Epidemiology of measles in vaccinated people, Spain 2003-2014.
BACKGROUND
During the final phase of measles elimination rigorous investigation of each individual case becomes fundamental to confirm or discard cases, particularly among vaccinated people, since they experience a milder disease, and laboratory diagnosis is more complex. Our study focused in the epidemiology of measles in vaccinated people.


METHODS
Longitudinal study on measles cases in two dose vaccinated people in Spain from 2003 to 2014.


RESULTS
We confirmed 138 measles cases (90 of them, laboratory confirmed) in people with two doses of vaccine. The median of time from last vaccination to rash onset showed a lineal trend (P<.001), in parallel with the number of doses of vaccine received (0, 1, 2 doses). Among confirmed cases, the hospitalization risk decreased inversely proportional to the number of administered vaccine doses (linear trend, P<.001). Only in 23.9% of confirmed cases and 50% of discarded cases the guidelines about sample taking were fulfilled. 50% of samples in two dose vaccinated people were taken without fulfilling time delay criteria. 16.7% (36/215) of discarded cases with a negative IgM result did correspond to samples taken early (first 72h after rash) and could represent false negatives.


CONCLUSIONS
Our results highlight the importance of fulfilling properly the guidelines for laboratory diagnosis in order to confirm or discard every measles case, especially in two dose vaccinated people. When a negative IgM result is obtained in early samples a new IgM test should be practiced, as well as a PCR test, in order to avoid infra-detection of cases.
Unidad de Medicina Preventiva y Salud Pública, Hospital Universitario Fundación Alcorcón, Alcorcón, Madrid, España. Electronic address: carlosriscorisco@yahoo.es.
Carlos
C
Risco-Risco
Centro Nacional de Epidemiología, CIBERESP, Instituto de Salud Carlos III, Madrid, España.
Josefa
J
Masa-Calles
Centro Nacional de Epidemiología, CIBERESP, Instituto de Salud Carlos III, Madrid, España.
Noemí
N
López-Perea
Laboratorio de Referencia e Investigación en Enfermedades Víricas Inmunoprevenibles, Unidad de Aislamiento y Detección de Virus, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, Madrid, España.
Juan Emilio
JE
Echevarría
Unidad de Medicina Preventiva y Salud Pública, Hospital Universitario Fundación Alcorcón, Alcorcón, Madrid, España.
Gil
G
Rodríguez-Caravaca
D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D006801:Humans; D008137:Longitudinal Studies; D008457:Measles / Q000453:epidemiology* / Q000517:prevention & control*; D008458:Measles Vaccine; D013030:Spain / Q000453:epidemiology; D013997:Time Factors; D055815:Young Adult
D008458:Measles Vaccine
Diagnosis; Diagnóstico; Eliminación; Elimination; Evanescencia; Fallo vacunal secundario; Measles; Sarampión; Secondary vaccine failure; Surveillance; Vigilancia; Waning immunity