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Pros and Cons of Universal Vaccination of the Children, including Potential Herd Immunity

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50% reduction in ALL winter deaths ... Red squares=H3N2 Blue triangles=H1N1/B ... Discuss use of live vaccine or 'flushot' for children ... – PowerPoint PPT presentation

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Title: Pros and Cons of Universal Vaccination of the Children, including Potential Herd Immunity


1
Pros and Cons of Universal Vaccination of the
Children, including Potential Herd Immunity
Most Critical Information Gaps that Need to be
Filled before Moving to Universal Vaccination of
Children

Lone Simonsen, NIAID, NIH, Bethesda, MD,
USA
Emory/CDC/NVPO Workshop, Atlanta, October 24-25,
2005
2
A bit of History
  • 1960 Prioritize high risk for vaccination
  • 1960-1994 concern was it working?
  • 1994- New generation cohort studies argued
    benefits were huge
  • 50 reduction in ALL winter deaths
  • 1996 CDC workshop addressed why no reduction in
    excess mortality had occurred as vaccine coverage
    soared
  • Healthy People Year 2000 efforts

3
Excess PI Mortality Rates age adjusted Younger
Elderly 65-74 years of age
Red squaresH3N2 Blue trianglesH1N1/B
4
Emerging evidence that VE was greatly
overestimated in cohort studies of elderly
  • 2004 Mangtani et al, JID
  • residual bias identified using seasonality
  • After adjustment, VE0 for all-cause mortality
  • 2005 Simonsen et al, Arch Int Med
  • no reduction in excess mortality since 1980
  • Only 5 of ALL winter deaths are attributable to
    influenza
  • 2005 Falsey et al, NEJM
  • Observational study of lab-confirmed influenza
    hospitalizations in the elderly (RSV control)
  • Found that VE 30 for influenza-hospitalization
  • 2005 Cochrane review, Jefferson et al, Lancet
  • Concluded problems with VE for elderly mortality
  • 2005 Jackson et al (2 papers in review)
  • Demonstration of residual self-selection bias
  • max VE for mortality obtain before influenza
    circulates

5
A Placebo-controlled RCT set in 911 younger
Dutch Elderly
plt0.05
Gowaert 1994
6
Cannot separate discussion of universal
vaccination from knowing
  • 1.How successful is current influenza control
    efforts of vaccinating high risk groups
  • Elderly? High-risk? Childrenlt23mo?
  • Can unchanging mortality rates be explained by
    immune senescence? By failure to reach those at
    highest risk?
  • If we believe cohort studies then there is no
    reason for seeking novel vaccination strategies
    that provide herd immunity
  • Need for consideration of residual bias
  • Need for studies of VE in elderly gt75 years
  • Need for randomized clinical trials in elderly,
    perhaps head-to-head if not placebo-controlled

7
Cannot separate discussion of universal
vaccination from considering
  • 2. How to prioritize indirect versus direct
    protection in seasons when there is vaccine
    shortage?
  • in pandemics preparedness planning?
  • for epidemic seasons?
  • How can universal vaccination program demonstrate
    that indirect benefits took place?
  • …. a common curse for public health….

8
Cannot separate discussion of universal
vaccination from
  • The need to modernize health metrics used for
    measuring influenza preventable disease burden
    and to define priority groups
  • A 99-year old death counts as much as a child
  • Consider Years of Life Lost (YLL) and DALYs like
    other disases?
  • Consider using new prioritization approach
    Influenza risk x VE

9
Gaps
  • Reach agreement on effectiveness of current
    control efforts
  • Discuss universal immunization in context of
    vaccine shortage issues
  • Align with pandemic planning ?
  • Discuss use of live vaccine or flushot for
    children
  • LAIV seems the better choice - broader and
    longer-lasting protection no vaccine shortage in
    LAIV so far
  • Modern health metrics for setting vaccine
    priorities
  • Counting YLL (and not deaths) tend to favour
    younger pop
  • How to demonstrate indirect protection success
  • lives saved by herd immunity are not tangible or
    visible and difficult to measure
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