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Influenza and Influenza Vaccines

Influenza and Influenza Vaccines. K. Vahdat 25/11/1391. Influenza. Highly infectious viral illness Epidemics reported since 16 th century. Influenza Virus Strains. Type A moderate to severe illness all age groups humans and other animals Type B changes less rapidly than type A

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Influenza and Influenza Vaccines

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  1. Influenza and Influenza Vaccines K. Vahdat 25/11/1391

  2. Influenza • Highly infectious viral illness • Epidemics reported since 16th century

  3. Influenza Virus Strains • Type A • moderate to severe illness • all age groups • humans and other animals • Type B • changes less rapidly than type A • milder epidemics • humans only • primarily affects children

  4. H N Influenza Type A Subtypes • Subtypes of type A determined by hemagglutinin (H) and neuraminidase (N)

  5. Surface Antigens and Immunity • Immunity reduces likelihood of infection and severity of disease. • Antibodies are specific to different types of surface antigens. • Changes in H and N allow virus to evade previously developed immune responses. • Antigenic changes: drift and shift.

  6. Influenza Antigenic Changes • Antigenic Drift • Minor change, same subtype • Caused by point mutations in gene • May result in epidemic • Example of antigenic drift • In 2003-2004, A/Fujian/411/2002-like (H3N2) virus was dominant • A/California/7/2004 (H3N2) began to circulate and became the dominant virus in 2005

  7. 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

  8. Burden of Influenza • 10% to 20% of the population is infected with influenza virus each year. • Average of more than 200,000 excess hospitalizations each year. • Persons 65 and older and 2 years and younger at highest risk • Average of 36,000 deaths each year. • Persons 65 and older at highest risk of death

  9. Influenza Vaccines • Inactivated subunit (TIV) • Intramuscular • Trivalent • Annual • Live attenuated vaccine (LAIV) • Intranasal • Trivalent • Annual

  10. influenza vaccines for 2012–13 contain: • A/California/7/2009 (H1N1)-like, A/Victoria/361/2011 (H3N2)-like, B/Wisconsin/1/2010-like (Yamagata lineage) antigens. • Children aged 6 months through 8 years require 2 doses of influenza vaccine (administered a minimum of 4 weeks apart) during their first season of vaccination to optimize immune response.

  11. Inactivated Influenza Vaccines *inactivated vaccines approved for children younger than 4 years

  12. Why a Yearly Influenza Vaccination • Influenza vaccine expires June 30 (10 Tir) each year. • Antibodies wane during the year. • Surface antigens drift and shift.

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

  14. Inactivated Influenza Vaccine Adverse Reactions • Local reactions 15% - 20% • Fever, malaise uncommon • Allergic reactions rare • Neurological very rare reactions

  15. Inactivated Influenza Vaccine Adverse Reactions • Inactivated influenza vaccine contains only noninfectious fragments of influenza virus • Inactivated influenza vaccine cannot cause influenza disease

  16. TIV Schedule Dose 0.25 mL 0.50 mL 0.50 mL No. Doses 1 or 2 (4 week interval) 1 or 2 (4 week interval) 1 Age Group 6-35 mos 3-8 yrs 9 yrs and older

  17. LAIV Efficacy • Against lab-confirmed influenza following experimental challenge • LAIV 85% effective • TIV 71% effective • No significant difference

  18. Live Attenuated Influenza Vaccine Adverse Reactions • Children • No significant increase in URI symptoms, fever, or other systemic symptoms • Increased risk of asthma or reactive airways disease in children 12-59 months of age • Adults • 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

  19. LAIV Indications • Healthy* persons 5 – 49 years of age • Close contacts of persons at high risk for complications of influenza (except severely immunosuppressed) • Persons who wish to reduce their own risk of influenza • Healthcare workers *Persons who do not have medical conditions that increase their risk for complications of influenza

  20. LAIV Schedule Age Group 6 mos – 8 years 9 yrs and older Dose 0.2 mL 0.2 mL No. Doses 1 or 2 (4 week interval) 1

  21. Transmission of LAIV Virus LAIV replicates in the NP mucosa Mean shedding of virus 7.6 days – longer in children One instance of transmission of vaccine virus documented in a day care setting Transmitted virus retained attenuated, cold adapted, temperature sensitive characteristics Transmitted attenuated vaccine virus unlikely to cause typical influenza symptoms

  22. Use of LAIV Among Healthcare Personnel No instances of transmission of LAIV have been reported in the U.S. ACIP recommends that LAIV can be given to eligible HCWs except those that care for severely immuno-suppressed persons (hospitalized and in isolation) No special precautions are required for HCWs who receive LAIV

  23. LAIV Storage Must be stored at 35 - 46 degrees Fahrenheit Similar to TIV If inadvertently frozen, return to refrigerator

  24. TIV preparations, with the exception of Fluzone Intradermal (Sanofi Pasteur), should be administered intramuscularly. • Fluzone Intradermal is indicated for persons aged 18 through 64 years • The intranasally administered live-attenuated influenza vaccine (LAIV), FluMist (MedImmune), is indicated for healthy, nonpregnant persons aged 2 through 49 years

  25. No preference is indicated for LAIV versus TIV in this age group • Persons with a history of egg allergy should receive TIV rather than LAIV.

