Confounders are always a problem.
Brunskill
A J
AJ
D002675:Child, Preschool; D015986:Confounding Factors, Epidemiologic; D006801:Humans; D008457:Measles / Q000453:epidemiology / Q000401:mortality / Q000517:prevention & control; D008458:Measles Vaccine / Q000276:immunology*
D008458:Measles Vaccine