Measles vaccination coverage during poliomyelitis national immunization days in Burkina Faso, 1999

Measles outbreak in Burkina Faso, 2009: a case-control study to determine risk factors and estimate vaccine effectiveness

OBJECTIVE

We investigated a large measles outbreak that occurred in 2009 in Burkina Faso in order to describe the epidemic, assess risk factors associated with measles, and estimate measles vaccine effectiveness.

METHODS

We reviewed national surveillance and measles vaccine coverage data, and conducted a case-control study in three geographic areas. Case-patients were randomly selected from the national case-based measles surveillance database or, when a case-patient could not be traced, were persons in the same community who experienced an illness meeting the WHO measles clinical case definition. Controls were matched to the same age stratum (age 1-14 years or age 15-30 years) and community as case-patients. Risk factors were assessed using conditional logistic regression.

RESULTS

Lack of measles vaccination was the main risk factor for measles in all three geographic areas for children aged 1-14 years (adjusted matched odds ratio [aMOR] [95% confidence interval (CI)], 19.4 [2.4-155.9], 5.9 [1.6-21.5], and 6.4 [1.8-23.0] in Bogodogo, Zorgho, and Sahel, respectively) and persons aged 15-30 years (aMOR [95% CI], 3.2 [1.1-9.7], 19.7 [3.3-infinity], 8.0 [1.8-34.8] in Bogodogo, Zorgho, and Sahel, respectively). Among children aged 1-14 years, VE of any measles vaccination prior to 2009 was 94% (95% CI, 45-99%) in Bogodogo, 87% (95% CI, 37-97%) in Zorgho, and 84% (95% CI, 41-96%) in Sahel. Main reasons for not receiving measles vaccination were lack of knowledge about vaccination campaigns or need for measles vaccination and absence during vaccination outreach or campaign activities.

CONCLUSION

These 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.

Trends in immunization completion and disparities in the context of health reforms: the case study of Tanzania

Background

Of global concern is the decline in under five children mortality which has reversed in some countries in sub Saharan Africa (SSA) since the early 1990 s which could be due to disparities in access to preventive services including immunization. This paper is aimed at determining the trend in disparities in completion of immunization using Tanzania Demographic and Health Surveys (DHS).

Methods

DHS studies randomly selected representative households from all regions in Tanzania since 1980 s, is repeated every five years in the same enumeration areas. The last three data sets (1990, 1996 and 2004) were downloaded and analyzed using STATA 9.0. The analysis included all children of between 12-23 months who would have completed all vaccinations required at 12 months.

Results

Across the time periods 1990, 1996 to 2004/05 the percentage of children completing vaccination was similar (71.0% in 1990, 72.7% in 1996 and 72.3% in 2005). There was no disparity in completion of immunization with wealth strata in 1990 and 1996 (p > 0.05) but not 2004. In 2004/05 there was marked disparity as most poor experienced significant decline in immunization completion while the least poor had significant increase (p < 0.001). All three periods children from households whose head had low education were less likely to complete immunization (p < 0.01).

Conclusion

Equity that existed in 1990 and more pronounced in 1996 regressed to inequity in 2005, thus though at national level immunization coverage did not change, but at sub-group there was significant disparity associated with the changing contexts and reforms. To address sub-group disparities in immunization it is recommended to adopt strategies focused at governance and health system to reach all population groups and most poor.

Migration as a risk factor for measles after a mass vaccination campaign, Burkina Faso, 2002†

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.

Use of administrative data to estimate mass vaccination campaign coverage, Burkina Faso, 1999

Administrative coverage data are commonly used to assess coverage of mass vaccination campaigns. These estimates are obtained by dividing the number of doses administered by the number of children of eligible age, usually at the health district level. This study used data from a cluster survey conducted in each of the 53 Burkina Faso health districts immediately after 1999 the National Immunization Days to assess whether administrative estimates correlated with those obtained through survey and whether the former identified districts that achieved suboptimal coverage as measured by cluster survey. During the first round of the campaign there was no significant correlation between data obtained by either method. The correlation was only marginally better during the second round. Although useful to help plan the logistics of a campaign, administrative coverage data should be used with other evaluation techniques in order to determine the number of eligible children vaccinated during a mass campaign.

Measles incidence before and after mass vaccination campaigns in Burkina Faso

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.

Impact of nationwide measles vaccination campaign among children aged 9 months to 14 years, Zimbabwe, 1998-2001

Zimbabwe (population 11,365,000) introduced nationwide one-dose measles vaccination in 1981. This strategy reached 70%-80% of infants <1 year of age over the next two decades; in 1998, a nationwide supplemental immunization activity (SIA) targeting all children aged 9 months to 14 years achieved 93% coverage. Surveillance data were examined to determine the impact of these strategies. During 1985-1997, there were 8529-49,812 measles cases annually. After the SIA, laboratory confirmation of the first 5 outbreak cases and all sporadic cases was required. In 1999 and 2000, 1343 (88%) of 1534 suspected cases had adequate specimens submitted and 28 (2%) were measles IgM positive. In 2001, of 529 suspected cases, 513 (97%) had adequate specimens and only 7 (1%) were measles IgM positive. These data suggest that indigenous measles transmission in Zimbabwe has been interrupted and that high prevalence of human immunodeficiency virus seropositivity does not hinder vaccination-induced measles control. High vaccination coverage obtained through the routine health care system supplemented by periodic follow-up SIAs will be required to maintain low transmission levels.

The unfinished measles immunization agenda

Despite achieving and sustaining global measles vaccination coverage of about 80% over the past decade, worldwide measles remains the fifth leading cause of mortality among children aged <5 years. In May 2002, the United Nations Special Session on Children endorsed the goal of reducing measles deaths by half by 2005. Countries and World Health Organization (WHO) regions that adopted aggressive measles control or elimination strategies have shown excellent results. In 2001, countries in the Americas reported an all time low of 537 confirmed measles cases. Substantial progress in measles control has also been achieved in the WHO Western Pacific Region, in seven southern African countries, and in selected countries in WHO European, Eastern Mediterranean, and Southeast Asian regions. The ongoing measles disease burden and availability of safe and effective measles mortality reduction strategies make a compelling case to complete the unfinished agenda of measles immunization.