Epidemiology of MeaslesEpidemiology of Measles

Prof. Ashry Gad MohamedProf. Ashry Gad Mohamed

Prof. of EpidemiologyProf. of Epidemiology

Highly contagious viral illnessHighly contagious viral illness First described in 7th centuryFirst described in 7th century Near universal infection of childhood in Near universal infection of childhood in

prevaccination eraprevaccination era Common and often fatal in developing Common and often fatal in developing

areasareas

No second opportunity for measles immunization ( 45 )No second opportunity for measles immunization ( 45 )

94 % of all measles deaths in 200094 % of all measles deaths in 2000

Leading killer of childrenLeading killer of children

We know WHERE . . .We know WHERE . . . 0

50,000100,000150,000200,000250,000300,000350,000400,000450,000500,000

AFR SEAR EMR WPR EUR AMR

Cases 2005Cases 2005

. An estimated 345 000 people, the majority . An estimated 345 000 people, the majority of them children, died from measles in 2005.of them children, died from measles in 2005.

From 2000 to 2005, more than 360 million From 2000 to 2005, more than 360 million children globally received measles vaccine.children globally received measles vaccine.

Global ProgressGlobal ProgressMeasles Mortality Reduction by 50% by 2005 Measles Mortality Reduction by 50% by 2005

(compared to 1999 : 875,000 deaths)(compared to 1999 : 875,000 deaths)

0

100000

200000

300000

400000

500000

600000

700000

800000

900000

1999 2000 2001 2002 2003 2004 2005

Estimated Measles Mortality by YearEstimated Measles Mortality by Year

Deaths from MeaslesDeaths from Measles

Africa 126 000 [93 000 - 164 000] Africa 126 000 [93 000 - 164 000] Americas <1 000 [-] Americas <1 000 [-] Eastern Mediterranean 39 000 [26 000 - 53 000] Eastern Mediterranean 39 000 [26 000 - 53 000] European <1 000 [-] European <1 000 [-] South-East Asia 174 000 [126 000 - 233 000] South-East Asia 174 000 [126 000 - 233 000] Western Pacific 5000 [3000 - 8000] Western Pacific 5000 [3000 - 8000] TOTAL 345 000 [247 000 - 458 000]TOTAL 345 000 [247 000 - 458 000]

Measles Mortality Reduction in EMRO Region, 1999-2004 EMRO

0

20,000

40,000

60,000

80,000

100,000

120,000

1999 2000 2001 2002 2003 2004

Year

Esti

mate

d D

eath

s

LibyaEgypt

Sudan

Morocco

Tunisia

Somalia

Saudi Arabia

Yemen

Oman

Djibouti

Pakistan

AfghanistanIranIraq

Syria

Jordan

LebanonPalestine

QatarUAE Bahrain

Kuwait

Percent reduction in estimated measles Percent reduction in estimated measles deaths by WHO region between 1999 and deaths by WHO region between 1999 and

20022002

-40

-35

-30

-25

-20

-15

-10

-5

0

AFR SEAR WPR EMR EUR Global

Region

% r

edu

ctio

n

Measles Case Counts and Measles Case Counts and Coverage Saudi Arabia 1983-2004Coverage Saudi Arabia 1983-2004

0100020003000400050006000700080009000

100001100012000

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

Year

Cas

es

828486889092949698100

Per

cent

cov

erag

e

There was a marked reduction in the epidemic There was a marked reduction in the epidemic peak from 500/100 000 in the 1970s to < 80/100 peak from 500/100 000 in the 1970s to < 80/100 000 in the 1990s. 000 in the 1990s.

Incidence among children 6–8 months of age fell Incidence among children 6–8 months of age fell from > 400/100 000 before the implementation of from > 400/100 000 before the implementation of the new policy to < 100/ 100 000 in 1997. the new policy to < 100/ 100 000 in 1997. Similarly, among children aged 9–11 months, the Similarly, among children aged 9–11 months, the number of cases fell from > 200/100 000 before number of cases fell from > 200/100 000 before the implementation of the new policy to <100/100 the implementation of the new policy to <100/100 000 in 1997. 000 in 1997.