  26. Influenza Season • Recommended Groups for Vaccination • Children 6-59 months of age • Healthy adults 50 years old and older • Persons 5 – 49 years old at high risk for complications • Pregnant women • Residents of nursing homes • Household contacts of persons at high risk for complications • Health care workers

  27. Influenza: High Risk for Complications • Birth through 59 months of age • Adults 50 years old and older • Chronic lung disease, asthma • Chronic heart disease • Metabolic diseases, e.g. diabetes • Chronic renal disease • High risk of aspiration • Immunosuppression • Pregnancy • Chronic aspirin therapy: 18 years old and younger

  28. HIV Infection and Inactivated Influenza Vaccine • Persons with HIV at higher risk for complications of influenza • TIV induces protective antibody titers in many HIV-infected persons • Transient increase in HIV replication reported • TIV will benefit many HIV-infected persons

  29. Pregnancy and Inactivated Influenza Vaccine • Risk of hospitalization 4 times higher than nonpregnant women • Risk of complications comparable to nonpregnant women with high risk medical conditions • Vaccination (with TIV) recommended for all women who will be pregnant during the influenza season, regardless of gestational age

  30. Influenza Vaccine Recommendations • Immunization providers should administer influenza vaccine to any person who wishes to reduce the likelihood of becoming ill with influenza or transmitting influenza to others *Healthy persons 5-49 years of age, including healthcare personnel may receive either TIV or LAIV

  31. New Influenza Vaccine Recommendation • Children 6 months through 8 years being vaccinated for the first time should receive TWO doses • Some children do not return for the second dose • Beginning in influenza season 2007-2008 ACIP and AAP will recommend these children receive TWO doses the second vaccination year MMWR 2007;56 (RR-6)

  32. The Priming Effect • 1st dose primes the immune system • 2nd dose generates specific antibody response • Ideal if first dose given in the fall • Less ideal if first dose given in Spring, especially if a new B strain the following Autumn

  33. The Magic of Ninth Birthday • On or after ninth birthday Priming effect caused by natural infection thought to be significant. • Only one dose per season required Regardless of previous doses.

  34. Inactivated Influenza VaccineContraindications and Precautions • Contraindications • Severe allergic reaction to a vaccine component (e.g., egg) or following a prior dose of vaccine • Precaution • Moderate or severe acute illness • History of Guillain-Barre within 6 weeks of prior dose

  35. Egg allergy • Persons with a history of egg allergy who have experienced only hives after exposure to egg should receive influenza vaccine, with the following additional safety measures: • a) TIV rather than LAIV should be used. • b) Vaccine should be administered by a health-care provider who is familiar with the potential manifestations of egg allergy. • c) Vaccine recipients should be observed for at least 30 minutes for signs of a reaction after administration of each vaccine dose.

  36. Dividing and administering the vaccine by a two-step approach and skin testing with vaccine, are not necessary. • Persons who report having had reactions to egg involving such symptoms as angioedem persons should be referred to a physician with expertise in the management of allergic conditions.

  37. Live Attenuated Influenza VaccineContraindications and Precautions • Contraindications • Children <2 years of age • Persons >50 years of age • Pregnancy • Persons with underlying medical conditions including children and adolescents receiving chronic aspirin therapy • Immunosuppression • Precautions • History of Guillain-Barré Syndrome within 6 weeks of a previous dose of influenza vaccine

  38. Quadrivalent Influenza Vaccines • All currently available influenza vaccines are trivalent. • There are two antigenically distinct lineages of influenza B viruses referred to as Victoria and Yamagata lineages . Immunization against B virus strains of one lineage provides limited cross-protection against strains in the other lineage. • LAIV, FluMist (MedImmune). This vaccine would be available on 2013–14 . • Inactivated quadrivalent influenza vaccines currently are in development.

  39. Health Care Workers & Vaccine • Maximum efforts over many years to reach the goal that >90% of HCW be immunized for influenza have failed. • 2006-2007 national HCW influenza vaccine coverage rate 44%. • Significant effort by Occupational Health and Infection Control groups in recent years to maximize influenza vaccination. • In 2009,(98.4%) employees vaccinated.

  40. Healthy Habits • When Healthy: • Avoid close contact with those who are sick • Wash your hands often • Avoid touching your eyes, nose and mouth to decrease the spread of germs • When Ill: • Cover your mouth and nose with a tissue (or upper sleeve) when you sneeze or cough • Stay home from work or school when you are sick

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