epidim. & control measles & rubella
TRANSCRIPT
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Epidemiology and Global Control of Measles and
RubellaPeter M. Strebel, MBChB
National Immunization ProgramCenters for Disease Control and Prevention
Global Vaccine Research Forum Montreux, Switzerland
8-10 June 2004
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Aim and Outline
Aim: introduction to session
Outline:
– Global disease burden
– Epidemiologic characteristics
– Vaccine properties
– Control strategies
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Estimated Global Disease Burden: Vaccine Preventable Diseases Among Children
Disease Global BurdenMeasles (2002) 610,000 deathsHib 450,000 deathsPertussis 285,000 deathsNeonatal tetanus 200,000 deathsCRS (1996) 110,000 casesYellow fever 30,000 deathsDiphtheria 5,450 deathsParalytic Polio (2003) 784 cases
Source: World Health Report 2004; data for 2002; Cutts & Vynnycky Int J Epidemiol 1999
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Disease Control Goals
Measles RubellaGlobal Eradication No NoGlobal Control Yes* NoRegional Elimination
Americas 2000 2010E. Mediterranean 2010Europe 2010W. Pacific Date to be set
*WHA 2003: 50% reduction in deaths by 2005 vs. 1999
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Estimated measles deaths by WHO region, 2001
050,000
100,000150,000200,000250,000300,000350,000400,000450,000500,000
AFRO SEARO EMRO WPRO EURO PAHO
>98% occur ineligible
countries
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WHO/UNICEF priority countriesWHO/UNICEF priority countries
for measles mortality reduction, 2001for measles mortality reduction, 2001
45 countries representing 94 % of all measles deaths45 countries representing 94 % of all measles deaths
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Countries/territories using a rubella containing vaccine in their NIP, 2004*
Source: WHO Department of Vaccines and Biologicals, December 2003
Yes (124 countries/territories, 57%, 99% children one year old in the Americas)
No ( 91 countries/territories, 43%)
The boundaries and names shown and the designations used on this map do not imply the expression of any opinion whatsoever on the part of the World Health Organization concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. Dotted lines on maps represent approximate border lines for which there may not yet be full agreement.
Haiti
* May 2004 in the Americas
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Epidemiologic Characteristics
Feature Measles RubellaOccurrence worldwide worldwideReservoir human humanTransmission respiratory respiratory
person to person person to personCommunicability high* moderate**Seasonality late winter late winterInter-epidemic interval† 2-3 years 6-9 years
*airborne droplet nuclei**subclinical cases transmit and CRS cases may transmit for ~year† prevaccine era
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Contagiousness of Common Childhood Communicable Diseases
Source: Anderson & May, Nature 1985, 318:323-9.
Average Age at Infection (years)
Disease IndustrializedLess
Industrialized
Measles
Mumps Chickenpox RubellaPolio
5-6 (USA, 1955-8)
6-7 (England, 1975-7)6-8 (USA, 1912-28)9-10 (USA, 1966-8)12-17 (USA, 1955)
1-2 (Senegal, 1964)1-2 (Bangkok, 1967)
2-3 (Gambia, 1976)
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Herd Immunity Threshold
• Younger average age of infection, more contagious the disease
• More contagious, higher herd immunity level needed
• HI threshold = 1-1/Ro
Where Ro (basic reproductive no.) =average no. secondary cases in a fully susceptible population
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Comparison of Herd Immunity Thresholds
Basic Reproductive number Ro 12 – 18 Ro 6-10
Herd Immunity threshold 92-95% 83-90%
Measles Rubella
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Measles and Rubella Vaccines
Feature Measles RubellaComposition Live virus* Live virus*Effectiveness 85% (9m) 95-100% (9m)
95% (12m)Waning antibodies Yes YesDuration of protection Lifelong LifelongSchedule 2 doses 1 dose
(or 2 opportunities)
*attenuated live virus
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Adverse Events Associated with Measles and Rubella Vaccines
Event Measles/RubellaFever 5-15%Rash 5%Febrile seizure* 1/3000Thrombocytopenia 1/30,000Joint symptoms** 1%
25% (adult female)Anaphylaxis ~1/1,000,000Encephalitis ~1/1,000,000
*No association with residual febrile disorder**No association with chronic arthropathy
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Control Strategies
• Country examples– Finland– Albania– PAHO Region
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Purpose of Vaccination
Goal Measles RubellaControl protect individual protect individual
prevent deaths prevent CRSyoung children pregnant women
Elimination protect community protect community stop transmission stop transmissionpopulation immunity population immunity
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Finnish Experience
• 1982 2 dose MMR strategy– At 14-18m and 6y
• Very strong public health system• Very high coverage (~95%) with each dose• 1986 last CRS case • 1993 measles eliminated • 1996 last rubella case
Peltola et al., NEJM, 1994;331:1397-1402
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Albanian Experience
• Population 3.4 mil, isolated until 1990s• No rubella vaccination prior to 2000• Nov 2000 MR mass campaign
– 1-14 years– Coverage >95%
• Jan 2001 MMR at 12m and 5 years• Sep 2001 MR women 16-35y (routine services)
– Ongoing post-partum vaccination
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Reported Incidence of Rubella and CRS in Albania
• 1960 rubella notifiable• Pre-vaccine era
– Outbreaks every 5-7 years– School children, majority <15 years
• 2001 10 rubella cases• 2002-3 zero confirmed measles or rubella cases• 2002-3 zero CRS cases
Measles and rubella eliminated ??
