Prevalence of rubella antibodies in Massachusetts schoolchildren.

In 1982, 1,871 (79%) of 2,368 eligible 6th, 10th and 12th grade students in Massachusetts participated in a statewide serosurvey for rubella antibodies. Sera were screened at the Centers for Disease Control (CDC) by a reference hemagglutination inhibition assay at 1:8, equivalent to approximately 15 International Units (IU)/ml. Sera negative by the CDC hemagglutination inhibition assay were retested using an enzyme immunoassay, a passive hemagglutination assay, and a commercial hemagglutination inhibition test. The approximate screening levels were 10 IU/ml, 7.5 IU/ml, and 5 IU/ml, respectively. Overall seroprevalence levels varied from 76.4% screening at 15 IU to 93.1% including seropositives from any of the tests. Persons with a school record of vaccination had significantly higher seroprevalence levels than persons without records. However, only 78.3% of persons with a record had antibody greater than or equal to 15 IU compared with 60.0% without records; considering any detectable antibody, the comparison is 95.6% versus 71.4%. The low titers in vaccinees appeared to be due to a falloff of antibody with time since vaccination. Of students with a single vaccination noted in the record with exact dates, 92.3% who were vaccinated 0-4 years prior to the study had antibody at 15 IU compared with less than 78% of students with antibody who were vaccinated five or more years prior to the study. In contrast, using more sensitive assays, there was no significant decline in seroprevalence with time since vaccination. Revaccination studies and epidemiologic data suggest that almost all persons with detectable antibody whether above or below 15 IU/ml are immune to rubella. Thus, immunity levels in Massachusetts schoolchildren in the 6th, 10th, and 12th grades are probably in excess of 90%.

Control of paralytic poliomyelitis in the United States.

The changing annual vaccination status of the population and the greater than 1,000-fold drop in reported annual incidence of paralytic poliomyelitis between the early 1950s and early 1970s indicate that the control of poliomyelitis in the United States must be attributed to the use of both the inactivated poliovirus vaccine and oral poliovirus vaccine. The containment, in 1972 and 1979, of rare epidemics in poorly vaccinated subpopulations and the existence of only three reported cases of paralytic poliomyelitis clearly attributable to wild poliovirus in the last three years document a major triumph for public health. The continuing occurrence of vaccine-associated paralysis (six or seven reported cases per year, 1980-1982) indicates the necessity, despite the accomplishments, for continued review of the current vaccination strategy.

Impact of measles in the United States.

Measles has had a severe impact on children in the United States since colonial times. In the early decades of the 20th century, thousands of fatal measles infections were reported each year. During the 1950s an annual average of greater than 500,000 cases of measles and nearly 500 deaths due to measles were reported in the United States. Surveys indicated that 95% of the population had been infected with measles by the age of 15 years. The introduction of measles vaccine and its widespread use, which began in 1963, has had a major impact on the occurrence of measles in the United States. Reported numbers of cases, deaths due to measles, and complications of measles (e.g., encephalitis) have declined dramatically. Accompanying the decline in reported incidence of measles and following it by approximately seven years, has been a decline in the reported incidence of subacute sclerosing panencephalitis (SSPE). In recent years, the incidence of measles has dropped to levels that are less than 1% of those seen in the prevaccine era. In 1981, provisional figures indicated that only 10% of counties in the United States reported any cases of measles. The reported incidence in 1981 was 1.3 cases per 100,000 population, compared with an average incidence of 336.3 cases per 100,000 population in the decade 1950-1959. Thus, the impact of measles in the United States has been markedly reduced, and it is anticipated that indigenous transmission will be eliminated entirely from the country within the year.

Elimination of indigenous measles from the United States.

In October 1978, a nationwide initiative to eliminate indigenous measles from the United States by October 1, 1982, was announced. The measles elimination program has three major elements: attaining and maintaining high immunization levels, aggressive and effective surveillance, and vigorous response to cases. In 1980, immunization levels in children entering school for the first time were 96%, indicating that the necessary levels have been attained in the age group. Mechanisms are in place to assure maintenance of these levels; these rely heavily on the use of immunization requirements for school attendance in each state. Aggressive surveillance systems have been developed for each state to detect suspected measles cases as soon as possible after they occur and to investigate them within 24 hr of notification. The clinical definition of measles used is fever of greater than or equal to 101 F (38.3 C); rash of three or more days duration; and cough, coryza, or conjunctivitis. The response to outbreaks involves identifying persons in the area who are at risk of contracting measles, determining those who are possibly susceptible, and ensuring that these persons are vaccinated. In school outbreaks, susceptible students are vaccinated or excluded from school until the outbreak is over. During 1981, measles morbidity reached a record low level of only 3,032 reported cases (provisional total). Epidemic measles occurred in only a few outbreaks of limited size and duration, and endemic cases were restricted to a small number. Imported cases averaged slightly more than two per week, occasionally producing limited outbreaks, but more often resulting in no secondary spread. Transmission of measles has been interrupted in most of the United States. With continued vigorous implementation of the current strategy and with additional measures to lessen the risk of importations, it appears likely that the goal to eliminate indigenous measles transmission will be attained by October 1982.

