Measles outbreak in a northern Pakistani village: epidemiology and vaccine effectiveness

In the spring of 1990, local community health workers reported a measles outbreak in several partially vaccinated villages in the Punial Valley in northern Pakistan. The authors conducted an investigation in one of these villages to assess vaccine coverage and vaccine efficacy and to describe the patterns of measles outbreaks that prevailed in this community. The results of a survey of the entire village revealed two major gaps in vaccine coverage: the small minority Sunni community and children over 3 years of age. Vaccine efficacy was estimated to range from 73 to 90% but was markedly reduced in children who were vaccinated under 12 months of age. The occurrence of an outbreak in a community in which a relatively new vaccination program is primarily directed at younger children has been predicted by theoretical models of measles dynamics and is consistent with the experience of other vaccination programs in the developing world. These observations suggest that, in some areas of the developing world, the age groups targeted to receive measles vaccinations may need to be broadened to ensure adequate coverage to prevent recurrent outbreaks.

Measles epidemic in Romania, 1996-1998: assessment of vaccine effectiveness by case-control and cohort studies

A measles epidemic occurred in Romania with 32,915 cases and 21 deaths reported between November 1996 and June 1998, despite high vaccination coverage since the early 1980s. Most cases were unvaccinated children aged <2 years and vaccinated school-aged children. A case-control study among preschool children and a cohort study among primary-school children were conducted to estimate effectiveness of Romanian-produced measles vaccine, and to evaluate age at vaccination and waning immunity as risk factors for vaccine failure. Both studies indicated that measles vaccine was highly effective. One dose reduced the risk for measles by 89% (95% confidence interval (CI) 85, 91); two doses reduced the risk by 96% (95% CI 92, 98). Children vaccinated at <1 year of age were not at increased risk for measles compared with children vaccinated at > or =1 year. Waning immunity was not identified as a risk factor since vaccine effectiveness was similar for children vaccinated 6-8, 9-11, and 12-14 years in the past. Because specific groups were not at risk for vaccine failure, an immunization campaign that targets all school-aged children who lack two doses may be an effective strategy for preventing outbreaks. A mass campaign followed by increased first-dose coverage should provide the population immunity required to interrupt indigenous measles virus transmission in Romania.

Comparative efficacy of three measles vaccines in Indian children

A Comparative study of three types of measles vaccines was undertaken among 1005 children. Of these 527 were vaccinated with the Serum Institute of India (SII) vaccine, 230 with Schwarz (SC) and 248 were vaccinated with Edmonston-Zegreb (EZ) vaccine (imported from Zegreb). Though the majority of children reacted favourably with all the three vaccines (SII: 98.43%; SC: 93.40%; EZ: 93.0%) with a rise in titre, but the percentage of seroconversion was significantly higher with the SII vaccine (p < 0.01). The Schwarz and Edmonston Zagreb vaccines showed significantly less GM titre as compared with the other age group i.e. 9-12 months (p < 0.05). With Serum Institute of India (SII) vaccine the GM titres were almost similar in the different age groups. The overall GM titre obtained with the SII vaccine was significantly higher than the SC vaccine (p > 0.001) as well as the EZ vaccine (p > 0.001). It is of interest to note that among the infants, 22.5% children had measles antibody in them before vaccination.

From disease control to child health and development

The control of diarrhoeal diseases, acute respiratory infections and other childhood killers--such as measles, malaria and malnutrition--is now combined in WHO's Division of Child Health and Development. The need for integrated management of childhood illness is shown in its historical context.

Protecting the world's children: the story of WHO's immunization programme

Systematic immunization on a worldwide scale was not officially recognized as a practical possibility until 1974, when WHO launched its Expanded Programme on Immunization. Today, 80% of the world's children receive this form of protection against childhood diseases during their first year of life. Coverage can reach 90% by the year 2000, the effectiveness of the vaccines used is improving, and vaccines against additional diseases are being added to the programme.

