Measles Incidence Before and After Mass Vaccination Campaigns in Burkina Faso
TL;DR: Measles control strategies in Sahelian Africa must balance incomplete impact on virus circulation with cost of more aggressive strategies that include older age groups, according to data from Burkina Faso.
Abstract: Burkina Faso conducted mass measles vaccination campaigns among children aged 9 months to 4 years during December 1998 and December 1999. The 1998 campaign was limited to six cities and towns, while the 1999 campaign was nationwide. The last year of explosive measles activity in Burkina Faso was 1996. Measles surveillance data suggest that the 1998 urban campaigns did not significantly impact measles incidence. After the 1999 national campaign, the total case count decreased during 2000 and 2001. However, 68% of measles cases occurred among children aged 5 years or older who were not included in the mass vaccination strategy. During 2000 and 2001, areas with high measles incidence were characterized by low population density and presence of mobile and poor populations. Measles control strategies in Sahelian Africa must balance incomplete impact on virus circulation with cost of more aggressive strategies that include older age groups.
Citations
More filters
TL;DR: It is shown that measles epidemics in Niger are highly episodic, particularly in the capital Niamey, and how increased vaccine coverage, but still below the local elimination threshold, could lead to increasingly variable major outbreaks in highly seasonally forced contexts.
Abstract: Although vaccination has almost eliminated measles in parts of the world, the disease remains a major killer in some high birth rate countries of the Sahel. On the basis of measles dynamics for industrialized countries, high birth rate regions should experience regular annual epidemics. Here, however, we show that measles epidemics in Niger are highly episodic, particularly in the capital Niamey. Models demonstrate that this variability arises from powerful seasonality in transmission-generating high amplitude epidemics-within the chaotic domain of deterministic dynamics. In practice, this leads to frequent stochastic fadeouts, interspersed with irregular, large epidemics. A metapopulation model illustrates how increased vaccine coverage, but still below the local elimination threshold, could lead to increasingly variable major outbreaks in highly seasonally forced contexts. Such erratic dynamics emphasize the importance both of control strategies that address build-up of susceptible individuals and efforts to mitigate the impact of large outbreaks when they occur.
311 citations
TL;DR: Values for measles CFRs remain imprecise, resulting in continued uncertainty about the actual toll measles exacts, and the broad range of case and death definitions, study populations and geography highlight the complexities in extrapolating results for global public health planning.
Abstract: Background Global deaths from measles have decreased notably in past decades, due to both increases in immunization rates and decreases in measles case fatality ratios (CFRs). While some aspects of the reduction in measles mortality can be monitored through increases in immunization coverage, estimating the level of measles deaths (in absolute terms) is problematic, particularly since incidence-based methods of estimation rely on accurate measures of measles CFRs. These ratios vary widely by geographic and epidemiologic context and even within the same community from year-to-year. Methods To understand better the variations in CFRs, we reviewed community-based studies published between 1980 and 2008 reporting age-specific measles CFRs. Results The results of the search consistently document that measles CFRs are highest in unvaccinated children under age 5 years; in outbreaks; the lowest CFRs occur in vaccinated children regardless of setting. The broad range of case and death definitions, study populations and geography highlight the complexities in extrapolating results for global public health planning. Conclusions Values for measles CFRs remain imprecise, resulting in continued uncertainty about the actual toll measles exacts.
178 citations
TL;DR: It is found that intervening early (up to 60 days after the start of the epidemic) and expanding the age range to all children aged 6 months to 15 years may lead to a much larger reduction in the number of cases in a West African urban setting like Niamey.
Abstract: The current World Health Organization recommendations for response during measles epidemics focus on case management rather than outbreak response vaccination (ORV) campaigns, which may occur too l...
89 citations
Cites background from "Measles Incidence Before and After ..."
...Experience in many parts of the world has found measles vaccination campaigns across wide age ranges to be much more effective in preventing periodic measles outbreaks (Arudo et al. 2003; Kambire et al. 2003; Munyoro et al. 2003)....
[...]
TL;DR: Migration of children between Cote d'Ivoire and Burkina Faso played a major role in the failure of the SIA to interrupt measles transmission and synchronization of measles control activities should be a high priority in countries with regions where much migration occurs.
