5, 2010

  21. Live Attenuated Influenza VaccineIndications • Healthy*, nonpregnant persons 2 through 49 years of age, including • healthy children • healthcare personnel • persons in close contact with high-risk groups • persons who want to reduce their risk of influenza *Persons who do not have medical conditions that increase their risk for complications of influenza

  22. Fluzone High-Dose TIV • Approved only for persons 65 years of age or older • Each dose contains 4 times as much hemagglutinin as the regular formulation of Fluzone for adults • ACIP has not expressed a preference for the high dose Fluzone formulation or any other inactivated vaccine for use in persons 65 years and older MMWR 2010;59 (early release) From the Immunization Update 2010 webcast (originally broadcast August 5, 2010

  23. Inactivated Influenza Vaccine Adverse Reactions Local reactions 15%-20% Fever, malaise not common Allergic reactions rare Neurological very rare reactions

  24. Live Attenuated Influenza VaccineAdverse Reactions • Children • no significant increase in URI symptoms, fever, or other systemic symptoms • significantly increased risk of asthma or reactive airways disease in children 12-59 months of age • Adults • significantly increased rate of cough, runny nose, nasal congestion, sore throat, and chills reported among vaccine recipients • no increase in the occurrence of fever • No serious adverse reactions identified

  25. Inactivated Influenza VaccineContraindications and Precautions • Severe allergic reaction to a vaccine component (e.g., egg) or following a prior dose of vaccine • Moderate or severe acute illness • History of Guillian Barré syndrome within 6 weeks following a previous dose of TIV (precaution)

  26. Live Attenuated Influenza VaccineContraindications and Precautions • Children younger than 2 years of age* • Persons 50 years of age or older* • Persons with chronic medical conditions* • Children and adolescents receiving long-term aspirin therapy* *These persons should receive inactivated influenza vaccine

  27. Live Attenuated Influenza VaccineContraindications and Precautions • Immunosuppression from any cause* • Pregnant women* • Severe (anaphylactic) allergy to egg or other vaccine components • History of Guillian-Barré syndrome • Children younger than 5 years with recurrent wheezing* • Moderate or severe acute illness *These persons should receive inactivated influenza vaccine

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