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Measles Epidemiology United States, 2006. Jane Seward, MBBS, MPH Acting Deputy Director, Division Viral Diseases Centers for Disease Control and Prevention. FDA BPAC Meeting Bethesda, August 16 th , 2007. Measles. Highly contagious viral illness
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Measles EpidemiologyUnited States, 2006 Jane Seward, MBBS, MPH Acting Deputy Director, Division Viral Diseases Centers for Disease Control and Prevention FDA BPAC Meeting Bethesda, August 16th, 2007
Measles • Highly contagious viral illness • Near universal childhood infection in the pre-vaccine era • Morbidity and mortality 1950s, United States • 450 deaths annually • 48,000 hospitalizations • 4,000 cases encephalitis
Measles Prevention • Live, attenuated measles vaccine licensed 1963 • Almost all administered as MMR vaccine • Efficacy • One dose ≥ 12 months: 95% • Two doses at least 4 weeks apart ≥ 12 months: 99% • Schedule: 2 doses • Children 4-6 years (school students) • College students • Health care workers • International travelers
Maximize population immunity to measles • Deliver the first dose on time • Increase second dose coverage in school children • Vaccinate high risk adults • Assure adequate surveillance • Respondrapidly to outbreaks • Work to improve global control Strategies to Control and Eliminate Measles, US
Reported Measles Cases by Year, United States, 1950-2006 Second dose strategy and school laws Vaccine licensed School immunization laws started in all states Improved first dose preschool coverage
Reported Measles IncidenceUnited States, 1992-2006* Measles elimination declared 1 case/million *provisional 2006 data
Age Distribution of Measles CasesUS, 2001-2006 * Provisional
Vaccination Status Measles CasesUS, 2001-2006 * From NNDSS
Measles Genotypes and Measles Cases USA: 1980-2005 30,000 25,000 20,000 Interruption in transmission 15,000 Measles Cases 10,000 5,000 0 80 81 82 83 84 85 86 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 87 G1 D3 A, C2, B2, B3, D2, D4, D3, D5, D6, D7, D8, G2, H1, H2 Viral Genotypes (2 strains in 1983) (30 isolations) (>100 isolations)
Imported Measles Cases1996-2005* Total Cases Imported - 348 Japan - 50 cases China - 36 cases Germany - 26 cases India - 23 cases Philippines - 19 cases Italy - 17 cases Pakistan - 15 cases Greece, United Kingdom – 11 cases each 54 other countries – 140 cases *2005 provisional data through Oct 29
Measles in the U.S.—2006* • 55 cases reported by 16 states • States reporting largest number of cases: MA (18), NY (10), CA (6) & FL (4) • 52 cases (95%) were imported-associated cases: • 31 imports • 20 epi-linked to imported cases • 1 virus only case • 3 cases were unknown source cases *CDC data, unpublished
Source Countries for 2006 Imported Measles Cases (N=31) India 6 Ukraine 6 China 5 U.K. 3 Pakistan 2 Australia 2 Italy 1 Hong Kong 1 Thailand 1 Kenya 1 Ethiopia 1 Uganda 1 Yemen 1
2006 Measles Outbreaks • 4 outbreaks: • MA (18 cases) resulting from single import from India -- Office Building(s) • FL (3 cases) among cruise ship employees, source Ukraine • NYS (3 cases) among Immigrants living in a Yemen community • CA (1 case) WA (1 case) MO (1 case) - 3 mothers exposed in China during adoptions
Cases in US in 2006 with genotype associated with case(s) or outbreaks 1 case : H1 [Hong Kong] 1 case: D6 [Ukraine] 1 case: B3 [inter’l travel, UK] Oregon Indiana New York City 1 case: D8 [inter’l travel Australia] Boston 17 cases: D8 [India] 2 cases: B3 [travel: Disneyworld] 1 case: D8 [India] 3 cases: B3 [Yemen] 1 case: D4 [Pakistan] 1 case: D6 [Ukraine] 1 case: H1 [China] 1 case: B3 [UK]
Cases in US in 2005 with genotype associated with case(s) or outbreaks 1 case: D4 [inter’l meeting, France] 2 cases: D4 [inter’l travel, Germany] 34 case outbreak: D4 [Romania] & 1 case: D4 [Romania] Washington 1 case: D4 [Yemen] Wisconsin 2 Indiana Illinois 1case:D8 [India] Michigan New York 2 3 1 case: D9 Indonesia] & 1 case: D8 [India] New York City 1 33 1 New Jersey 1 3 1 case: B3 [Kenya] Arizona Texas 1 case: D6 [Armenia] 3 cases: B3 [inter’l travel, Mexico]
Extremely low incidence • Majority of cases are internationally imported or import associated • Surveillance system is adequate • Population immunity is very high • No endemic strain of measles virus Evidence for Elimination of Endemic Measles in the U.S.
Adequate Surveillance to Detect Endemic Measles • Consistent detection of imported measles cases • Detection of isolated cases and small outbreaks • High level of investigative effort for measles • Molecular typing consistent with elimination of indigenous genotype of measles virus
First dose coverage > 90% since 1996 for 19-35 month-old children • First dose coverage > 97% for school-age children • Second dose required for 82% of school children as of 2001 • Seroprevalence 1999-2004 shows 96% immunity (EIA) ages 6-49 years High Population Immunity
Prevalence of Measles AntibodiesU.S Population, 1988-1994 93% ≥ 6 years Born < 1957 99% Born >= 1957 87% Born 1967-76 81% Hutchins SS et al, JID 2004
Duration of Vaccine Induced Immunity? • US has used measles vaccine since 1963 • Some vaccine recipients received measles vaccine 40 years ago • Younger cohorts are not being exposed to wild measles virus • Important to monitor population immunity including whether immunity remains above the protective level
Persistence of Measles Antibodies After 2 Doses of Measles Vaccine in a Postelimination Environment LeBaron CW, Beeler J, Sullivan BJ et al. Arch Pediatr Adolesc Med. 2007;161:294-301
Projected Measles Antibody Levels following MMR2 Vaccination at Kindergarten Age A, Titers in the kindergarten group B, Percentage potentially susceptible in the kindergarten group.
Persistence of Vaccine-Induced Measles Antibody • Small long term follow up study of persons from vaccine trial in 1971 • Participants 26-33 years after last measles vaccine dose • No known exposures to measles • All 56 participants had PRN antibody ≥ 1:8 • 9% had PRN titer ≤ 120 (not considered protective) • Cellular immunity? Dine MS, Hutchins SS et al JID 2004
Conclusions • Measles no longer endemically transmitted in U.S. • Almost 100% cases are import associated • Importations continue to challenge population immunity • Extremely limited spread from importations due to high population immunity • No indication of immunity waning to “susceptibility” from epidemiological data • Continue long term monitoring of vaccine-induced immunity