Measles mortality in the United States 1971-1975.

During 1971-75, an average of 35.4 measles-related deaths were recorded each year; one death for every 1,000 measles cases reported. Measles mortality rate was highest in children under 1 year of age, as was the death-to-case ratio. Mortality rates were higher in non-metropolitan than in metropolitan counties. Measles mortality rates were inversely related to median family income.

Risk factors in subacute sclerosing panencephalitis: a case-control study.

Fifty-two persons with subacute sclerosing panencephalitis (SSPE) were compared with playmate and hospital controls matched for age, sex, and race. Persons with SSPE were more likely to have had measles than their age-matched controls. The age at measles infection for children with SSPE was significantly younger than that for controls who had had measles. Persons with SSPE were less likely to have received measles vaccine than were playmate or hospital controls. There were no differences with regard to the average age at vaccination, having received more than one measles vaccination, or having received measles vaccine after natural measles. Although measles vaccine may rarely predispose a child to develop SSPE, the overall impact of vaccination has been to prevent SSPE by preventing natural measles. No significant differences were observed between cases and controls for infections other than measles, or for vaccines other than measles vaccine. Previous epidemiologic studies have noted significant geographic clustering of SSPE and higher rates in children living in rural areas. These findings suggest that environmental factors other than measles are important in the pathogenesis of SSPE. In this study, children with SSPE were more likely to have suffered a serious head injury and to have come from larger families and more crowded homes than control children. Persons with SSPE were significantly more likely to have close exposure to birds (p less than 0.001) and to swine (p less than 0.05) than were control persons. No differences between cases and controls were found for exposure to other animals. These data suggest that some infectious agent(s), transmitted from birds to man, may have contributed to the development of SSPE in predisposed individuals. A variety of other factors were investigated and found not to correlate with SSPE. These included birth weight, breastfeeding, maternal age at birth, nutritional status, source of drinking water, development, and allergic or atopic disorders.

Illness after influenza vaccination reported through a nationwide surveillance system, 1976-1977.

In 1976, the Center for Disease Control coordinated nationwide surveillance for illnesses after influenza vaccination as part of an effort to vaccinate the nation against influenza A/New Jersey/76. For the 48,161,019 persons vaccinated in 1976, a total of 4733 reports of illness were received which included reports of 223 deaths. When Guillain-Barré syndrome was reported in vaccine recipients, an investigation was begun to examine this possible association. Other than the Guillain-Barré syndrome and rare cases of anaphylaxis, no serious illnesses were causally associated with influenza vaccination by this type of surveillance. Widespread underreporting of illness and death in the passive phase of this surveillance system, however, impaired the ability to draw conclusions about reactions to vaccine from the reports of illness received.

Guillain-Barre syndrome following vaccination in the National Influenza Immunization Program, United States, 1976--1977.

Because of an increase in the number of reports of Guillian-Barre syndrome (GBS) following A/New Jersey influenza vaccination, the National Influenza Immunization Program was suspended December 16, 1976 and nationwide surveillance for GBS was begun. This surveillance uncovered a total of 1098 patients with onset of GBS from October 1, 1976, to January 31, 1977, from all 50 states, District of Columbia, and Puerto Rico. A total of 532 patients had recently received an A/New Jersey influenza vaccination prior to their onset of GBS (vaccinated cases), and 15 patients received a vaccination after their onset of GBS. Five hundred forty-three patients had not been recently vaccinated with A/New Jersey influenza vaccine and the vaccination status for 8 was unknown. Epidemiologic evidence indicated that many cases of GBS were related to vaccination. When compared to the unvaccinated population, the vaccinated population had a significantly elevated attack rate in every adult age group. The estimated attributable risk of vaccine-related GBS in the adult population was just under one case per 100,000 vaccinations. The period of increased risk was concentrated primarily within the 5-week period after vaccination, although it lasted for approximately 9 or 10 weeks.

Epidemiology of subacute sclerosing panencephalitis.

The Subacute Sclerosing Panencephalitis Registry has compiled data from 453 instances of SSPE occurring in the United States from 1960 through 1976. The mean annual incidence during this period was 3.5 per 10 million persons under 20 years of age, 2.3 times higher for males than females, and 4.0 times higher for whites than blacks. Although the long-term pattern of incidence is unknown, the incidence of reported SSPE declined dramatically from 1970 to 1976. There are marked geographic variations of SSPE activity within the United States and also a higher incidence for children from farms (9.4 per 10 million persons under 20) compared with children from other rural domiciles (3.7 per 10 million), suburban children (2.9 per 10 million), and inner-city children (1.6 per 10 million). Available epidemiologic evidence suggests that some extrinsic factor, unrelated to measles or measles vaccine, is important in the pathogenesis of the disease.