2005 373cases2005 373cases

Measles PathogenesisMeasles Pathogenesis

Respiratory transmission of virusRespiratory transmission of virus Replication in nasopharynx and regional Replication in nasopharynx and regional

lymph nodeslymph nodes Primary viremia 2-3 days after exposurePrimary viremia 2-3 days after exposure Secondary viremia 5-7 days after exposure Secondary viremia 5-7 days after exposure

with spread to tissueswith spread to tissues

Measles Clinical FeaturesMeasles Clinical Features

Incubation period 10-12 daysIncubation period 10-12 days

Stepwise increase in fever to Stepwise increase in fever to 103°F or higher103°F or higher

Cough, coryza, conjunctivitis Cough, coryza, conjunctivitis , malaise, , malaise, sneezing, rhinitis, congestionsneezing, rhinitis, congestion

Koplik spotsKoplik spots

Prodrome

Koplik's spots, are pathognomonic in measles, appear on the buccal and lower labial mucosa opposite the lower molars as White spots inside the mouth

Measles Clinical FeaturesMeasles Clinical Features

2-4 days after prodrome, 14 days after 2-4 days after prodrome, 14 days after exposureexposure

Maculopapular, becomes confluentMaculopapular, becomes confluent Begins on face and headBegins on face and head Persists 5-6 daysPersists 5-6 days Fades in order of appearanceFades in order of appearance

Rash

Child has a rash caused by measles

Measles rash covering child's arms and stomach

ConditionConditionDiarrheaDiarrheaOtitis mediaOtitis mediaPneumoniaPneumoniaEncephalitisEncephalitisHospitalizationHospitalizationDeathDeath

Percent reported876

0.1180.2

Measles ComplicationsMeasles Complications

Based on 1985-1992 surveillance data

0

5

10

15

20

25

30

<5 5-19 20+

Age group (yrs)

Perc

en

t

Pneumonia Hospitalization

Measles Complications by Age GroupMeasles Complications by Age Group

Measles Clinical Case DefinitionMeasles Clinical Case Definition

Generalized rash lasting >3 days, Generalized rash lasting >3 days, andand

Temperature 101°F (>38.3°C), andTemperature 101°F (>38.3°C), and Cough or coryza or conjunctivitisCough or coryza or conjunctivitis

Measles Laboratory DiagnosisMeasles Laboratory Diagnosis

Isolation of measles virus from a clinical Isolation of measles virus from a clinical specimen (e.g., nasopharynx, urine)specimen (e.g., nasopharynx, urine)

Significant rise in measles IgG by any Significant rise in measles IgG by any standard serologic assay (e.g., EIA, HA)standard serologic assay (e.g., EIA, HA)

Positive serologic test for measles IgM Positive serologic test for measles IgM antibodyantibody

Measles VirusMeasles Virus

Paramyxovirus (RNA)Paramyxovirus (RNA) One antigenic typeOne antigenic type Rapidly inactivated by heat and lightRapidly inactivated by heat and light

ReservoirReservoir

HumanHuman Incubation period. Incubation period.

Clinical caseClinical case

No animal reservoirNo animal reservoir

TransmissionTransmission The virus spreads by the respiratory The virus spreads by the respiratory

route via aerosol droplets and route via aerosol droplets and respiratory secretions which can remain respiratory secretions which can remain infectious for several hours.infectious for several hours.

The infection is acquired through the The infection is acquired through the upper respiratory tract or conjunctivaupper respiratory tract or conjunctiva

In the pre-vaccination era, the maximum In the pre-vaccination era, the maximum incidence was seen in children aged 5 - 9 incidence was seen in children aged 5 - 9 years. By the age of 20, approximately years. By the age of 20, approximately 99% of subjects have been exposed to 99% of subjects have been exposed to the virus. the virus.

With the introduction of vaccine, measles With the introduction of vaccine, measles infection has shifted to the teens in infection has shifted to the teens in countries with an efficient programmecountries with an efficient programme..

In contrast, in third world countries, measles In contrast, in third world countries, measles infection has its greatest incidence in infection has its greatest incidence in children under 2 years of age.children under 2 years of age.

the disease is a serious problem with a high the disease is a serious problem with a high mortality (10%) with malnutrition being an mortality (10%) with malnutrition being an important factorimportant factor in developing countries in developing countries

In general measles mortality is highest in In general measles mortality is highest in children < 2 years and in adultschildren < 2 years and in adults

Temporal patternTemporal pattern Peak in late Peak in late winter–springwinter–spring

CommunicabilityCommunicability 4 days before 4 days before to 4 days after rash onset.to 4 days after rash onset.

Strategy for sustainable Strategy for sustainable measles mortality reductionmeasles mortality reduction

1. Strong routine immunization 1. Strong routine immunization > > 90%90%• Reaching Every District StrategyReaching Every District Strategy

3. Surveillance3. Surveillance

2. Provide second opportunity for 2. Provide second opportunity for measles immunizationmeasles immunization• One time onlyOne time only “catch-up” campaign ( < 15 ) “catch-up” campaign ( < 15 )• “ “Follow-up” campaigns every 3-4 years ( < 5 ) Follow-up” campaigns every 3-4 years ( < 5 ) • Routine scheduled second dose / opportunity Routine scheduled second dose / opportunity

4. Improved case management4. Improved case management

Palestine

Bahrain

Measles Campaigns in EMRO through 2005

Preschool and school age (13)School age (5)Preschool age (1)

Not done (1)

Ongoing (2)

