Measles elimination in the Americas. Evolving strategies.

The strategy currently used to control measles in most countries has been to immunize each successive birth cohort through the routine health services delivery system. While measles vaccine coverage has increased markedly, significant measles outbreaks have continued to recur. During the past 5 years, experience in the Americas suggests that measles transmission has been interrupted in a number of countries (Cuba, Chile, and countries in the English-speaking Caribbean and successfully controlled in all remaining countries. Since 1991 these countries have implemented one-time "catch-up" vaccination campaigns (conducted during a short period, usually 1 week to 1 month, and targeting all children 9 months through 14 years of age, regardless of previous vaccination status or measles disease history). These campaigns have been followed by improvements in routine vaccination services and in surveillance systems, so that the progress of the measles elimination efforts can be sustained and monitored. Follow-up mass vaccination campaigns for children younger than 5 years are planned to take place every 3 to 5 years.

Improving disease reporting in Los Angeles County: trial and results.

A telephone survey of physicians in Los Angeles County revealed that 50 percent of 405 contacted were unaware of the legal mechanism for reporting communicable diseases--the Confidential Morbidity Report (CMR) card. After that survey, three measures were taken in an effort to improve reporting and surveillance: (a) use of a stamped self-addressed CMR postcard, (b) publication of the monthly newsletter "Public Health Letter," which was distributed to 23,000 health professionals in Los Angeles County free of charge, and (c) initiation of an active disease surveillance system that included 171 reporting sites contacted weekly (76 physicians, 36 schools, 33 preschools, 22 hospitals, and 4 university student health centers). No increase in the levels of disease reporting was observed, based on 4 years' experience with the revised CMR card and the Public Health Letter. The active disease surveillance system, however, has provided anecdotal reports of disease occurrence and notification of outbreaks of both reportable and nonreportable diseases. Moreover, the authors believe it has improved rapport between the county health department and the medical community.

Amebic infections in asymptomatic homosexual men, lack of evidence of invasive disease.

A survey for enteric infections in 140 asymptomatic homosexual men who attended a community clinic revealed a high prevalence of infection with Entamoeba histolytica (27.1 per cent) and Giardia lamblia (15.7 per cent). In contrast, the prevalence of elevated indirect hemagglutination (IHA) titers (greater than or equal to 1:128), which indicate invasive amebiasis, was low (5.7 per cent). Our findings suggest that only a limited amount of invasive amebic disease is occurring in this group of homosexual men.

Influenza in the elderly: report of an outbreak and a review of vaccine effectiveness reports.

An outbreak of influenza A in nursing home residents is reported and other studies of influenza vaccine effectiveness in elderly populations are reviewed. The outbreak occurred in a Los Angeles nursing home between February and March 1983. Of the 87 residents, 46 (53%) were affected with influenza-like illness. Attack rates were similar between immunized and unimmunized residents (52% versus 58%), and yielded a vaccine effectiveness estimate of 10%. No additional protection could be demonstrated in residents who received vaccine for two consecutive years. Seven persons died (mortality rate of 8.1%); the mortality rate was greater in the unimmunized (15.8%) than in the immunized (6.2%). Because this study and other field studies of influenza vaccine are limited in precision and power, a statistical summary of the various studies was constructed. Summarizing the studies of institutionalized elderly (in hospitals and nursing and retirement homes) yielded an estimate of 74% for the average vaccine effectiveness in mortality reduction, and an estimate of 33% for the average effectiveness in preventing clinical illness. For the non-institutionalized elderly, the corresponding estimates were 47% for mortality, and 5% for clinical illness. Despite the obvious limitations of such summaries, it seems reasonable to conclude that influenza vaccines have on the average been of clear benefit in the institutionalized elderly, while the benefits in the non-institutionalized elderly have been less dramatic and may warrant further investigation.

Clinical effectiveness of rubella vaccine in a college population.

