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Mortality data in this table are voluntarily reported from 121 cities in the United States, most of which have populations of 100,000 or more A death is reported by the place of its occurrence and by the week that the death certificate was filed Fetal deaths are not included.

** Pneumonia and influenza

↑ Because of changes in reporting methods in these 4 Pennsylvania cities, these numbers are partial counts for the current week Complete counts will be available in 4 to 6 weeks

+ Total includes unknown ages

Mumps - Continued

nearly seven times more likely to be susceptible to mumps than students in other grades (p < 0.001) (Table 2).

Since initial reports suggested that many mumps cases occurred in children known to have been vaccinated, a vaccine efficacy study was done. The sixth grade was used to estimate vaccine efficacy, because it represented 52% of the school's cases and had enough unvaccinated and vaccinated students to make calculation of attack rates in these two groups meaningful. Vaccination status was verified for both vaccinated and unvaccinated students using a dated parental record. If unavailable, a physician record was then obtained. Studies

*Vaccine efficacy was estimated by the standard method:

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where VE is the vaccine efficacy in percent; ARU is the attack rate in the unvaccinated; and ARV is the attack rate in the vaccinated.

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NOVEMBER

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OCTOBER
DECEMBER

ONSET (2-DAY PERIODS)

TABLE 1. Enrollment, case count, and attack rate of mumps, by grade*
School A, Atlantic County, New Jersey, October-December 1983

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"Grades 1 and 2 are located in a separate school.

*Between sixth grade and K-5; 95% confidence interval = 3.0-8.5; p < 0.001.

Mumps - Continued

relying solely on school records for determination of immunization status and casefinding may provide misleadingly low estimates of vaccine efficacy (2). Vaccine efficacy was estimated to be 91% for sixth graders, with a 95% confidence interval of 77%-93% (Table 3). The attack rate in the vaccinated children in the sixth grade was 4% and fell within the 5%-10% primary vaccine failure rate observed in clinical trials (3).

Outbreak control began with a review of all student immunization records in the school district to identify students lacking mumps vaccination. Students deficient in measles, rubella, diphtheria, and tetanus vaccinations were also identified. Vaccines were offered free to all susceptible schoolchildren in three state-run vaccination clinics held for 2 days in early December. Of 4,188 students in the district, 945 (23%) were identified as lacking mumps immunity, based on criteria of the Immunization Practices Advisory Committee (ACIP) (1). Of the 945 susceptible students, approximately 75% received vaccines containing mumps antigen at the state-run clinics. An unknown number of students was vaccinated by private physicians.

Telephone questionnaires administered to the parents of ill students were used to collect information on the economic impact of the outbreak. The 63 cases of mumps occurred in children from 46 different households. The total cost to households was $4,687 for an average cost of $102 per household. The average number of school days missed by each child was 5.7. Of the 46 households, 16 (35%) had at least one parent miss 1 day of work to take care of a child, with a mean of 3 days of work missed. Day-care services were used by six (13%) households. Medical services were utilized by 33 (72%) households. All these households consulted with their physicians by telephone, and three (7%) households took a child to a hospital emergency room. No persons were hospitalized.

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*These data are based on school records only.

*Between sixth grade and K-5; 95% confidence interval = 4.5-9.9; p < 0.001.

TABLE 3. Mumps vaccine efficacy for the sixth grade, based on school, parental, and physician records Elementary School A, Atlantic County, New Jersey

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*Vaccine efficacy = 91%; 95% confidence interval = 77%-93%.

*Excludes one student whose illness could not be distinguished from a vaccine failure or incubation of

se at the time of vaccination.

Mumps - Continued

The cost associated with the emergency vaccination clinics was $6,250, which included costs for clinic supplies, personnel, transportation, and vaccine. The cost of vaccine alone was $3,100, or 50% of the total clinic cost. The total direct cost of the outbreak was $10,937 (this includes clinic costs plus the total costs to households). Even though 362 pupil school days were lost because of illness associated with this outbreak, there was no loss of state school reimbursement aid, since New Jersey does not consider absenteeism when providing aid to local school districts.

Reported by J Aiello, Atlantic County Health Dept, R Altman, L Dimasi, C Kauffman, TKsell, R McCready, S Sloane, WE Parkin, DVM, State Epidemiologist, New Jersey State Dept of Health; Div of Field Svcs, Epidemiology Program Office, Div of Immunization, Center for Prevention Svcs, CDC.

Editorial Note: Although mumps has never attained the same notoriety as measles or rubella in the public or medical community, mumps virus was the leading cause of viral encephalitis of known etiology in this country until 1975 (4). The routine use of combined measlesmumps-rubella (MMR) vaccine in recent efforts to increase protection rates for measles and rubella has had a beneficial effect on the reported mumps incidence. A provisional total of 3,285 mumps cases were reported nationally in 1983-the lowest reported incidence since mumps became a nationally notifiable disease in 1968. Peak mumps reporting occurred in 1967, the year of vaccine licensure, with 185,691 cases. Cases in 1983 decreased by 38% from 1982 (5,310 cases) and by 98% from 1967.

