Epidemiology of Measles Prof. Ashry Gad Mohamed Prof. of Epidemiology

 Highly contagious viral illness  First described in 7th century  Near universal infection of childhood in prevaccination era  Common and often fatal in developing areas

No second opportunity for measles immunization ( 45 ) 94 % of all measles deaths in 2000 Leading killer of children We know WHERE...

Cases 2005 . An estimated people, the majority of them children, died from measles in  From 2000 to 2005, more than 360 million children globally received measles vaccine. 

Global Progress Measles Mortality Reduction by 50% by 2005 (compared to 1999 : 875,000 deaths) Estimated Measles Mortality by Year

Deaths from Measles  Africa [ ]  Americas <1 000 [-]  Eastern Mediterranean [ ]  European <1 000 [-]  South-East Asia [ ]  Western Pacific 5000 [ ]  TOTAL [ ]

Measles Mortality Reduction in EMRO Region, EMRO

Libya Egypt Sudan Morocco Tunisia Somalia Saudi Arabia Yemen Oman Djibouti Pakistan Afghanistan Iran Iraq Syria Jordan Lebanon Palestine Qatar UAEBahrain Kuwait

Percent reduction in estimated measles deaths by WHO region between 1999 and 2002

Measles Case Counts and Coverage Saudi Arabia

 There was a marked reduction in the epidemic peak from 500/ in the 1970s to < 80/ in the 1990s.  Incidence among children 6–8 months of age fell from > 400/ before the implementation of the new policy to 200/ before the implementation of the new policy to 400/ before the implementation of the new policy to 200/ before the implementation of the new policy to <100/ in  cases

Measles Pathogenesis  Respiratory transmission of virus  Replication in nasopharynx and regional lymph nodes  Primary viremia 2-3 days after exposure  Secondary viremia 5-7 days after exposure with spread to tissues

Measles Clinical Features  Incubation period days  Stepwise increase in fever to 103°F or higher  Cough, coryza, conjunctivitis, malaise, sneezing, rhinitis, congestion  Koplik 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 Features  2-4 days after prodrome, 14 days after exposure  Maculopapular, becomes confluent  Begins on face and head  Persists 5-6 days  Fades in order of appearance Rash

Child has a rash caused by measles

Measles rash covering child's arms and stomach

ConditionDiarrhea Otitis media PneumoniaEncephalitisHospitalizationDeath Percent reported Measles Complications Based on surveillance data

Measles Complications by Age Group

Measles Clinical Case Definition  Generalized rash lasting >3 days, and  Temperature 101°F (>38.3°C), and  Cough or coryza or conjunctivitis

Measles Laboratory Diagnosis  Isolation of measles virus from a clinical specimen (e.g., nasopharynx, urine)  Significant rise in measles IgG by any standard serologic assay (e.g., EIA, HA)  Positive serologic test for measles IgM antibody

Measles Virus  Paramyxovirus (RNA)  One antigenic type  Rapidly inactivated by heat and light

Reservoir  Human Incubation period. Clinical case Clinical case  No animal reservoir

Transmission  The virus spreads by the respiratory route via aerosol droplets and respiratory secretions which can remain infectious for several hours.  The infection is acquired through the upper respiratory tract or conjunctiva

 In the pre-vaccination era, the maximum incidence was seen in children aged years. By the age of 20, approximately 99% of subjects have been exposed to the virus.  With the introduction of vaccine, measles infection has shifted to the teens in countries with an efficient programme.

 In contrast, in third world countries, measles infection has its greatest incidence in children under 2 years of age.  the disease is a serious problem with a high mortality (10%) with malnutrition being an important factor in developing countries  In general measles mortality is highest in children < 2 years and in adults

 Temporal pattern Peak in late winter–spring  Communicability 4 days before to 4 days after rash onset.

Strategy for sustainable measles mortality reduction 1. Strong routine immunization > 90% Reaching Every District Strategy Reaching Every District Strategy 3. Surveillance 2. Provide second opportunity for measles immunization One time only “catch-up” campaign ( < 15 ) One time only “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 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)

1963Live attenuated and killed vaccines 1965Live further attenuated vaccine 1967Killed vaccine withdrawn 1968Live further attenuated vaccine (Edmonston-Enders strain) 1971Licensure of combined measles- mumps-rubella vaccine 1989Two dose schedule 2005Licensure of MMRV Measles Vaccines

Measles Vaccine  CompositionLive virus  Efficacy95% (range, 90%-98%)  Duration of ImmunityLifelong  Schedule2 doses  Should be administered with mumps and rubella as MMR  The seroconversion rate is 95% and the immunity lasts for at least 10 years or more, possibly lifelong

MMRV (ProQuad)  Combination measles, mumps, rubella and varicella vaccine  Approved children 12 months through 12 years of age (up to age 13 years)  Titer of varicella vaccine virus in MMRV is more than 7 times higher than standard varicella vaccine

MMR Vaccine Failure  Measles, mumps, or rubella disease (or lack of immunity) in a previously vaccinated person  2%-5% of recipients do not respond to the first dose  Caused by antibody, damaged vaccine, record errors  Most persons with vaccine failure will respond to second dose

Measles (MMR) Vaccine Indications  All infants >12 months of age  Susceptible adolescents and adults without documented evidence of immunity

Measles Mumps Rubella Vaccine  12 months is the recommended and minimum age  MMR given before 12 months should not be counted as a valid dose  Revaccinate at >12 months of age

Second Dose of Measles Vaccine  Intended to produce measles immunity in persons who failed to respond to the first dose (primary vaccine failure)  May boost antibody titers in some persons

Second Dose Recommendation  First dose of MMR at months  Second dose of MMR at 4-6 years  Second dose may be given any time >4 weeks after the first dose

MMR Adverse Reactions  Fever5%-15%  Rash5%  Joint symptoms 25%  Thrombocytopenia<1/30,000 doses  Parotitis rare  Deafness rare  Encephalopathy <1/1,000,000 doses

MMR Vaccine and Autism  Measles vaccine connection first suggested by British gastroenterologist  Diagnosis of autism often made in second year of life  Multiple studies have shown no association

MMR Vaccine and Autism “The evidence favors a rejection of a causal relationship at the population level between MMR vaccine and autism spectrum disorders (ASD).” “The evidence favors a rejection of a causal relationship at the population level between MMR vaccine and autism spectrum disorders (ASD).” - Institute of Medicine, April Institute of Medicine, April 2001

MMR Vaccine Contraindications and Precautions  Severe allergic reaction to vaccine component or following prior dose  Pregnancy  Immunosuppression  Moderate or severe acute illness  Recent blood product

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