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Influenza and Influenza Vaccine

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Epidemiology and Prevention of Vaccine-Preventable Diseases ... virus Trivalent (H3N2, H1N1, B) Efficacy Varies by similarity to circulating strain, age ... – PowerPoint PPT presentation

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Title: Influenza and Influenza Vaccine


1
  • Influenza and Influenza Vaccine

Epidemiology and Prevention of Vaccine-Preventable
Diseases National Immunization Program Centers
for Disease Control and Prevention
Revised March 2002
2
Influenza
  • Highly infectious viral illness
  • Epidemics reported since at least 1510
  • At least 4 pandemics in 19th century
  • Estimated 21 million deaths worldwide in pandemic
    of 1918-1919
  • Virus first isolated in 1933

3
Influenza Virus
  • Single-stranded RNA virus
  • Family Orthomyxoviridae
  • 3 types A, B, C
  • Subtypes of type A determined by hemagglutinin
    and neuraminidase

4
Influenza Virus Strains
  • Type A- moderate to severe illness - all age
    groups
  • - humans and other animals
  • Type B- milder epidemics - humans only -
    primarily affects children
  • Type C- rarely reported in humans
  • - no epidemics

5
  • Influenza Virus

6
Influenza Antigenic Changes
  • Structure of hemagglutinin (H) and neuraminidase
    (N) periodically change
  • Shift Major change, new subtype
  • Exchange of gene segment
  • May result in pandemic
  • Drift Minor change, same subtype
  • Point mutations in gene May result in
    epidemic

7
Examples of Influenza Antigenic Changes
  • Antigenic shift
  • H2N2 circulated in 1957-1967
  • H3N2 appeared in 1968 and completely replaced
    H2N2
  • Antigenic drift
  • In 1997, A/Wuhan/359/95 (H3N2) virus was dominant
  • A/Sydney/5/97 (H3N2) appeared in late 1997 and
    became the dominant virus in 1998

8
  • Influenza Type A Antigenic Shifts

9
Impact of Pandemic Influenza
  • 200 million people could be affected
  • Up to 40 million require outpatient visits
  • Up to 700,000 hospitalized
  • 89,000 - 200,000 deaths

10
Influenza Pathogenesis
  • Respiratory transmission of virus
  • Replication in respiratory epithelium with
    subsequent destruction of cells
  • Viremia usually not demonstrable
  • Viral shedding in respiratory secretions for 5-10
    days

11
Influenza Clinical Features
  • Incubation period 2 days (range 1-5 days)
  • Severity of illness depends on prior experience
    with related variants
  • Abrupt onset of fever, myalgia, sore throat,
    nonproductive cough, headache

12
Influenza Complications
  • Pneumonia
  • primary influenza
  • secondary bacterial
  • Reye syndrome
  • Myocarditis
  • Death 0.5-1 per 1000 cases

13
Impact of Influenza
  • Highest rates of hospitalization among young
    children and person gt65 years
  • Average of 114,000 influenza-related excess
    hospitalizations per year since 1969
  • 57 of all hospitalizations among persons lt65
    years of age
  • Greater number of hospitalizations during type A
    (H3N2) epidemics

14
Impact of Influenza
  • 20,000 excess deaths in each of 11 epidemics
    between 1972 and 1995
  • gt40,000 excess deaths in 6 epidemics
  • gt90 of deaths among persons gt65 years of age

15
Influenza Diagnosis
  • Clinical and epidemiological characteristics
  • Isolation of influenza virus from clinical
    specimen (e.g., nasopharynx, throat, sputum)
  • Significant risk in influenza IgG by serologic
    assay
  • Direct antigen testing for type A virus

16
Influenza Epidemiology
  • Reservoir Human, animals (type A only)
  • Transmission Respiratory
    Probably airborne
  • Temporal pattern Peak December - March in
    temperate area May occur earlier or
    later
  • Communicability Maximum 1-2 days before
    to 4-5 days after onset

17
Month of Peak Influenza Activity United States,
1976-2001
18
Influenza Vaccine
  • Composition Split (subvirion) virus Trivalent
    (H3N2, H1N1, B)
  • Efficacy Varies by similarity to
  • circulating strain, age,
  • underlying illness
  • Duration ofImmunity lt1 year
  • Schedule 1 dose annually

2 doses for first vaccination of children lt9
years
19
Influenza Vaccine Efficacy
  • 70 to 90 effective among persons lt65 years of
    age
  • 30-40 effective among frail elderly persons
  • 50-60 effective in preventing hospitalization
  • 80 effective in preventing death

20
  • Influenza and Complications Among Nursing Home
    Residents

RR1.9
RR2.0
RR2.5
RR4.2
Genesee County, MI, 1982-1983
21
Timing of Influenza Vaccine Programs
  • Influenza activity peaks between late December
    and early March
  • Optimal time for vaccination programs October
    through November
  • First available vaccine should be targeted to
    persons at highest risk of complication of
    influenza