Age-specific data are not yet available for 1983. Data for 1982 indicate the risk of infection has declined by more than 90% for all age groups. However, the reported incidence rate for 10- to 14-year-olds in 1982 was higher than that for any other age group (5). In the years immediately following vaccine licensure, the highest incidence rates occurred in 5- to 9year-olds, followed by children under 5 years of age. The age-specific changes in mumps infection rates are similar to those noted for measles and rubella and would be expected with any vaccination policy oriented towards schoolchildren (1). Thus, based on mumps epidemiology alone, the outbreak in New Jersey involving largely sixth grade and older children was not unexpected.

Mumps immunity was not required for school entry in New Jersey until 1978. Vaccination of this group with the highest susceptibility rates (5) allowed the most efficient allocation of limited resources. In New Jersey, immunity could be proven by evidence of appropriately administered mumps vaccine, parental, or medical provider history of mumps or positive mumps serology. In this outbreak, the immunization law established two cohorts of students varying in their degrees of mumps immunity divided at the fifth- and sixth-grade levels-thus affecting the pattern of this outbreak.

Since the attack rate for each grade was directly proportional to the percentage of unvaccinated students, the higher attack rate for sixth graders most likely reflected the fact that sixth graders were not covered by the law. Compliance with the law, as reflected in vaccine coverage rates, was greater than 95%. Thus, poor compliance with the school vaccination law did not lead to this outbreak. Rather, it was those grades not covered by the school law that provided the susceptibles that allowed the disease to spread. A more comprehensive immunization law might have further limited both the size and scope of the outbreak.

Twenty states currently do not require proof of mumps immunity for school entry. Of the 30 states that do require mumps immunization, 15 have laws that affect only first entry to school, and 15 have laws that affect children in kindergarten or higher grade levels. Thirteen states require proof of mumps immunity for grades K-12.

Vaccine efficacy for the sixth grade was 91%. The estimate of vaccine efficacy in this study is consistent with earlier clinical evaluations that have noted vaccine efficacy ranging between 75% and 90% (2,3). Since more than 90% of cases in the fifth grade were in vac*Not acceptable according to ACIP recommendations.

Mumps - Continued

cinated individuals, ineffectiveness of vaccine was considered a possible cause of illness. However, the overall vaccination level was in excess of 95%, and this distribution of cases is to be expected.

The economic impact was substantial to households and to the government agencies involved in providing emergency immunization clinics. The cost estimate did not include loss of reimbursement funds due to school absenteeism. However, in states with such reimbursement, the cost may be quite significant. For example, in neighboring New York, where absenteeism does affect reimbursement aid, a loss of 362 pupil days would result in a loss of $2,349 to a local school district. This is based on a New York mean reimbursement amount of $6.49 per student per day.

A recent study has shown the positive benefit-cost ratio of mumps vaccine in susceptible populations (6). When administered as MMR vaccine, mumps vaccine has a benefit-to-cost ratio of 7:1 using reported cases and 39:1 using estimates of actual disease incidence. References

1. Immunization Practices Advisory Committee. Mumps vaccine. MMWR 1982;31:617-20, 625.

2. CDC. Efficacy of mumps vaccine-Ohio. MMWR 1983;32 391-2,397-8.

3. Hilleman MR, Buynak EB, Weibel RE, Stokes J Jr. Live, attenuated mumps-virus vaccine. N Engl J Med 1968;278:227-32.

4. CDC. Mumps surveillance, July 1974-December 1976, Issued July 1978.

5. CDC. Mumps-United States, 1980-1983. MMWR 1983;32:545-7.

6. Koplan JP, Preblud SR. A benefit-cost analysis of mumps vaccine. Am J Dis Child 1982;136:362-4.

Heat-Associated Mortality - New York City

The estimated annual death rate in New York City based on data collected during the week ending Friday, June 15, 1984, was 1,343 per 100,000 population, a 35% increase over the average rate for the preceding 4 weeks (Figure 7). This was the highest mortality rate recorded in New York City since January 1981 and was associated with a sudden and severe heat wave-mean daily temperatures rose from 21.1 C (70 F) in the preceding week to 28.9 C (84 F). The greatest increase was for persons aged 75 years and over, among whom the death rate increased 47%. The death rate for elderly women increased more than for elderly men (Figure 8). Among those aged 75-84 years, death rates rose 39% for men, compared with 66% for women; among those over 85 years old, increases were 13% for men and 55% for women.

The increased number of deaths was almost exclusively among nonhospitalized persons living at home (Table 4). Among persons 65 years or older, there was a 150% increase in the number of deaths occurring at home. There were only small changes in the number of deaths occurring in hospitals or nursing homes.

These data suggest that the noninstitutionalized elderly, particularly women, are at highest risk of heat-associated death. Programs are needed to protect this relatively small but sensitive group during prolonged or severe heat.

Reported by AR Kristal, DrPH, S Schultz, MD, DJ Sencer, MD, New York City Dept of Health; Special Studies Br, Chronic Diseases Div, Center for Environmental Health, CDC.

Editorial Note: This report is consistent with previous descriptions of the dramatic increases in total mortality that may accompany severe heat. Health effects of heat are particularly prominent in urban areas (1-6).

In previous episodes of this sort, physicians have attributed only 10%-60% of the excess deaths directly to the heat, e.g., by a diagnosis of heat stroke. Increases in deaths attributed to cerebrovascular disease and ischemic heart disease have accounted for a large part of the remainder of the excess (1,4-6). Although heat stress may aggravate underlying vascular dis*The arithmetic mean of the highest and lowest recorded temperatures.

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