Rubella immunization. Persistence of antibody four years after a large-scale field trial.

A long-term comparative field trial of three live, attenuated rubella vaccines (HPV-77 DE-5, HPV-77 DK-12, and Cendehill) was initiated in 1969 on the islands of Kauai and Hawaii in the state of Hawaii. Rubella hemagglutination-inhibition (HI) tests on prevaccination serum specimens from 7,931 children in the two study areas indicated an overall susceptibility to rubella of nearly 70%. The rates of seroconversion of 5,153 seronegative subjects to HPV-77 DE-5, HPV-77 DK-12, and Cendehill vaccine were 97.5%, 99.9%, and 99.8%, respectively. Over the subsequent four-year follow-up period, during which time natural exposure to rubella was minimal, the percent decline of geometric mean titers did not vary substantially among the three vaccine groups and measured about twofold for all three. A total of only 28 vaccines (0.7%) who seroconverted to one of the vaccines in 1969 lost all measurable antibody by 1974. Measurable antibody persisted in more than 98% of all vaccinees over the four-year period. Reinfection, thought possibly to be an important factor in maintaining titers, did not occur frequently in the study population and could not be related to outbreaks of disease.

Risk of congenital abnormality after inadvertent rubella vaccination of pregnant women.

The risk to a fetus after rubella vaccination of its mother is unknown. The Center for Disease Control has compiled information from the pregnancies of 343 women inadvertently given rubella vaccine shortly before or after conception. The pregnancies of 145 women were terminated by therapeutic abortion, and rubella vaccine virus was recovered from the products of conception of nine women, including six of the 28 known to be seronegative to rubella at the time of vaccination. None of the 172 infants carried to term had either clinical or serologic evidence of rubella infection, including 38 infants of women known to be susceptible and 12 additional women estimated to be susceptible at the time of rubella vaccination. On the basis of the binomial distribution, the maximum risk of fetal infection after maternal rubella vaccination is between 5 and 10 per cent. The actual risk is probably less.

Simultaneous administration of smallpox, measles, yellow fever, and diphtheria-pertussis-tetanus antigens to Nigerian children.

Children receiving smallpox, measles, and yellow fever vaccines simultaneously at separate sites responded adequately to all three vaccines. In those children, 9 months of age and older, who received these three vaccines in addition to diphtheria-pertussis-tetanus vaccine, there was a decrease in measles seroconversion rates from 89% to 70%. Possible interactions between live and killed vaccines should be considered when the administration of multiple antigens is planned.

Assessment of vaccination coverage, vaccination scar rates, and smallpox scarring in five areas of West Africa.

In 1966, nineteen countries of West and Central Africa began a regional smallpox eradication and measles control programme in cooperation with the World Health Organization. This paper summarizes sample survey data collected to assess the results of the programme in Northern Nigeria (Sokoto and Katsina Provinces), Western Nigeria, Niger, Dahomey, and Togo. These data indicate that the programme, which used mass vaccination campaigns based on a collecting-point strategy, was generally successful in reaching a high proportion of the population. Analysis of vaccination coverage and vaccination scar rates by age underlined the importance to the programme of newborn children who accumulate rapidly following the mass campaign. Of all persons without vaccination scars at the time of the surveys, 34.4% were under 5 years of age; in the absence of a maintenance programme, this figure would rise to 40% after 1 year.

Mass vaccination programs in developing countries.

PIP: Immunization programs have been demonstrated to be efficient and relatively inexpensive methods of disease prevention in both developed and developing countries. This article reviews the historical development of mass immunization campaigns, sets forth practical considerations in initiating such campaigns, and gives examples of contemporary mass immunization programs in developing countries--smallpox eradication and measles control in West and Central Africa and the global smallpox eradication program. Within the next few years, an increasing number of vaccination programs are expected to administer 6 or more antigens simultaneously. Preliminary studies in West Africa have confirmed the safety, efficacy, and acceptance of such an approach. Much of the cost of mass immunization campaigns involves the logistics of transporting vaccination teams to a village, so the maximum number of antigens should be delivered at one time to capitalize on this effort. There has been no evidence that the simultaneous administration of several live virus vaccines leads to an increase in complication rates. Jet injectors are now being developed that should be more economical as well as more readily adaptable to a multiple antigen campaign. Finally, improvements in vaccine potency offer the possibility that single injections of vaccines such as tetanus toxoid may result in adequate immunity.^ieng