Centers for Disease Control and Prevention (CDC). Progress toward elimination of measles from the Americas

In 1994, the Pan American Health Organization (PAHO) established the goal of eliminating measles from the Western Hemisphere by 2000. To reach this goal, PAHO developed a measles-elimination strategy that includes three vaccination components ("catch-up," "keep-up," and "follow-up") and integrated epidemiologic and laboratory surveillance. The aim of the strategy is to achieve and maintain high levels of measles immunity among infants and children and detect all chains of transmission of measles virus through careful surveillance. This report updates measles surveillance data through February 1998 and summarizes the impact of elimination strategies on measles in the Americas.

Comparison of AIK-C measles vaccine in infants at 6 months with Schwarz vaccine at 9 months: a randomized controlled trial in Ghana

In a randomized controlled trial in a measles endemic area, standard-dose (4.0 log10pfu) AIK-C measles vaccine administered at 6 months of age was compared to standard-dose Schwarz vaccine (3.7log10pfu) given at 9 months. Seroconversion rates at 3 and 6 months after immunization in the two groups were comparable and similar. The geometric mean titres achieved were, however, significantly higher in the Schwarz group (P < 0.05). No immediate serious side-effects were observed with either vaccine. We conclude that standard-dose AIK-C measles vaccine can be recommended for measles immunization in children below 9 months of age, especially in highly endemic and high-risk areas in developing countries.

Rehabilitation of the expanded programme on immunization in Sudan following a poliomyelitis outbreak

In 1993 a large outbreak of paralytic poliomyelitis occurred in Sudan as a result of an accumulation of large numbers of susceptible children that was accelerated by faltering immunization services. The extent of the outbreak led to the rapid rehabilitation of Sudan's Expanded Programme on Immunization (EPI); the government began financing vaccine purchase, operational aspects of EPI were decentralized, vaccine delivery was changed from a mobile to a fixed-site strategy, a solar cold chain network was installed, inservice training was resuscitated, and social mobilization was enhanced. National immunization days (NIDs) for poliomyelitis eradication were conducted throughout the country, including the southern states during a cease fire in areas of conflict. Measles immunization coverage was increased by offering measles vaccine during the second round of NIDs and subsequently through routine immunization services. Supplemental tetanus toxoid immunization of women of child-bearing age began in three provinces at high risk for neonatal tetanus. From 1994 to 1996 reported immunization coverage increased and the incidence of all EPI target diseases fell. Trends in coverage, disease incidence, financing, and the implementation of WHO-recommended disease-control strategies suggest that more sustainable immunization services have been re-established in Sudan.

Measles incidence, case fatality, and delayed mortality in children with or without vitamin A supplementation in rural Ghana

Data on measles incidence, acute case fatality, and delayed mortality were collected on 25,443 children aged 0-95 months during the course of a community-based, double-blind, placebo-controlled, randomized trial of vitamin A supplementation in rural, northern Ghana between 1989 and 1991. Measles vaccine coverage in these children was 48%. The overall estimated measles incidence rate was 24.3 per 1,000 child-years, and acute case fatality was 15.7%. There was not significantly increased mortality in survivors of the acute phase of measles compared with controls (rate ratio = 1.22, 95% confidence interval (CI) 0.65-2.30). Reported incidence rates and case fatality were higher in families with low paternal education, in the dry season, and in unvaccinated children, and case fatality was higher in malnourished children. There was no sex difference in incidence, but acute case fatality was somewhat higher in girls than boys (adjusted odds ratio = 1.3, 95% CI 0.9-2.1). Measles incidence was lower in vitamin A-supplemented groups (23.6 per 1,000 child-years) than in placebo groups (28.9 per 1,000 child-years), but this difference was not statistically significant (p = 0.33). Among 946 measles cases in clusters randomized to receive vitamin A or placebo, there was no marked difference in acute measles case fatality between vitamin A-supplemented and placebo groups (15.4% vs. 14.5%, respectively). The biologic effects of vitamin A supplemented on the subsequent clinical manifestations and severity of measles need further elucidation.

