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Influenza and Influenza Vaccine


Higher mortality during seasons when influenza type A (H3N2) viruses predominate ... Average of more than 200,000 influenza-related excess hospitalizations ... – PowerPoint PPT presentation

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Title: 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
Note to presenters Images of vaccine-preventable
diseases are available from the Immunization
Action Coalition website at http//www.vaccineinfo
  • Highly infectious viral illness
  • First pandemic in 1580
  • At least 4 pandemics in 19th century
  • Estimated 21 million deaths worldwide in pandemic
    of 1918-1919
  • Virus first isolated in 1933

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

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

  • Influenza Virus

Influenza Antigenic Changes
  • Hemagglutinin and neuraminidase antigens change
    with time
  • Changes occur as a result of point mutations in
    the virus gene, or due to exchange of a gene
    segment with another subtype of influenza virus
  • Impact of antigenic changes depend on extent of
    change (more change usually means larger impact)

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

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
  • A/Fujian/411/2002 (H3N2) appeared in late 2003
    and caused widespread illness in 2003-2004

  • Influenza Type A Antigenic Shifts

Severity of Pandemic Moderate Severe
Severe Moderate Mild
Year 1889 1918 1957 1968 1977
Subtype H3N2 H1N1 H2N2 H3N2 H1N1
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

Influenza Pathogenesis
  • Respiratory transmission of virus
  • Replication in respiratory epithelium with
    subsequent destruction of cells
  • Viremia rarely documented
  • Viral shedding in respiratory secretions for 5-10

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

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

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

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

Impact of Influenza
  • Rates of hospitalization among children 2 years
    and younger are similar to those of persons 65
    and older with high-risk medical conditions
  • Children 24 through 59 months of age are at
    increased risk for influenza-related clinic and
    emergency department visits

Hospitalization Rates for Influenza By Age and
Risk Group
Rate (not high-risk) 496-1038 186 86 41 23-25
13-23 125-228
Rate (high-risk) 1900 800 320 92 56-110 392-6
35 399-518
Age Group 0-11 mos 1-2 yrs 3-4 yrs 5-14
yrs 15-44 yrs 45-64 yrs gt65 yrs
Data from several studies 1972 - 1995
Hospitalizations per 100,000 population
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

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

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

Pneumonia and Influenza Mortalityfor 122 U.S.
CitiesWeek Ending 05/17/2008
Epidemic Threshold
Seasonal Baseline
50 10 20 30 40 50
10 20 30 40 50 10 20
30 40 50 10 20 30
40 50 10
Month of Peak Influenza Activity United States,
MMWR 20065522
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

Composition of the 2009-20010 Influenza Vaccine
  • A/Brisbane/59/2007 (H1N1)
  • A/Brisbane/10/2007 (H3N2)
  • B/Brisbane/60/2008

manufacturers may use strains that are
antigenically identical to the selected strains.
Inactivated Influenza Vaccines Available in
vaccines approved for children younger than 4
years all multi-dose vials contain thimerosal as
a preservative
Inactivated Influenza Vaccines Available in
all multi-dose vials contain thimerosal as a
Transmission of LAIV Virus
  • LAIV replicates in the nasopharyngeal mucosa
  • Mean shedding of virus 7.6 days longer in
  • One instance of transmission of vaccine virus
    documented in a child care setting
  • Transmitted virus retained attenuated,
    cold-adapted, temperature-sensitive
  • No transmission of LAIV reported in the U.S.

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

  • Influenza and Complications Among Nursing Home

Inactivated influenza vaccine. Genesee County,
MI, 1982-1983
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
  • Decreased fever and OM in vaccine recipients who
    developed influenza

LAIV Efficacy in Healthy Adults
  • 20 fewer severe febrile illness episodes
  • 24 fewer febrile upper respiratory illness
  • 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

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

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

Timing of Influenza Vaccine Programs
  • Persons planning organized vaccination campaigns
    should consider scheduling these events after at
    least mid-October
  • Scheduling campaigns after mid-October will
    minimize the need for cancellations because
    vaccine is unavailable
  • Continue to offer influenza vaccine in December
  • Providers should continue to vaccinate throughout
    influenza season

  • Inactivated Influenza Vaccine Schedule

Dose 0.25 mL 0.50 mL 0.50 mL
Age Group 6-35 mos 3-8 yrs gt9 yrs
No. Doses 1 or 2 1 or 2 1
Only one dose is needed if the child received 2
doses of influenza vaccine during the previous
influenza season
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
Influenza Vaccination of Children 6 Months
Through 8 Years Of Age
  • Previous vaccination
  • One dose last year
  • One dose in each of the last 2 years
  • One dose 3 years ago
  • One dose in each of the last 3 years
  • Vaccine THIS year
  • Two doses
  • One dose
  • One dose
  • One dose

children 9 years and older should receive only
one dose of influenza vaccine per year regardless
of the number of doses in previous years
Inactivated Influenza Vaccine Recommendations
  • All persons 50 years of age or older
  • Healthy children 6 months through 18 years of age
  • Residents of long-term care facilities
  • Pregnant women
  • Persons 6 months through 18 years receiving
    chronic aspirin therapy
  • Persons 6 months of age and older with chronic

