Mass vaccination campaign following community outbreak of meningococcal disease - Research

Emerging Infectious Diseases, Dec, 2002 by Gerard Krause, Carina Blackmore, Steven Wiersma, Cheryll Lesneski, Laurey Gauch, Richard S. Hopkins

During December 12-29, 1998, seven patients ages 2-18 years were diagnosed with serogroup C meningococcal disease in two neighboring Florida towns with 33,000 residents. We evaluated a mass vaccination campaign implemented to control the outbreak. We maintained vaccination logs and recorded the resources used in the campaign that targeted 2- to 22-year-old residents of the two towns. A total of 13,148 persons received the vaccinations in 3 days. Vaccination coverage in the target population was estimated to be 86% to 99%. Five additional cases of serogroup C meningococcal disease occurred in the community during the year after the campaign began, four in patients who had not received the vaccine. The cost of control efforts was approximately $370,000. Although cases continued to occur, the vaccination campaign appeared to control the outbreak. Rapid implementation, a targeted approach, and high coverage were important to the campaign's success.

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Neisseria meningitidis is a leading cause of bacterial meningitis and sepsis in children and young adults in the United States (1,2). An estimated 2,600 cases occur each year, most of them sporadic (2). Between 10 and 15 outbreaks of meningococcal disease are reported in the country annually (1,3). Outbreaks can occur in institutions as well as in communities. Communitywide outbreaks can persist for several months, and controlling them remains a major challenge in public health (4--6).

The primary method for preventing sporadic meningococcal disease is chemoprophylaxis of close contacts after a case is identified (1,7,8). However, the protective effect of chemoprophylaxis is of limited duration (6,9,10).

A quadrivalent polysaccharide meningococcal vaccine effective against N. meningitidis serogroup A, C, W135, and Y is available in the United States (7,11). Serogroup C N. meningitidis accounts for most U.S. outbreaks (3). The Advisory Committee on Immunization Practices (ACIP) has released recommendations for the use of meningococcal vaccine to control outbreaks of serogroup C meningococcal disease (11).

Identifying the need for a vaccination campaign, defining the target population, implementing the campaign rapidly, and achieving high vaccination coverage are difficult (5). Mass vaccination campaigns require major logistic efforts and often take place in an atmosphere of public anxiety (5,6,12,13). Few local and state health departments have much experience in responding to such outbreaks. Mass vaccination campaigns in response to meningococcal disease outbreaks have been reported before, but only limited information is available on the operational aspects of such efforts (4,5,9,14).

In December 1998, two neighboring towns with a combined population of 33,000 persons in Putnam County, Florida, had a community outbreak of meningococcal disease (1,3). The health department administered chemoprophylaxis to close contacts of the case-patients and investigated links between patients. Detailed results of the investigation have been described elsewhere (15). On December 29, 1998, the decision was made to implement a mass vaccination campaign to control the outbreak in the community, based on ACIP recommendations (7). We describe the epidemiology of the outbreak and the methods used for providing chemoprophylaxis and implementing the vaccination campaign. We also evaluate the results and the cost of the control efforts.

Materials and Methods

Case Definition

A case-patient was defined as a person in Putnam County with onset of clinically compatible illness after November 1998 and isolation of serogroup C N. meningitidis obtained from a normally sterile site or detection of serogroup C meningococcal polysaccharide antigen in the cerebrospinal fluid or serum (7). Pulsed-field gel electrophoresis (PFGE) was performed on culture-confirmed isolates in the state health department laboratory by using previously described methods (16,17).

Chemoprophylaxis

Chemoprophylaxis--rifampin, ciprofloxacin, or ceftriaxone, as recommended by ACIP (7)--was given to close contacts. A close contact was defined as a household member, day-care center contact, or anyone directly exposed to the patient's oral secretion (7,18). We documented all chemoprophylaxis provided by the health department for the first nine patients and retrospectively verified whether the persons who had received prophylaxis met the definition of a close contact.

Vaccination Campaign

The decision to implement the vaccination campaign was based on ACIP guidelines for community-based outbreaks (7). We defined the population at risk as the population of the two neighboring towns since this area represented the smallest geographically contiguous population that included all case-patients. The target population for the vaccination campaign was defined as all residents ages 2-22 years.

The vaccination campaign took place December 30-31, 1998, and January 2, 1999. Additional vaccinations were offered at the health department by appointment until January 20, 1999, for those who belonged to the target group but did not receive the vaccine during the 3-day campaign.