A Limited Measles Outbreak in U.S.-Born Children Living in a Military Community in Germany after Vaccine Refusal and Other Vaccination Delays

Military Medicine, Aug 2008 by Mancuso, James D

ABSTRACT This report summarizes an outbreak of measles among five unvaccinated children living in a U.S. military community in Wiesbaden, Germany, in March to April of 2004. The index case was a 3-year-old whose parents' refusal to have their child vaccinated with measles-containing vaccine had been documented many times. Four other cases developed from contact with the index case. The two older children had multiple missed opportunities for vaccination documented. Record review revealed that only 71% of 19- to 35-month olds in the community had been vaccinated with measles-containing vaccine before the outbreak, creating a "pocket of susceptibility." Children of travelers, expatriates, and military service members are at increased risk from vaccine-preventable diseases. Vaccine refusal is increasingly common, resulting in pockets of susceptibility to vaccine-preventable diseases, and increasing the risk of outbreaks. Missed opportunities and other delays in vaccination can also contribute to these pockets of susceptibility.

INTRODUCTION

Measles is a highly infectious, acute viral illness, characterized by fever, rash, cough, conjunctivitis, and coryza, and can lead to pneumonia and death. With the advent of the vaccine era, the incidence of measles in the United States decreased from ~500,000 per year to 66 in 2005.1 Although measles is a vaccine-preventable disease, outbreaks can occur despite high levels of vaccination in a community due to "pockets of susceptibility."2 An outbreak in 2005 was associated with parental refusal to vaccinate leading to an unvaccinated child acquiring measles infection outside the United States (in Romania), resulting in 34 cases. Other outbreaks have been associated with religious groups and other groups opposed to vaccination.3 Since measles is no longer endemic in the United States, all cases are associated with overseas travel or other importation.1,4

This report summarizes an outbreak of five cases of measles in a U.S. military community in Wiesbaden, Germany, during March to April 2004. The outbreak investigation was aimed at understanding the factors leading to pockets of measles susceptibility in the population. A better understanding of these factors will enable more effective prevention efforts aimed at eliminating or reducing the magnitude of these outbreaks.

METHODS

The period of the outbreak was defined as extending from one incubation period (14 days) before the onset of rash in the index patient until one incubation period after the last onset of rash in a patient, or March 1 to April 28, 2004. A clinical case of measles was defined as an illness characterized by all of the following: (1) a generalized maculopapular rash lasting at least 3 days; (2) a temperature of at least 101°F (38.3°C); and (3) cough, coryza, or conjunctivitis.5 A case was considered confirmed if it was either: (1) laboratory-confirmed, or (2) epidemiologically linked to one of the confirmed cases. A patient was considered to have laboratory-confirmed measles if a sample of the patient's serum tested positive for anti-measles immunoglobulin M (IgM) with the use of the Measles IgM EIA Capture Assay at the Wiesbaden Public Health Laboratory or Landstuhl Regional Medical Center Laboratory,6 or if a nasopharyngeal or urine specimen tested positive for measles virus by polymerase chain reaction or viral culture, according to WHO guidance.7,8 A patient was considered to have been infectious from 4 days before and 4 days after onset of rash.9

We examined measles vaccination coverage in the community at the time of the outbreak using health care provider vaccination records according to the standards of the Centers for Disease Control and Prevention's National Immunization Survey (NIS).10,11 The purpose of this examination was to assess susceptibility in the community and to target efforts aimed at increasing vaccination coverage of those at highest risk for the disease and subsequent complications. The 19- to 35-month-old population was chosen as a sentinel population to assess measles susceptibility since the index case was in this group, they were less likely to have vaccination assessed previously (i.e., for school requirements), and for comparability to the NIS.

The Wiesbaden military community consisted of 7,974 enrolled beneficiaries, including 2,903 active duty service members; 3,692 spouses and children; and 1,379 other affiliated beneficiaries (mostly retirees and their families).12 Of note, 1,014 children ages 5 and under were enrolled at the time of the outbreak, and 230 of these were children ages 19 to 35 months; 158 (69%) records were actually found in the clinic. This compares favorably with the provider vaccination record review response found in the NIS of 64%, and better than the NIS overall response of 41% when including parent response.13

RESULTS

The outbreak curve is shown by date of onset of rash in Figure 1. A total of five cases of measles were identified. Four were laboratory-confirmed: three by serum IgM, and one by viral culture; one was epidemiologically linked to a laboratory-confirmed case (a sibling). One case, a 22-month-old male child, was hospitalized for pneumonia but recovered without sequelae. The index case was immediately isolated on initial presentation to the clinic and a contact investigation was simultaneously begun. Medical and public healtii staff in both the U.S. and German communities were notified, and active surveillance and case finding were initiated. The case was presumed to have been exposed during a trip to a vacation resort in Bavaria. Since the child did not attend day care or other institutional settings, had no siblings, and had no other known contact with susceptibles, the risk for secondary cases was felt to be low. Thus, mass vaccination was not recommended at that time. However, 2 weeks later, three secondary cases developed due to incidental exposure to the index case. This had occurred in a play area at the local tax assistance center on the day before rash onset in the index case, but this information had not been elicited during the initial contact investigation. These cases were also isolated; their contacts were vaccinated and selectively quarantined.