22
Timing of Influenza Vaccine Programs
  • Actively target vaccine available in September
    and October to persons at increase risk of
    influenza complications, children lt9 years, and
    health care workers
  • Vaccination of all other groups should begin in
    November
  • Continue vaccinating through December and later,
    as long as vaccine is available

23
Influenza Vaccine 2001-2002
  • A/Moscow/10/99 (H3N2)
  • A/New Caledonia/20/99 (H1N1)
  • B/Sichuan/379/99

24
  • Influenza Vaccine Schedule

25
Influenza Vaccine Recommendations
  • All persons 50 years of age or older
  • Persons gt6 months of age with chronic illness
  • Residents of long-term care facilities
  • Pregnant women
  • Persons 6 months to 18 years receiving chronic
    aspirin therapy

26
Influenza Vaccine Recommendations
  • Routine annual influenza vaccination for persons
    50 years and older
  • Up to a third of persons 50-64 years have high
    risk conditions
  • Only 35 received influenza vaccine in 1999
  • May increase coverage in HCWs
  • Reduced sick days

27
Influenza Vaccine Recommendations
  • Persons with the following chronic illnesses
    should be considered for influenza vaccine
  • pulmonary (e.g., asthma, COPD)
  • cardiovascular (e.g., CHF)
  • metabolic (e.g., diabetes)
  • renal dysfunction
  • hemoglobinopathies
  • immunosuppression, including HIV
  • infection

28
Pregnancy and Influenza Vaccine
  • Risk of hospitalization 4 times higher than
    nonpregnant women
  • Risk of complications comparable to nonpregnant
    women with high risk medical conditions
  • Vaccination recommended if gt14 weeks gestation
    during influenza season

29
HIV Infection and Influenza Vaccine
  • Persons with HIV at higher risk of complications
    of influenza
  • Vaccine induces protective antibody titers in
    many HIV infected persons
  • Transient increase in HIV replication reported
  • Vaccine will benefit many HIV-infected persons

30
Influenza Vaccination of Children
  • Children lt24 months at increased risk of
    hospitalization
  • Vaccination of healthy children 6-23 months is
    encouraged
  • Vaccination of household contacts and out-of-home
    caretakers is encouraged

31
Influenza Vaccine Recommendations
  • Health care providers, including home care
  • Employees of long-term care facilities
  • Household members of high-risk persons (including
    children 0-23 months)

32
In the 2000 National Health Interview Survey,
only 38 of health care workers reported
receiving influenza vaccine in the previous 12
months.
33
Influenza Vaccination of HCWs
  • Educate HCWs about the benefits of vaccination
    for themselves, their families, and their
    patients
  • Educate staff about vaccine adverse reactions
  • Provide free vaccine at the work site to all
    employees, including night and weekend staff

34
Influenza Vaccine Recommendations
  • Providers of essential community services
  • Foreign travelers
  • Students
  • Anyone who wishes to reduce the likelihood of
    becoming ill from influenza

35
Influenza Vaccine Adverse Reactions
  • Local reactions 15-20
  • Fever, malaise uncommon
  • Allergic reactions rare
  • Neurological very rare reactions

36
Influenza VaccineContraindications and
Precautions
  • Severe allergy to vaccine component (e.g., egg,
    thimerosal) or following prior dose of vaccine
  • Moderate to severe acute illness

37
Influenza VaccineStrategies to Improve Coverage
  • Ensure systematic and automatic offering of
    vaccine to high-risk groups
  • Educate health care providers and patients
  • Address concerns about adverse events
  • Emphasize physician recommendation

38
Influenza VaccineMissed Opportunities
  • Up to 75 of persons at high risk for influenza
    or who die from pneumonia and influenza may have
    received care in a physician's office in the
    previous year.
  • In one study all non-nursing home persons who
    died from pneumonia or influenza had at least one
    medical visit in the previous year.

39
Influenza Antiviral Agents
  • Amantadine and rimantadine
  • effective against influenza A only
  • approved for treatment and prophylaxis
  • Zanamivir and oseltamivir
  • neuraminidase inhibitors
  • effective against influenza A and B
  • oseltamivir approved for prophylaxis

40
Live-attenuated, Cold-adapted Intranasal
Influenza Vaccine
  • Vaccine efficacy 93 among children for influenza
    A (H3N2) and influenza B
  • Vaccinated children had 21 fewer febrile
    illnesses
  • Vaccinated children had 30 fewer episides of
    febrile otitis media

Belshe et al, NEJM 19983381405-12
41
Live-attenuated, Cold-adapted Intranasal
Influenza Vaccine
  • Safe and effective in children
  • May increase influenza vaccine coverage among
    high-risk children
  • Cost-effectiveness and impact of wider use among
    children unknown

42
Influenza Surveillance
  • Monitor prevalence of circulating strains and
    detect new strains
  • Rapidly detect outbreaks
  • Assist disease control through rapid preventive
    action
  • Estimate influenza-related morbidity, mortality
    and economic loss

43
National Immunization Program
  • Hotline 800.232.2522
  • Email nipinfo_at_cdc.gov
  • Website www.cdc.gov/nip
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