An outbreak of rash-like illness compatible with rubella occurred among the student population of a large university in Los Angeles between November 1, 1981 and January 31, 1982. A case-control study was conducted in order to estimate the effectiveness of rubella vaccine in preventing clinical rubella in this university population. Immunization and disease histories were obtained from parents and physicians for 39 cases and 86 controls. For those students with a clear documentation of immunization history, only one of 16 cases (6%) had evidence of prior rubella immunization, compared with 40 of 56 controls (71%). This yielded an estimated vaccine effectiveness of 97% (95% confidence limits of 82% to 100%). The level of protection observed for students immunized with rubella vaccine in our study population was high and comparable to that reported in other recent studies. This supports the notion that the current large reservoir of young adult susceptibles is primarily attributable to past failures to vaccinate school-age children, rather than vaccine failures.

An outbreak of respiratory syncytial virus pneumonia in a nursing home for the elderly.

An outbreak of pneumonia and febrile respiratory illness took place in a Los Angeles County nursing home for the elderly in February and March of 1979. Forty of 101 (40%) residents were affected. Twenty-two (55%) had pneumonia and eight (20%) died. The outbreak extended over a period of 6 weeks. Serological evidence implicated respiratory syncytial virus (RSV) as the causative agent. Three patients had fourfold or greater rises in the titre of antibody to RSV, one had high titres in paired samples of serum, while nine had a titre of greater than or equal to 64 in a single convalescent sample. RSV may be a more important cause of lower respiratory illness among the elderly in residential institutions than previously recognised.

Rubella in hospital employees.

In early 1982, 15 hospitals in Los Angeles County reported one or more serologically confirmed rubella cases among their employees. Secondary cases occurred at eight hospitals; overall, 56 cases were identified among employees, of which 28 were serologically confirmed. Testing of 2,061 employees revealed 1,770 (86%) with detectable antibody. A survey of 83 hospitals offering obstetrical services indicated only 42% (33 of 78) had an established rubella screening policy. Based on the results of this survey, the Los Angeles County Department of Health Services published recommendations for hospital rubella screening and immunization policies.

A population-based case-control study of anencephalus and spina bifida in a low-risk area.

For the period 1973 to 1977, a total of 536 cases of anencephalus and spina bifida were ascertained in Los Angeles County, California, a low-risk area, and compared with a 2 per cent random sample of all live births in the county. Women with Spanish surnames had an elevated risk for anencephalus and to a lesser extent for spina bifida; Blacks were at lowest risk, especially for spina bifida. The occurrence of a previous fetal death was a strong risk factor for anencephalus but there was no association between socio-economic status and either of the defects. Advanced maternal age was a stronger risk factor for spina bifida than for anencephalus but, as in other studies in low-risk areas, no increased risk was observed among teenage mothers. Paternal age did not show any independent association after controlling for mother's age. Finally, the association of high birth-order with the birth defects was weakened greatly after simultaneous adjustment for age and ethnicity.

Tetanus and diphtheria immunity in an elderly population in Los Angeles County.

Fifty-four per cent of 246 subjects attending senior citizen centers (mean age 69), and 29 per cent of 111 convalescent hospital subjects (mean age 82) had protective levels of tetanus antitoxin (greater than or equal to 0.01 units/ml). Age-specific immunity levels were lower for females than males, and generally decreased with age. Forty-eight and one-half per cent of the senior citizen center subjects and 55.9 per cent of the convalescent hospital subjects had protective levels of diphtheria antitoxin (greater than or equal to 0.01 units/ml).

Serological survey: immunity to vaccine preventable diseases among detainees at a Juvenile Hall facility.

