Mild measles and secondary vaccine failure during a sustained outbreak in a highly vaccinated population

Article Abstract:

From an all time low of 1,497 cases in 1983, the incidence of measles has steadily risen in the US, and in 1989, 14,000 cases were reported. Forty percent of all new measles cases occurred in children who were previously vaccinated. Primary vaccine failure, or failure to develop immunity as a result of vaccination, is considered the cause of most new cases of measles in this country. Sometimes a mild case of measles develops in a previously vaccinated individual; this is referred to as secondary vaccine failure. This phenomenon was examined during an outbreak of measles which occurred between January and September of 1986 in a school district in Wisconsin. Diagnoses, using the Centers for Disease Control criteria, were confirmed clinically or by seroconversion (blood serum tests). A total of 235 cases of measles-like symptoms were reported; 218 were diagnosed as measles. Thirty-six of these cases were in unvaccinated individuals; 182 occurred in previously vaccinated subjects. Of the unvaccinated group, 22 cases were clinically confirmed, and 14 cases of measles were confirmed serologically. In the vaccinated group, a smaller proportion (74 of 182 cases) were clinically confirmed than were serologically confirmed (108 cases). The majority of mild cases of measles were found in vaccinated subjects, and were considered to be a result of secondary vaccine failure. Although still considered mild, these cases, for the most part, were not clinically distinguishable from classic measles illness in unvaccinated individuals. Of the 108 previously vaccinated subjects with serologically confirmed measles,, 10 individuals showed no measles-specific IgM (an immunoglobulin) response and had a milder illness than any of the other subgroups. It was concluded that, although the phenomenon of secondary measles vaccine failure may cause an underreporting of cases and overestimation of vaccine efficacy, this vaccine-modified type of measles is not a primary problem in measles control. (Consumer Summary produced by Reliance Medical Information, Inc.)

Case studies, Measles vaccine, Measles vaccines

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Risk factors for measles in a previously vaccinated population and cost-effectiveness of revaccination strategies

Article Abstract:

Although vaccination against measles is highly effective, outbreaks of the disease among children who have been vaccinated continue to occur. The type of revaccination program to be implemented to protect children after an outbreak, however, should be selected at least partly on the basis of its cost-effectiveness. To learn more about the effectiveness of revaccination in such cases, a measles outbreak in Wisconsin in 1986 among highly vaccinated schoolchildren was studied. Two hundred nineteen cases of measles were recorded; the initial case had undergone vaccination twice, at the ages of 12 months and 8 years. The measures to control the outbreak consisted of vaccinating students who had not been vaccinated and those whose first vaccination had taken place at an age earlier than 12 months. One hundred seventy cases had undergone measles vaccination before the outbreak; 144 control subjects (also previously vaccinated) were members of the same households as cases, but did not develop measles. Cases and controls were compared to better understand why vaccination had failed for the former group. The costs of four hypothetical revaccination programs were calculated. Results showed that the risk of contracting measles was higher for those vaccinated before the age of 15 months than for those vaccinated after this age. Children vaccinated before a stabilizer was added to the measles vaccine in 1979 were also at higher risk than those vaccinated after the stabilizer. Vaccinated siblings of cases had a lower rate of contracting the disease than unvaccinated siblings (5 and 67 percent, respectively). Revaccination of the two groups at highest risk, or of all students, might have prevented many cases. The costs of such programs are estimated. Since identification of the schoolchildren most likely to be at risk is difficult in specific cases, revaccination of all students at risk is the strategy most likely to be employed. (Consumer Summary produced by Reliance Medical Information, Inc.)

Economic aspects, Prevention, Risk factors, Children, Vaccination of children, Vaccination, Preventive medicine, Preventive health services for children

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A pertussis outbreak in a Wisconsin nursing home

Article Abstract:

Bordetella pertussis is a gram-negative bacteria that causes lung infections and whooping cough in children and adults. It can produce symptoms of varying severity ranging from a mild lung infection to a prolonged cough with shortness of breath and vomiting. During the summer and fall of 1985, a large outbreak of pertussis occurred in two rural communities in central Wisconsin. The outbreak spread to a local nursing home, which had 107 residents and 116 employees. Blood samples from 105 of the residents and 104 of the employees were tested for antibodies to pertussis. Thirty-eight of the residents and eight of the employees tested positive for pertussis. In addition, four of the residents had positive bacterial cultures for pertussis. These four residents had persistent coughing that lasted from 43 to 54 days. The nursing home residents between the ages of 70 and 79 appeared to have the greatest risk for illness. None of the affected residents had shortness of breath or vomiting and all recovered without complications. Following testing, residents and employees received prophylactic (preventive) treated with erythromycin for 7 to 14 days. At the present time it is not known how pertussis was introduced into the nursing home. The authors advise that people who suffer from prolonged coughing, particularly those living in a community were pertussis is known to be present, may have a pertussis infection. Early diagnosis is important because oral erythromycin can reduce the severity of the illness and can prevent infection in people who come in contact with the bacteria. (Consumer Summary produced by Reliance Medical Information, Inc.)

Diseases, Nursing homes, Nursing home patients, Wisconsin, Bordetella pertussis, Whooping-cough, Whooping cough

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