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PAHO ExperienceVaccination Strategies for Elimination
Measles
• Catch-up campaign (1-14y)
• Keep-up - achieving and maintaining high routine vaccination coverage using MMR vaccine
• Follow-up campaigns at least every 4 years, targeting 1-4 year olds, using MR vaccine
Rubella
• Introduction of MMR into the routine childhood program
• Adults males and females mass campaigns using MR vaccine
(The upper age range for men and women targeted for vaccination will depend on the year of the introduction the vaccine, follow-up campaigns, epidemiology and fertility rates in their country.)
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Vaccination Coverage & Reported Number of Measles Cases, The Americas, 1990 – 2003*
0
50000
100000
150000
200000
250000
300000
90 91 92 93 94 95 96 97 98 99 2000 2001 2002 20030
20
40
60
80
100
Cases Coverage
Source: PAHO/WHO: Data sent by countries; 50 cases confirmed as of 10 April 2004
Catch-up campaigns
Follow-up campaigns
Routine vaccination coverage (%
)Con
firm
ed c
ases
(tho
usan
ds)
PAHO
105
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Confirmed Measles in the Americas by Rash Onset and Genotypes, January 2001 - May 2004*
0
50
100
150
200
250
1 5 9 13 17 21 25 29 33 37 41 45 49 1 5 9 13 17 21 25 29 33 37 41 45 49 1 5 9 13 17 21 25 29 33 37 41 45 49 1 5 9 13 17
Genotypes
D9D6
H1 (Import, Asia)Others, unknown
*Source: Country reportsAs of EPI week 19
EPI Weeks
Cas
es
2001 2002 2003
End
of tr
ansm
issi
on o
f gen
otyp
e D
6
End
of tr
ansm
issi
on o
f gen
otyp
e D
92004
Importations
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Annual number of reported rubella cases and number of countries reporting rubella, the Americas, 1982-2004*
020406080
100120140
82 84 86 88 90 92 94 96 98 '00 '02 '04
Year
Rep
orte
d ca
ses
Thou
sand
s
0
10
20
30
40 Countries reporting
Cases Countries reportingSource: PAHO-MoH*As of EPI Week 19
Measleseradication goal is
set
Accelerated Rubella Control
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0
50,000
100,000
150,000
200,000
250,000
300,000
82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 '00 '01 '02 '030
20,000
40,000
60,000
80,000
100,000
120,000
140,000
* Three year moving averages
Reported rubella cases
Rep
orte
d m
easl
es c
ases
Trends in reported measles and rubella cases
Region of the Americas, 1982-2003*
Measles Rubella
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2 12
35020
0 040
102030405060708090
80 82 84 86 88 90 92 94 96 98 00 2Year
Cas
es (
in th
ousa
nds)
02004006008001,0001,2001,4001,6001,8002,000
Dea
ths
Cases Deaths
Catch-upCampaigns
Reported measles cases & deaths by year, 7 Southern African Countries, 1980-2003
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Partnership for Reduction of Measles Mortality in Africa 2001–2003
• Partners: ARC, UNF, UNICEF, WHO & CDC
•Measles campaigns in 29 countries
•112 million children immunized
•Est.170,000 deaths averted annually*
*WHO Weekly Epi Rec, 2004
Nationwide
Sub-national
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Percent reduction in estimated measles deaths by WHO Percent reduction in estimated measles deaths by WHO region between 1999 and 2002region between 1999 and 2002
-40-35-30-25-20-15-10
-50
AFR EMR SEAR Others Global
Region
% r
educ
tion
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Summary
• Significant preventable disease burden
• Due to failure to vaccinate with measles and rubella vaccines
• Extensive experience with safety and effectiveness
• Elimination possible with existing vaccines and strategies– High coverage 2 dose and 2nd opportunity strategies
• As measles is controlled rubella “emerges” as a public health problem
• Progress toward 2005 mortality reduction goal
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Acknowledgements
Drs Jon Andrus and Carlos Castillo, PAHO
Drs Brad Hersh and Susan Robertson, WHO/HQ
Drs Susan Reef and Mark Papania, NIP, CDC