Abstract: BACKGROUND Shortly after a measles supplementary immunization activity (SIA) targeting children from 9 months to 14 years of age that achieved high coverage, Burkina Faso had a large, serologically confirmed measles outbreak. To investigate the causes of this first reported failure of a widely successful measles control strategy we conducted a case-control study. METHODS Serologically confirmed measles cases aged > or =9 months at the time of the SIA in 6 heavily affected districts were frequency matched on age to 3 controls recruited from people frequenting health centres in the same districts. RESULTS Between January and July 2002, 1287 measles cases were reported throughout Burkina Faso. Of the 707 cases that were serologically confirmed, 358 (51%) were from 9 months to 14 years of age and 265 (37%) were > or =15 years of age. Among cases and controls from 9 months to 14 years of age significant risk factors for measles were lack of measles vaccination and, in the unvaccinated, recent travel to Cote d'Ivoire. Of the recent measles cases in Cote d'Ivoire 54% were there when exposed to measles. Among adults, risk factors included non-vaccination and the lack of school attendance during childhood. Vaccine effectiveness was estimated to be 98%. CONCLUSIONS Migration of children between Cote d'Ivoire and Burkina Faso played a major role in the failure of the SIA to interrupt measles transmission. Synchronization of measles control activities should be a high priority in countries with regions where much migration occurs.
48 citations
TL;DR: The results emphasize the need for improved strategies to reduce missed opportunities for vaccination and achieve high vaccination coverage nationwide in order to prevent large measles outbreaks and to continue progress toward measles mortality reduction.
35 citations
References
More filters
TL;DR: In conclusion, laboratory diagnosis of measles based on IgM serology varies depending on the timing of specimen collection and the test used, and the case for the use of the IgM capture assay as the confirmatory test appears to be uncertain.
Abstract: As progress is made toward elimination of measles, the laboratory confirmation of measles becomes increasingly important However, both false-positive and false-negative results can occur with the routinely used indirect measles immunoglobulin M (IgM) serology tests The measles IgM capture assay is considered to be more specific, and therefore, its use is indicated for confirmatory testing, but its relative performance has not been fully assessed Four commercial indirect measles IgM serology test kits (the Behring, Clark, Gull, and PanBio assays) and a commercial IgM capture assay (the Light Diagnostics assay) were evaluated for their abilities to detect measles virus-specific IgM antibody with a total of 308 serum samples from patients involved in a measles outbreak and with confirmed cases of measles and 454 samples from subjects without measles The Centers for Disease Control and Prevention (CDC) IgM capture assay was also used in a part of the evaluation Among the indirect assays, the overall sensitivities ranged from 828% (Clark assay) to 886% (Behring assay) and specificity ranged from 866% (PanBio assay) to 996% (Gull assay) These rates were 922 and 866%, respectively, for the Light Diagnostics capture assay and 870 and 948%, respectively, for the CDC capture assay While the Light Diagnostics capture assay had the best detection rate (80%) with the acute-phase samples compared with those for the rest of the tests (CDC capture assay, 77%; Behring assay, 70%; Gull assay, 69%; PanBio assay, 58%; and Clark assay, 57%), all tests showed a significantly improved sensitivity in the range of 92% (Clark and PanBio assays) to 97% (Light Diagnostics and CDC capture assays) with the convalescent-phase samples, as expected The best seropositivity rates (in the range of 92 to 100%) were observed with samples collected 6 to 14 days after the onset of symptoms The Gull assay showed the highest positive predictive value (996%), followed by the Behring assay (978%) and the CDC capture assay (961%) Overall, the Gull and Behring assays were found to be as good as or better than the capture assays In conclusion, laboratory diagnosis of measles based on IgM serology varies depending on the timing of specimen collection and the test used, and the case for the use of the IgM capture assay as the confirmatory test appears to be uncertain
88 citations
TL;DR: A deeper epidemiological understanding of the mechanism, strengths and weaknesses of pulse vaccination will optimize the chances of success elsewhere in the world.
69 citations
"Measles Incidence Before and After ..." refers background in this paper
...In subsequent years an explosive large-scale outbreak, usually observed every 2 to 4 years in countries with less than 50% measles vaccine coverage [6], was averted, most likely as a result of the 1999 national mass vaccination campaign....
[...]
TL;DR: Country-specific activity and coverage data were used to estimate the childhood mortality impact and costs of integrating vitamin A supplements into immunization campaigns conducted in 1998 and 1999.
