Challenges to implementing second-dose varicella vaccination during an outbreak in the absence of a routine 2-dose vaccination requirement--Maine, 2006.

In June 2005, the Advisory Committee on Immunization Practices (ACIP) recommended administering a second dose of varicella vaccine during outbreaks, supplementing the routine 1-dose requirement. From October 2005 to January 2006, a varicella outbreak occurred in Maine in a highly vaccinated elementary school population. We investigated the outbreak, held a school-based vaccination clinic, and assessed costs in implementing ACIP's outbreak-response recommendation. Parents completed questionnaires and case investigation interviews. Personnel at the Maine Center for Disease Control and Prevention, the school in which the outbreak occurred ("school A"), and physician offices completed economic surveys. Forty-eight cases occurred, with no hospitalizations or deaths. Vaccine effectiveness was 86.6% (95% confidence interval, 82.0%-90.1%). Of 240 eligible students, 132 (55.0%) received second-dose vaccination. Implementing ACIP's outbreak-response recommendation was challenging and cost approximately $26,875. Additionally, the routine 1-dose varicella vaccination policy did not confer adequate population immunity to prevent this outbreak. These findings support ACIP's June 2007 recommendation for a routine 2-dose varicella vaccination program.

Recent resurgence of mumps in the United States.

BACKGROUND: The widespread use of a second dose of mumps vaccine among U.S. schoolchildren beginning in 1990 was followed by historically low reports of mumps cases. A 2010 elimination goal was established, but in 2006 the largest mumps outbreak in two decades occurred in the United States. METHODS: We examined national data on mumps cases reported during 2006, detailed case data from the most highly affected states, and vaccination-coverage data from three nationwide surveys. RESULTS: A total of 6584 cases of mumps were reported in 2006, with 76% occurring between March and May. There were 85 hospitalizations, but no deaths were reported; 85% of patients lived in eight contiguous midwestern states. The national incidence of mumps was 2.2 per 100,000, with the highest incidence among persons 18 to 24 years of age (an incidence 3.7 times that of all other age groups combined). In a subgroup analysis, 83% of these patients reported current college attendance. Among patients in eight highly affected states with known vaccination status, 63% overall and 84% between the ages of 18 and 24 years had received two doses of mumps vaccine. For the 12 years preceding the outbreak, national coverage of one-dose mumps vaccination among preschoolers was 89% or more nationwide and 86% or more in highly affected states. In 2006, the national two-dose coverage among adolescents was 87%, the highest in U.S. history. CONCLUSIONS: Despite a high coverage rate with two doses of mumps-containing vaccine, a large mumps outbreak occurred, characterized by two-dose vaccine failure, particularly among midwestern college-age adults who probably received the second dose as schoolchildren. A more effective mumps vaccine or changes in vaccine policy may be needed to avert future outbreaks and achieve the elimination of mumps.

Implications of a 2005 measles outbreak in Indiana for sustained elimination of measles in the United States.

BACKGROUND: Measles was declared eliminated from the United States in 2000 but remains endemic worldwide. In 2005, a 17-year-old unvaccinated girl who was incubating measles returned from Romania, creating the largest documented outbreak of measles in the United States since 1996. METHODS: We conducted a case-series investigation, molecular typing of viral isolates, surveys of rates of vaccination coverage, interviews regarding attitudes toward vaccination, and cost surveys. RESULTS: Approximately 500 persons attended a gathering with the index patient one day after her return home. Approximately 50 lacked evidence of measles immunity, of whom 16 (32 percent) acquired measles at the gathering. During the six weeks after the gathering, a total of 34 cases of measles were confirmed. Of the patients with confirmed measles, 94 percent were unvaccinated, 88 percent were less than 20 years of age, and 9 percent were hospitalized. Of the 28 patients who were 5 to 19 years of age, 71 percent were home-schooled. Vaccine failure occurred in two persons. The virus strain was genotype D4, which is endemic in Romania. Although containment measures began after 20 persons were already infectious, measles remained confined mostly to children whose parents had refused to have them vaccinated, primarily out of concern for adverse events from the vaccine. Seventy-one percent of patients were from four households. Levels of measles-vaccination coverage in Indiana were 92 percent for preschoolers and 98 percent for sixth graders. Estimated costs of containing the disease were at least 167,685 dollars, including 113,647 dollars at a hospital with an infected employee. CONCLUSIONS: This outbreak was caused by the importation of measles into a population of children whose parents had refused to have them vaccinated because of safety concerns about the vaccine. High vaccination levels in the surrounding community and low rates of vaccine failure averted an epidemic. Maintenance of high rates of vaccination coverage, including improved strategies of communication with persons who refuse vaccination, is necessary to prevent future outbreaks and sustain the elimination of measles in the United States.