Centers for Disease Control and Prevention (CDC). Progress toward global measles control and elimination, 1990-1996

In 1989, the World Health Assembly resolved to reduce measles morbidity by 90% and measles mortality by 95% by 1995, compared with disease burden during the prevaccine era. By 1996, the estimated incidence and death rates for measles worldwide were reduced by 78% and 88%, respectively. In 1990, the World Summit for Children adopted a goal of vaccinating 90% of children against measles by 2000. However, routine measles vaccination coverage has remained relatively stable since 1990, and an estimated 1 million children continue to die from this preventable disease each year. During the 1990s, the widespread use of innovative measles-control strategies in the Region of the Americas and countries such as Mongolia, South Africa, and the United Kingdom demonstrated that high-level measles control and even interruption of transmission is feasible over large geographic areas. This report updates the status of measles control and elimination worldwide and includes disease surveillance and vaccination coverage data received by the World Health Organization (WHO) headquarters in Geneva, Switzerland, as of August 29, 1997. These findings indicate that, in some regions, substantial progress has been made to control and interrupt measles transmission; in others, measles continues to cause high morbidity and mortality because of failure to implement measles-control strategies.

Effect of vitamin A supplementation on measles vaccination in nine-month-old infants

OBJECTIVE

Childhood immunization programs have been suggested as an infrastructure to deliver vitamin A supplements to children in developing countries. The effects of giving vitamin A, a potent immune enhancer, with measles immunization to nine-month-old infants is unknown.

METHODS

A randomized, double-masked, placebo-controlled clinical trial of vitamin A, 100,000 IU at the time of standard titer Schwarz measles immunization was conducted with nine-month-old infants in Bogor District, West Java, Indonesia. Antibody titers to measles were measured at baseline and one and six months following immunization.

RESULTS

394 infants received measles immunization, and 37 infants (9.4%) had baseline antibody titers > 1:120, which is consistent with previous natural measles infection. Of the remaining infants, 98.8% seroconverted to measles, and 99.3% had titers consistent with protection against measles six months postimmunization. Seroconversion rates were similar in vitamin A and placebo treatment groups.

CONCLUSION

High dose vitamin A supplementation can be given without reducing seroconversion to standard titer Schwatz measles immunization in nine-month-old infants.

The impact of immunization control activities on measles outbreaks in middle and low income countries

BACKGROUND

The World Health Organization recommended strategy for responding to measles outbreaks in developing countries does not promote the use of immunization campaigns due to their high cost, disruptive nature and limited impact. Given the substantial morbidity and mortality associated with such outbreaks, a literature review was conducted as a basis for re-evaluating this policy.

METHODS

Reports of supplementary immunization activities that were performed to control measles outbreaks in middle or low income countries were identified. The impact of the immunization activities on the course of each outbreak was evaluated by examining the data provided.

RESULTS

Of 66 reports detailing a measles outbreak in a middle or low income country, 17 described supplementary immunization activities which included seven 'non-selective' immunization campaigns, three 'selective' campaigns and one use of an early 2-dose schedule. Eight of the reports commented on the impact of the response, five of which reported a reduction in outbreak morbidity. Only one of the reports, from an isolated island outbreak, provided sufficient data to support a possible reduction in outbreak-associated morbidity.

CONCLUSIONS

There are limited data on the impact of measles outbreak immunization activities from developing countries. The available data do not support a change in the WHO recommended strategy for conducting a limited, if any, immunization response to such outbreaks. Immunization strategies which aim to prevent outbreaks may be more effective than campaigns to interrupt transmission of an outbreak which has already begun.

Child mortality following standard, medium or high titre measles immunization in West Africa

BACKGROUND

The World Health Organization (WHO) recommended the use of high titre measles vaccine in 1989. Subsequent long term follow-up of several trials yielded results suggesting higher mortality among children inoculated with medium and high titre vaccines compared to standard titre vaccines, although none of the individual trials found significant differences in mortality.

