Emergence of Attenuated Measles Illness among IgG-positive/IgM-negative Measles Cases: Victoria, Australia, 2008-2017

Abstract

Background: Waning measles immunity among vaccinated individuals may result in an attenuated illness. This study compares the epidemiological, clinical, and laboratory profile of measles cases with waning immunity with other measles cases. Methods: Polymerase chain reaction-positive (+) measles cases notified to Victoria's Department of Health and Human Services from 2008 to 2017 with immunoglobulin (Ig) M and IgG tested at diagnosis were classified according to serology at diagnosis: IgG negative (-) (nonimmune), IgM+/IgG+ (indeterminate), or IgM-/IgG+ (waning immunity). Results: Between 2008 and 2017, 297 measles cases were notified, of whom 190 (64%) were included; 151 of 190 (79%) were n..