Measles, Rubella and Varicella IgG Seroprevalence in a Large Refugee Cohort in Germany in 2015: A Cross-Sectional Study

INTRODUCTION: The current extent of migration to the European continent is associated with exceptional humanitarian challenges. In 2015, Western Europe faced an enormous immigration of refugees with largely unknown protection status against communicable diseases. To adapt vaccination strategies, we aimed at assessing seroprevalences against three of the most relevant vaccine preventable diseases (VPD) in a large representative cohort. METHODS: IgG seroprevalences for rubella, varicella (n = 554) and measles (n = 552) were analyzed in inhabitants of a Northern German refugee camp in the summer of 2015. RESULTS: Of the refugees, 77.9% were male (mean age 27.4 years for male and 26.8 years for female migrants). Most refugees came from the Eastern Mediterranean region (83.4%), followed by immigrants from Eastern Europe (7.4%), Africa (4.6%), or other regions (4.5%). The vast majority of migrants were protected against the three VPD: overall IgG seropositivity was 88.5% for measles, 77.9% for rubella and 95.9% for varicella. However, seroprevalences showed age- and origin-dependent differences. Varicella immunity, for example, was lowest in the youngest age group of both genders (10.1% of male/4.5% of female seronegative refugees <18 years vs. 100% seropositivity in men and women >49 years of age), and Sudanese migrants displayed particularly low rates of protection against varicella. CONCLUSION: In accordance with previous studies, our analyses show an overall satisfactory seropositivity against measles, rubella, and varicella in refugees entering Europe during the current exodus. However, this rate is not sufficient for preventing transmission. For example, the rate of 12.9–17.9% female refugees at reproductive age unprotected against measles and the low protection levels against varicella in minors observed in our cohort emphasizes the need for stringent vaccination strategies in refugees coming to Europe during the current crisis.