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Yellow fever control in Cameroon: where are we now and where are we going?

Wiysonge CS, Nomo E, Mawo J, Ofal J, Mimbouga J, Ticha J, Ndumbe PM - BMC Med (2008)

Bottom Line: In both districts, a total of 60,083 people (representing 88.2% of the 68,103 targeted) were vaccinated.In both the reactive and preventive SIAs, the mean wastage rates for vaccines and injection material were less than 5% and there was no report of a serious adverse event following immunisation.In order to sustain these initial successes, the country will have to attain and sustain high routine vaccination coverage in each successive birth cohort in every district.

View Article: PubMed Central - HTML - PubMed

Affiliation: Central Technical Group, Expanded Programme on Immunisation, Ministry of Public Health, Yaoundé, Cameroon. charles.wiysonge@mrc.ac.za

ABSTRACT

Background: Cameroon is one of 12 African countries that bear most of the global burden of yellow fever. In 2002 the country developed a five-year strategic plan for yellow fever control, which included strategies for prevention as well as rapid detection and response to outbreaks when they occur. We have used data collected by the national Expanded Programme on Immunisation to assess the progress made and challenges faced during the first four years of implementing the plan.

Methods: In January 2003, case-based surveillance of suspected yellow fever cases was instituted in the whole country. A year later, yellow fever immunisation at nine months of age (the same age as routine measles immunisation) was introduced. Supplementary immunisation activities (SIAs), both preventive and in response to outbreaks, also formed an integral part of the yellow fever control plan. Each level of the national health system makes a synthesis of its activities and sends this to the next higher level at defined regular intervals; monthly for routine data and daily for SIAs.

Results: From 2004 to 2006 the national routine yellow fever vaccination coverage rose from 58.7% to 72.2%. In addition, the country achieved parity between yellow fever and measles vaccination coverage in 2005 and has since maintained this performance level. The number of suspected yellow fever cases in the country increased from 156 in 2003 to 859 in 2006, and the proportion of districts that reported at least one suspected yellow fever case per year increased from 31.4% to 68.2%, respectively. Blood specimens were collected from all suspected cases (within 14 days of onset of symptoms) and tested at a central laboratory for yellow fever IgM antibodies; leading to confirmation of yellow fever outbreaks in the health districts of Bafia, Méri and Ntui in 2003, Ngaoundéré Rural in 2004, Yoko in 2005 and Messamena in 2006. Owing to constraints in rapidly mobilising the necessary resources, reactive SIAs were only conducted in Bafia and Méri several months after confirmation of the outbreak. In both districts, a total of 60,083 people (representing 88.2% of the 68,103 targeted) were vaccinated. Owing to the same constraints, SIAs were not conducted promptly in response to the outbreaks in Ntui, Ngaoundéré Rural, Yoko and Messamena. However, these four and two other health districts at high risk of yellow fever outbreaks (i.e. Maroua Urban and Ngaoundéré Urban) conducted preventive SIAs in November 2006, vaccinating a total of 752,195 people (92.8% of target population). In both the reactive and preventive SIAs, the mean wastage rates for vaccines and injection material were less than 5% and there was no report of a serious adverse event following immunisation.

Conclusion: Amidst other competing health priorities, over the past four years Cameroon has successfully planned and implemented evidence-based strategies for preventing yellow fever outbreaks and for detecting and responding to the outbreaks when they occur. In order to sustain these initial successes, the country will have to attain and sustain high routine vaccination coverage in each successive birth cohort in every district. This would require fostering and sustaining high-level political commitment, improving the planning and monitoring of immunisation services at all levels, adequate community mobilisation, and efficient coordination of current and future immunisation partners.

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Districts that conducted mass yellow fever vaccination campaigns in Cameroon in November 2006. Ngdéré, