Identification of Patients

During the outbreak period, 66 persons who were suspected to have measles were identified, of whom 32 (48 percent) were determined not to have measles because they either had a negative laboratory test for acute measles infection or were not epidemiologically linked to a patient with laboratory-confirmed measles. Of the remaining 34 persons, 14 (41 percent) had laboratory-confirmed measles and 20 (59 percent) were epidemiologically linked to a laboratory-confirmed case. All epidemiologically linked patients had the characteristic maculopapular rash and at least two of the following symptoms: fever, cough, coryza, conjunctivitis, otitis media, or diarrhea. We obtained specimens for viral isolation and molecular characterization from 14 patients, and measles virus was isolated in 6. All molecular sequences from the outbreak were identical, and all were members of genotype D4, which is endemic in Romania, as well as in other areas of Eastern Europe, the Indian subcontinent, the Middle East, and Eastern Africa.18 A representative sequence from the outbreak, MVs/Indiana.USA/23.05 [D4] (GenBank accession number DQ355989), was most closely related to sequences obtained from contemporary measles viruses isolated from patients in Romania.

Demographic Characteristics and Vaccination Status of Patients

Figure 1. Figure 1. Distribution of Patients According to Age and Vaccination Status, Indiana, May to June 2005.

Of the 34 patients, 33 (97 percent) were self-declared non-Hispanic white, 33 (97 percent) were members of the church that held the gathering, 28 (82 percent) were 5 to 19 years of age (of these, 20 [71 percent] were home-schooled), and 32 (94 percent) lacked evidence of measles vaccination (Figure 1). Of the 32 patients without evidence of vaccination, 2 were ineligible for routine vaccination (1 was born before 1957 and 1 was less than 12 months of age) and 2 had a vaccination status that could not be determined.

Vaccine Failure

Vaccine failure, which was defined as confirmed measles disease in a person who had been documented to have previously received measles vaccine, occurred in two patients. A 16-year-old student attended the church gathering and 14 days later had a morbilliform rash after having had prodromal fever, cough, and coryza. She was epidemiologically linked to a patient with laboratory-confirmed measles, but no specimen was obtained from her for laboratory confirmation. She had received a dose of measles vaccine at 13 months of age and a dose at 4.5 years of age, which are within the age ranges recommended by the ACIP for school-age children.20 Neither this patient nor anyone else at the gathering had been offered postexposure prophylaxis, since the exposure to measles had not been recognized until two weeks after the gathering, which was beyond the period of prophylaxis effectiveness.20 The other patient with vaccine failure was a 34-year-old hospital phlebotomist who was hospitalized for severe measles. Serum drawn four days after the onset of rash was positive for anti-measles IgM and IgG. Her direct source of exposure could not be identified, but she worked at the hospital where two of the patients with measles had been treated. She had received one dose of measles vaccine at 12 months of age but did not have documentation of a second dose and had not been tested for serologic evidence of immunity on employment. The ACIP recommends either proof of measles vaccination with two doses or evidence of immunity for health care workers.20

Complications

Three patients (9 percent) were hospitalized — a 45-year-old man and a 6-year-old girl required intravenous rehydration, and the hospital phlebotomist, who had no coexisting conditions but did have a history of smoking, required six days of ventilator support for pneumonia complicated by the acute respiratory distress syndrome. Sixteen patients (47 percent) had diarrhea, and two (6 percent) had otitis media. No deaths occurred.

Patterns of Transmission

Figure 2. Figure 2. Patients with Measles According to the Day of Onset of Rash, Indiana, May to June 2005. The first generation of spread consisted of 19 patients who were exposed to the index patient (18 at the gathering and 1 during a visit with a neighbor). The second generation consisted of 12 patients who had household contact with a person infected by the index patient. The third generation consisted of two patients, one with household exposure and one hospital worker who had an unknown exposure.

Table 1. Table 1. Characteristics of All Households in Which a Person with Confirmed Measles Resided.