METHODS

Long term survival after standard, medium and high titre measles vaccines has been investigated in a combined analysis of all West African trials with mortality data. In trials from Guinea-Bissau, The Gambia and Senegal, children received medium or high titre vaccines from 4 months of age and were compared to control groups recruited at the same time later receiving standard titre vaccine from 9 months of age. All children were followed up to at least 3 years old.

RESULTS

Combining trials of high titre vaccines showed higher mortality among the high titre group compared to the standard group: mortality ratio (MR) = 1.33 (95% CI : 1.02-1. 73). Mortality among recipients of medium titre vaccines was not different from that in the standard vaccine group, MR = 1.11 (95% CI: 0.54-2.27). In a combined analysis by sex, the adjusted mortality ratios comparing high titre vaccine with standard vaccine were 1.86 (95% CI : 1.28-2.70) for females and 0.91 (95% CI : 0.61-1.35) for males. The trials were not designed to study long term mortality. Adjustments for several possible sources of bias did not alter the results.

CONCLUSIONS

The combined analysis showed a decreased survival related to high titre measles vaccine compared with standard titre vaccines, though solely among females. As a result of these studies from West Africa and a study from Haiti, WHO has recommended that high titre measles vaccine no longer be used.

Integrated management of the sick child

Diarrhoea, pneumonia, measles, malaria and malnutrition account for more than 70% of deaths and health facility visits among children under 5 years of age in developing countries. A number of programmes in WHO and UNICEF have developed an approach to the integrated management of the sick child, which is being coordinated by WHO's Division for the Control of Diarrhoeal and Acute Respiratory Disease. Integrated clinical guidelines have been developed and a training course for health workers in outpatient (first level) health facilities has been completed. In addition to case management of these diseases, the course incorporates significant prevention of disease through promotion of breast-feeding, counselling to solve feeding problems, and immunization of sick children. Other materials to train and support health workers are also being developed: an inpatient case management training course, medical school curricular materials, a drug supply management course, and materials to support monitoring and reinforcement of skills after training. A planning guide for interventions to improve household management of childhood illness is also being developed. Since management of the sick child is a cost-effective health intervention, which has been estimated to have a large impact on the global burden of disease in developing countries, the completion of these materials and their wide implementation should have a substantial impact on child mortality.

Intradermal administration of measles vaccines

The aim of the study reported here was to determine if bifurcated needles or multiple puncture cylinders would prove suitable for administration of measles vaccines. Children 9 to 11 months old in São Paulo, Brazil, were assigned to receive either Biken-Cam 70 (5,000 TCID50/0.5 ml) or Edmonston-Zagreb (7,000 TCID50/0.5 ml) measles vaccines intradermally with a bifurcated needle or a multiple puncture cylinder. These devices are usually used to administer smallpox or BCG vaccine. The volume of vaccine inoculated was approximately 0.003 ml. Measles IgG antibodies were measured by enzyme-linked immunosorbent assay (ELISA) at the time of vaccination and 8 weeks later. The study participants were examined 14 days after inoculation for possible adverse reactions. Overall, the children's average age was 9.5 +/- 0.66 months at vaccination. None of the 45 recipients of Biken-Cam vaccine responded serologically. The 49 Edmonston-Zagreb vaccine recipients immunized with the multiple puncture cylinder had a somewhat higher serologic response rate (35%) and mean concentration of measles antibodies (323 mIU/ml) than those 51 who received the same vaccine administered with the bifurcated needle (26% and 291 mIU/ml, respectively). The rates of reported symptoms after vaccination did not differ significantly among the groups. Overall, the low serologic response rates following intradermal immunization with for devices tested in this study indicate that this route of administration is not suitable for routine administration of standard-titer vaccines.