Abstract: Country-specific activity and coverage data were used to estimate the childhood mortality impact (deaths averted) and costs of integrating vitamin A supplements into immunization campaigns conducted in 1998 and 1999. More than 94 million doses of vitamin A were administered in 41 countries in 1998, helping to avert nearly 169,000 deaths. During 1999, delivery of more than 97 million doses in 50 countries helped avert an estimated 242,000 deaths. The estimated incremental cost per death averted was US$72 (range: 36-142) in 1998 and US$64 (range: 32-126) in 1999. The estimated average total cost of providing supplementation per death averted was US$310 (range: 157-609) in 1998 and US$276 (range: 139-540) in 1999. Costs per death averted varied by campaign, depending on the number and proportion of the child population reached, number of doses received per child, and child mortality rates.
48 citations
"Measles Incidence Before and After ..." refers background in this paper
...It may also reflect the impact of vitamin A supplements administered by the MOH during NIDs since 1998 [10]....
[...]
TL;DR: The mass campaign enabled a substantial increase in measles vaccine coverage to be made because it reached a high proportion of children who were difficult to reach through routine methods.
Abstract: OBJECTIVE: To assess the impact of the National Immunization Days (NIDs) on measles vaccine coverage in Burkina Faso in 1998. METHODS: During the week after the campaign, in which measles vaccine was offered to children aged 9-59 months in six cities regardless of vaccination history, a cluster survey was conducted in Ouagadougou and Bobo Dioulasso, the country’s two largest cities. Interviewers visited the parents of 1267 children aged up to 59 months and examined vaccination cards. We analysed the data using cluster sample methodology for the 1041 children who were aged 9-59 months. FINDINGS: A total of 604 (57%) children had received routine measles vaccination prior to the campaign, and 823 (79%) were vaccinated during the NIDs. Among those who had previously had a routine vaccination, 484 (81%) were revaccinated during the NIDs. Among those not previously vaccinated, 339 (78%) received one dose during the NIDs. After the campaign, 943 (91%) children had received at least one dose of measles vaccine. Better socioeconomic status was associated with a higher chance of having been vaccinated routinely, but it was not associated with NID coverage. CONCLUSION: The mass campaign enabled a substantial increase in measles vaccine coverage to be made because it reached a high proportion of children who were difficult to reach through routine methods.
35 citations
"Measles Incidence Before and After ..." refers background in this paper
...In the same 6 districts, the 1998 mass vaccination campaign permitted vaccination of 79% of children residing in urban areas (78% of the population of the 6 health districts of Ouagadougou and Bobo Dioulasso) [3]....
[...]
...In other areas with moderate incidence (e.g., the health regions of Bobo Dioulasso and Dedougou), more than 70% of cases tested positive for measles, confirming the existence of moderate measles transmission....
[...]
...Ouagadougou and Bobo Dioulasso are spread over 6 health districts, with an estimated 78% urban population....
[...]
...During 2000, after the 1999 national campaign, measles incidence was higher than in 1999 in the 6 districts of Ouagadougou and Bobo Dioulasso but was lower than during 1999 elsewhere in the country....
[...]
...In December 1998, during the second round of poliomyelitis NIDs, measles vaccination was offered to all children aged 9–59 months who resided in 2 cities (Ouagadougou and Bobo Dioulasso) and 4 towns (Kaya, Koudougou, Ouahigouya, and Tenkodogo)....
[...]
Journal Article•
TL;DR: More than half (57.9%) of the children under 10 years of age did not have detectable antibodies to measles, suggesting that transmission of the disease is low in this mobile population.
Abstract: A serological survey was conducted among Tuareg nomads to determine their level of immunity to measles. More than half (57.9%) of the children under 10 years of age did not have detectable antibodies to measles, suggesting that transmission of the disease is low in this mobile population. Mothers' reports of their children's history of measles were accurate (positive predictive value 93.9% for under-5-year-olds). Nomads are a reservoir of susceptible individuals who require immunization strategies adapted to their particular life-styles. These can be implemented at relatively low cost.
29 citations
"Measles Incidence Before and After ..." refers background in this paper
...Previous studies have demonstrated that large proportions of nomadic people who have not been vaccinated against measles remain susceptible to measles until adulthood [7]....
[...]