Sera from 378 juveniles interned in a juvenile hall facility between February and March, 1978, were tested for antibody to polio viruses types 1, 2, and 3; diphtheria; tetanus; measles; and rubella. Only 57% of juveniles ages 11-18 years had neutralizing antibody greater than or equal to 1:8 to all three types of polio viruses. Juveniles most often lacked antibody to polio type 3. Over 92% of juveniles tested had a protective level of antitoxin (greater than or equal to .01 U/ml) to diphtheria and tetanus. Hemagglutination inhibition (HAI) antibody tests performed for measles and rubella revealed 87.5% and 81% with titers greater than or equal to 1:8 respectively. No major differences in immune status were found between those with a previously documented vaccination history and those without. Based on these data a uniform immunization policy was adopted for Los Angeles County's Juvenile Hall facilities.

The global eradication of smallpox.

On May 8, 1980, the 33rd World Health Assembly declared the world free of smallpox. This followed approximately 2 1/2 years after the last documented naturally occurring case of smallpox was diagnosed in a hospital worker in Merca, Somalia. A major breakthrough for the eventual control of this disease was the discovery of an effective vaccine by Edward Jenner in 1796. In 1966 the World Health Assembly voted a special budget to eliminate smallpox from the world. At that time, smallpox was endemic in more than 30 countries. Mass vaccination programs were successful in many Western countries; however, a different approach was taken in developing countries. This approach was known as surveillance and containment. Surveillance was aided by extensive house-to-house searches and rewards offered for persons reporting smallpox cases. Containment measures included ring vaccination and isolation of cases and contacts. Hospitals played a major role in transmission in a number of smallpox outbreaks. The World Health Organization is currently supporting several control programs and has not singled out another disease for eradication. The lessons learned from the smallpox campaign can be readily applied to other public health programs.

Animal bites: patterns of treatment.

Between 1972 and 1979, more than 350,000 animal bite incidents were reported to the Los Angeles County Department of Health Services. Each incident was investigated by county health authorities. To determine the type of treatment given to animal bite victims, a mailed questionnaire was sent to 1,201 persons selected from the 1972 report files. Eighty-nine percent of respondents received treatment for animal bite. The most frequent treatment (64.5%) was tetanus immunization alone or with cleaning and bandaging of the wound. Three of the 710 respondents (0.4%) received post-exposure antirabies treatment. The authors discuss recommendations for treatment of animal bites.

Rubella outbreak among hospital employees.

A rubella outbreak among medical staff on the obstetric service of a large Los Angeles hospital was studied. Fifteen cases of suspected rubella were reported among hospital personnel during a 2-month period in 1978. Of these, 4 were confirmed, 2 by viral isolation and serology and 2 by serologic study alone. A fifth case, the index, had a convalescent-phase serum with an elevated rubella hemagglutination inhibition (HAI) antibody titer. A list of 231 pregnant women who may have been exposed to any of the 15 suspect cases was assembled. The authors succeeded in contacting and obtaining postexposure sera for only 140 (61%) of the exposed women. Thirty-five (25%) of these women were without detectable rubella HAI antibody. A second serum sample was obtained from 93 women 2 to 3 weeks after the first, and no fourfold rises in titer were observed. To evaluate those with suspicious high stationary titers, 60 specimens were selected for immunoglobulin M (IgM) testing. Only 1 was positive for IgM antibody. A postexposure illness survey revealed that 20 (15%) of 130 women reported various rash-like illnesses after their visit to the hospital. There were no reports of affected offspring in any of the exposed women. Four hundred ten staff members submitted sera for antibody testing; 76 (19.2%) were without detectable rubella HAI antibody. This outbreak is discussed in light of recent changes in rubella epidemiology, and several recommendations for hospital policy are proposed.

Vaccine failures in the epidemiology and control of measles.

Data were employed from confirmed measles case reports and an immunization survey to estimate the apparent effectiveness of measles vaccine in Los Angeles County in 1976. We evaluated the age-specific proportions of our case load arising from persons erroneously thought to possess immunity. Thirty five per cent of our cases claimed to have had prior measles vaccination, and over 60 per cent of these reported having written records. Since community measles control programs rely on immunization records as the principal screening tool, the shortcomings observed need to be recognized.