Influenza Vaccination of Children
  • Children 6-59 months at increased risk of
    hospitalization and physician visits
  • Inactivated influenza vaccination of healthy
    children 6-59 months is recommended
  • Vaccination of household contacts and other
    caregivers of children younger than 59 months is

Inactivated Influenza Vaccine Recommendations
  • Persons with the following chronic illnesses
    should be considered for inactivated influenza
  • pulmonary (e.g., asthma, COPD)
  • cardiovascular (e.g., CHF)
  • metabolic (e.g., diabetes)
  • renal dysfunction
  • hemoglobinopathy
  • immunosuppression, including HIV infection
  • any condition that can compromise respiratory
    function or the handling of respiratory

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 if pregnant
    during influenza season
  • Vaccination can occur during any trimester

HIV Infection and Inactivated Influenza Vaccine
  • Persons with HIV at increased risk of
    complications of influenza
  • TIV induces protective antibody titers in many
    HIV infected persons
  • TIV will benefit many HIV-infected persons
  • Do not administer LAIV to persons with HIV

Influenza Vaccine Recommendations
  • Healthcare providers, including home care
  • Employees of long-term care facilities
  • Household contacts of high-risk persons

LAIV should not be administered to healthcare
workers who have contact with severely
immunosuppressed persons who require
hospitalization and care in a protective
Influenza Vaccine Recommendations
  • Providers of essential community services
  • Persons traveling outside the U.S.
  • Persons in institutional settings (e.g., students
    who reside in a dormitory persons in a
    correctional facility)
  • Anyone who wishes to reduce the likelihood of
    becoming ill from influenza

these groups may receive TIV, and some may be
eligible for LAIV
In the 2004 National Health Interview Survey,
only 40 of healthcare personnel reported
receiving influenza vaccine in the previous 12
Influenza Vaccination of HCPs
  • Educate HCWs about the benefits of vaccination
    for themselves, their families, and their
  • Educate staff about vaccine adverse reactions
  • Provide free vaccine at the work site to all
    employees, including night and weekend staff

Live Attenuated Influenza VaccineSchedule
  • Age Group
  • 2 - 8 years, no previous influenza vaccine
  • 2 - 8 years, previous influenza vaccine
  • 9 - 49 years
  • Number of Doses
  • 2
  • (separated by 4 weeks)
  • 1
  • 1

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
Simultaneous Administration of LAIV and Other
  • Inactivated vaccines can be administered either
    simultaneously or at any time before or after
  • Other live vaccines can be administered on the
    same day as LAIV
  • Live vaccines not administered on the same day
    should be administered at least 4 weeks apart

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

Live Attenuated Influenza VaccineAdverse
  • 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

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 Barre syndrome within 6
    weeks following a previous dose of TIV

Live Attenuated Influenza VaccineContraindication
s 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
Live Attenuated Influenza VaccineContraindication
s 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
  • Moderate or severe acute illness

These persons should receive inactivated
influenza vaccine
Live Attenuated Influenza Vaccination of Children
2-4 Years of Age
  • Clinicians and immunization programs should avoid
    use of LAIV in children with asthma or a recent
    wheezing episode
  • Consult the medical record, when available, to
    identify children 2 through 4 years of age with
    asthma or recurrent wheezing that might indicate

Live Attenuated Influenza Vaccination of Children
2-4 Years of Age
  • Parents or caregivers of children 2-4 years
    should be asked
  • In the past 12 months, has a healthcare
    provider ever told you that your child had
    wheezing or asthma?
  • Children whose parents or caregivers answer "yes"
    to this question, or whose medical record notes
    asthma or a wheezing episode within the past 12
    months, should not receive LAIV
  • Inactivated influenza vaccine should be
    administered to children with asthma or possible
    reactive airways diseases

Influenza VaccineStorage and Handling
  • Both types of influenza vaccine must be stored at
    refrigerator temperature (35-46F, 2-8C)
  • Neither vaccine should be frozen
  • If LAIV is inadvertently frozen the vaccine
    should be placed at refrigerator temperature and
    used as soon as possible

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

Influenza Antiviral Agents
  • Amantadine and rimantadine
  • Not recommended because of documented resistance
    in U.S. influenza isolates
  • Zanamivir and oseltamivir
  • neuraminidase inhibitors
  • effective against influenza A and B
  • should be used if an influenza antiviral drug is
    indicated for chemoprophylaxis or treatment

see influenza ACIP statement or CDC influenza
website for details
Influenza Surveillance
  • Monitor prevalence of circulating strains and
    detect new strains
  • Estimate influenza-related morbidity, mortality
    and economic loss
  • Rapidly detect outbreaks
  • Assist disease control through rapid preventive

CDC Vaccines and ImmunizationContact Information
  • Telephone 800.CDC.INFO
  • Email
  • Website