It has been noted on occasion that chickenpox and measles may occur together or one may precede the other by a few days. Artenstein and Weinstein1 estimated that about 15 such cases occurred in the state of Massachusetts in 1961. On the other hand, Merigan et al2 noted the occurrence of both diseases within a few weeks in seven of 18 children who were admitted to a youth guidance center. It is probable that double infections are more likely to occur when the patients are young and when opportunity for intense exposure to both agents is present.
The most remarkable thing about these cases of double infection is the finding that the first infection may diminish the severity of the rash of the second infection. Evidence for interference with measles rash by chickenpox is based on the finding of clear zones of normal skin encircling healing chickenpox crusts
Knight V. Inhibition of Chickenpox Lesions by Measles and Measles Rash by Chickenpox. JAMA. 1973;223(10):1154-1155. doi:10.1001/jama.1973.03220100048013