Measles control in Kinshasa, Zaire improved with high coverage and use of medium titre Edmonston Zagreb vaccine at age 6 months

BACKGROUND

To improve measles control in Kinshasa, Zaire, a project to increase vaccine coverage was begun in 1988, and in 1989, the city vaccination programme changed measles vaccination policy from Schwartz vaccine at age 9 months to medium titre Edmonston Zagreb (EZ) vaccine at age 6 months. We report the impact of the programme on measles incidence and mortality.

METHODS

Data on vaccine coverage were obtained from cluster sample surveys conducted every 1-2 years and from routine reports of vaccine doses administered. Data on measles incidence and mortality were obtained from sentinel surveillance sites. The serological response to EZ measles vaccine was evaluated at a health centre in 1989 and in a community survey in 1990.

RESULTS

Measles vaccine coverage estimated in cluster surveys increased from 50% of the 1984 birth cohort to 89% of the 1989 birth cohort, accepting either a home-based record or a verbal history of vaccination. Reported measles incidence per 10,000 [corrected] population decreased by over 90%, from 37.5 in 1980 (early vaccination years) to 1.6 in 1991. There was a relative decrease in the proportion of cases aged < 9 months (32% of cases in 1986-1987 and 23% of cases in 1990-1991) and an increase in the proportion aged > 23 months (29% of cases in 1986-1987 and 43% in 1990-1991). According to ELISA assays, 74-76% of children seroresponded to EZ vaccine administered at age 6-7 months under routine programme conditions.

CONCLUSIONS

Measles can be controlled in urban areas, although it is difficult to determine how great a contribution vaccination at age 6 months makes over and above the achievement of high coverage.

Measles control in Maputo, Mozambique, using a single dose of Schwarz vaccine at age 9 months

In Maputo city, immunization is available at government health facilities, all contacts being used to vaccinate children. Door-to-door mobilization is conducted to identify eligible children and refer them for immunization. Card-documented measles vaccine coverage, estimated by community surveys, rose from 48% in 1982 to 86% in 1986 and 92% in 1992. The median age at measles vaccination was 10.2 months in 1986 and 9.2 months in 1992. The reported measles incidence rates per 100,000 population fell by 92% from 569 in 1977-78 (pre-vaccination) to 44 in 1990-92, and the reported inpatient measles mortality fell from 19.8 to 0.7 per 100,000. Among children whose age at measles onset was known, the proportion of reported measles cases in children under 9 months of age fell from 2162 (20.3% of 10,636 cases) in 1982-85 to 1695 (17.8% of 9501 cases) in 1986-92. The proportion of cases in children aged > or = 5 years increased from 15.2% to 32.8% in the corresponding periods. The global goals for measles control can be achieved by a single dose of Schwarz vaccine at 9 months of age.

Sex-specific differences in mortality after high-titre measles immunization in rural Senegal

Administration of high-titre measles vaccine (Edmonston-Zagreb (EZ) at > 10(5) plaque-forming units (PFU) per dose) before the age of 9 months has been recommended in areas with high measles mortality before the routine age of immunization after 9 months. The study compares the long-term survival after high-titre measles immunization at 5 months of age with that following routine immunization with standard-titre vaccine at 10 months of age. At 5 months of age the high-titre group received Edmonston-Zagreb (EZ-HT, 5 months) or Schwarz (SW-HT, 5 months) at titres > 10(5) PFU per dose, while the standard-titre group received placebo at 5 months of age and < 10(4) PFU per dose of Schwarz vaccine at 10 months (SW-std, 10 months). All the children were followed up to at least 36 months of age. The mortality ratio (MR) for infants in the EZ-HT, 5 months and SW-HT, 5 months groups was 1.32 (P = 0.089) and 1.45 (P = 0.092), respectively, which did not differ significantly from that of recipients of the SW-std, 10 months. The higher MR among recipients of the high-titre vaccines was due to the significantly lower survival among females compared with the females who received SW-std vaccine (EZ-HT, 5 months MR = 1.76, P = 0.013; SW-HT, 5 months MR = 2.14, P = 0.017). For children aged 5-10 months the high-titre measles vaccine did not increase mortality relative to unvaccinated children who had received placebo.