Three generations of the spread of measles occurred during a six-week period (Figure 2). Thirty-two cases (94 percent) occurred in Indiana Counties A and B, one in Indiana County C, and one in Illinois. An estimated 500 persons had attended the church gathering; approximately 50 lacked evidence of measles immunity, and of these 50, 16 (32 percent) acquired measles at the gathering. Of the estimated 450 other persons, 2 (<1 percent) acquired measles at the gathering (an adult born before 1957 and the student described above who had received two documented doses of measles vaccine). Of the 34 patients, 19 (56 percent) were infected directly by the index patient (18 at the gathering and 1 during a visit with a neighbor), and 13 (38 percent) were infected by household contact with a person infected by the index patient. Although 20 patients were infectious and interacted with the surrounding community before public health authorities were notified and instituted measures to contain the disease, no known transmission occurred in community or health care settings, with the exception of the hospital phlebotomist. Four households accounted for 24 of the 34 patients (71 percent) (Table 1). Of 69 persons in the 11 affected households, 56 (81 percent) lacked evidence of immunity according to the ACIP standards. Of these, 32 (57 percent) acquired measles; 18 of the remaining 24 reported a history of measles disease or vaccination but lacked the documentation needed to meet ACIP criteria for immunity, 4 met none of the criteria for immunity, and 2 had unknown vaccination or disease status.

Rates of Vaccination Coverage in the Community

The National Immunization Survey estimated that the 2004 rate of first doses of measles-vaccination coverage among children 19 to 35 months of age in Indiana was 92 percent (95 percent confidence interval, 88.1 to 95.9 percent). The lowest estimate in the previous 10 years was 86 percent (95 percent confidence interval, 82 to 90 percent) for 1996.22 The rate of two-dose measles-vaccination coverage in Indiana for the 2004 to 2005 school survey was 98 percent of kindergarteners (78,637 of 80,495) and 98 percent of sixth graders (83,252 of 84,523); the proportion of children not vaccinated for religious, philosophical, or medical reasons was less than 1 percent. In Counties A and B, where 94 percent of the patients resided, similar rates of two-dose coverage were reported — 98 percent of kindergarteners (2100 of 2139) and nearly 100 percent of sixth graders (2299 of 2307).

Persons Declining Vaccination

On notification of the first recognized case of measles, personnel at the Indiana State Department of Health contacted church officials. The church had no position on immunization, and its officials actively cooperated with measures to contain the disease. The church reported its membership at approximately 500 persons, most of whom were characterized by church officials as white, middle class, and well educated. The church estimated that 35 of its members declined vaccination, primarily out of concern for adverse events. Of these, 31 (89 percent) became infected. According to representatives of six families who declined vaccination, issues considered important in their decision to refuse the vaccine were media reports of the dangers of the vaccine (e.g., the putative association between measles vaccination and autism, as well as the perceived effects of the vaccine preservative thimerosal) and a preference for naturally acquired immunity. The group that refused the vaccine was considered to be well integrated into the general community, creating the potential for multiple exposures and generalized transmission.

Containment Measures and Costs

Efforts were made to contact all families who had been present at the church gathering. Patients were advised to remain in isolation for 4 days after the onset of rash, and nonimmune family members were asked to be voluntarily quarantined for up to 18 days after exposure. Ten families in the church congregation who declined vaccination had at least one family member who was eligible for the measles vaccine before the outbreak. Although 9 of the 10 families still had members who were eligible for vaccination during efforts to control the outbreak, only 2 families agreed to vaccination. However, no legal actions were required to enforce other containment measures. Local health care facilities administered 148 doses of the measles, mumps, and rubella (MMR) vaccine to exposed, nonimmune persons. Hospital A, which employed the infected phlebotomist, had not previously required written documentation of the vaccination status of its employees. Therefore, daily screening of all staff for rash and fever was instituted at shift changes for one incubation period. Hospital A administered 317 doses of MMR vaccine and 210 doses of prophylactic immune globulin.

Table 2. Table 2. Estimated Direct Costs of Containing Measles during the Outbreak in Indiana.

In aggregate, containment activities involved approximately 3650 person-hours, 4800 telephone calls, 5500 miles driven, and 550 laboratory specimens tested (Table 2). Costs of containment were $167,685 ($4,932 per patient). The hospital employing the infected health care worker accrued 68 percent of the costs, creating a hospital-specific cost of more than $113,647.