Seroprevalence of Measles and Rubella Virus Immunity among US Army Recruits

Background:
Recruit seroprevalence data provide insight of measles and rubella immunity among young adults in the US. National immunization surveillance data from 2007 estimated high levels of measles-mumps-rubella (MMR) vaccine coverage among adolescents (88.9% for two doses). The US Army performs serologic screening of recruits for pre-existing immunity to measles and rubella; those who are seronegative are vaccinated with two doses of MMR vaccine. Mumps screening is not performed because previous studies have shown a high concordance for mumps immunity with measles and rubella immunity.

Objectives:
Describe seroprevalence of measles and rubella immunity among Army recruits and compare seroprevalence based on recruit demographics.

Methods:
Seroprevalence data were collected for Army recruits from April 2006 to June 2007 and linked to demographic data from the Defense Medical Surveillance System. Immunity was determined by serum antibody titers, yes (positive) or no (negative or equivocal). Independent variables included age, race, gender, basic training site, marriage status, military rank, and home state. Analysis was accomplished using multivariable categorical logistic regression.

Results:
Sample included 114,684 records. Mean age was 21.4 ±4.8, most recruits were male (81.9%), white (71.2%), and from states in the south region of the US (42.5%). Sample mean seroprevalence for measles and rubella immunity was 73.3%. Female recruits were more likely to be seropositive than male recruits (OR 1.3, p-value <.0001). Recruits at Fort Jackson, SC, were two times more likely to be seropositive than recruits at Fort Leonard Wood, MO, (OR 2.0, p-value <.0001). Older recruits (23–42 years) were slightly less likely (OR 0.84, p-value <.0001) to be seropositive compared to younger recruits.

Conclusions:
Seroprevalence among Army recruits was lower than the CDC's National Immunization Survey MMR vaccination coverage estimated for adolescents. Assessment of immunity leads to a reduction in unnecessary immunizations among recruits and provides important vaccination coverage information.