1963 Live attenuated and killed vaccines

1965 Live further attenuated vaccine

1967 Killed vaccine withdrawn

1968 Live further attenuated vaccine

(Edmonston-Enders strain)

1971 Licensure of combined measles-

mumps-rubella vaccine

1989 Two dose schedule

2005 Licensure of MMRV

Measles VaccinesMeasles Vaccines

Measles VaccineMeasles Vaccine CompositionComposition Live virusLive virus EfficacyEfficacy 95% (range, 90%-98%)95% (range, 90%-98%) Duration ofDuration of

ImmunityImmunity LifelongLifelong ScheduleSchedule 2 doses2 doses Should be administered with mumps and rubella as Should be administered with mumps and rubella as

MMR MMR

The seroconversion rate is 95% and the The seroconversion rate is 95% and the immunity lasts for at least 10 years or immunity lasts for at least 10 years or more, possibly lifelongmore, possibly lifelong

MMRV (ProQuad)MMRV (ProQuad)

Combination measles, mumps, rubella Combination measles, mumps, rubella and varicella vaccineand varicella vaccine

Approved children 12 months through 12 Approved children 12 months through 12 years of age (up to age 13 years)years of age (up to age 13 years)

Titer of varicella vaccine virus in MMRV Titer of varicella vaccine virus in MMRV is more than 7 times higher than is more than 7 times higher than standard varicella vaccinestandard varicella vaccine

MMR Vaccine FailureMMR Vaccine Failure

Measles, mumps, or rubella disease (or lack of Measles, mumps, or rubella disease (or lack of immunity) in a previously vaccinated personimmunity) in a previously vaccinated person

2%-5% of recipients do not respond to the first 2%-5% of recipients do not respond to the first dosedose

Caused by antibody, damaged vaccine, record Caused by antibody, damaged vaccine, record errorserrors

Most persons with vaccine failure will respond Most persons with vaccine failure will respond to second doseto second dose

Measles (MMR) Vaccine IndicationsMeasles (MMR) Vaccine Indications

All infants All infants >>12 months of age12 months of age Susceptible adolescents and adults Susceptible adolescents and adults

without documented evidence of immunitywithout documented evidence of immunity

Measles Mumps Rubella VaccineMeasles Mumps Rubella Vaccine

12 months is the recommended and 12 months is the recommended and minimum ageminimum age

MMR given before 12 months should not MMR given before 12 months should not be counted as a valid dosebe counted as a valid dose

Revaccinate at Revaccinate at >>12 months of age12 months of age

Second Dose of Measles VaccineSecond Dose of Measles Vaccine

Intended to produce measles immunity in Intended to produce measles immunity in persons who failed to respond to the first persons who failed to respond to the first dose (primary vaccine failure)dose (primary vaccine failure)

May boost antibody titers in some personsMay boost antibody titers in some persons

Second Dose RecommendationSecond Dose Recommendation

First dose of MMR at 12-15 monthsFirst dose of MMR at 12-15 months Second dose of MMR at 4-6 yearsSecond dose of MMR at 4-6 years Second dose may be given any time Second dose may be given any time >>4 4

weeks after the first doseweeks after the first dose

MMR Adverse ReactionsMMR Adverse Reactions FeverFever 5%-15%5%-15%

RashRash 5%5%

Joint symptomsJoint symptoms 25%25% ThrombocytopeniaThrombocytopenia <1/30,000 <1/30,000 dosesdoses

ParotitisParotitis rarerare

DeafnessDeafness rarerare EncephalopathyEncephalopathy <1/1,000,000 <1/1,000,000 dosesdoses

MMR Vaccine and AutismMMR Vaccine and Autism

Measles vaccine connection first suggested Measles vaccine connection first suggested by British gastroenterologistby British gastroenterologist

Diagnosis of autism often made in second Diagnosis of autism often made in second year of lifeyear of life

Multiple studies have shown no associationMultiple studies have shown no association

MMR Vaccine and AutismMMR Vaccine and Autism

““The evidence favors a rejection of a causal The evidence favors a rejection of a causal relationship at the population level between relationship at the population level between MMR vaccine and autism spectrum MMR vaccine and autism spectrum disorders (ASD).”disorders (ASD).”

- Institute of Medicine, April 2001- Institute of Medicine, April 2001

MMR VaccineMMR VaccineContraindications and PrecautionsContraindications and Precautions

Severe allergic reaction to vaccine Severe allergic reaction to vaccine component or following prior dosecomponent or following prior dose

PregnancyPregnancy ImmunosuppressionImmunosuppression Moderate or severe acute illnessModerate or severe acute illness Recent blood productRecent blood product

The use of live-attenuated vaccine for post-The use of live-attenuated vaccine for post-exposure prophylaxis is contraindicated.exposure prophylaxis is contraindicated.