Background: Measles, mumps, rubella, and varicella (MMRV) were common childhood diseases in the United States prior to the introduction of their respective vaccines. Measles was declared eliminated in the United States in 2000. However, 628 cases were reported in 2014, the majority of which have been linked to international travel. The study team set out to investigate the seroprevalence of MMRV in our local population to determine whether such a process can lead to meaningful recommendations for assessing travelers at risk.
Methods: We conducted a cross-sectional seroprevalence study using a quota sampling method. A total of 460 leftover serum samples were collected from individuals born prior to 1996, who live in the Lehigh Valley region of southeast Pennsylvania. The samples were allocated to five birth-year cohorts, and the seroprevalence of each cohort to MMRV was compared. Additionally, overall seroprevalence of each disease was compared with data from prior national studies. Gender differences within each birth cohort were also assessed.
Results: The overall seroprevalence values of measles, mumps, rubella, and varicella were 85.8, 82.8, 96.6, and 97.4%, respectively. There were significant associations between seroprevalence and birth cohort for measles (p = 0.01) as well as mumps (p = 0.037). The overall seroprevalence for our study sample was significantly different from the national seroprevalence results of measles, mumps, and rubella.
Conclusions: Our study showed dramatically lower immunity rates for measles and mumps than those shown by prior national seroprevalence studies. The rates in many of the later birth cohorts born after 1966 were significantly lower than the rates reported as necessary to sustain herd immunity. Given that patients' immunization records are not always available or complete, collecting local seroprevalence data may be necessary to more accurately recommend antibody testing and vaccination during pre-travel assessments.
© 2015 International Society of Travel Medicine.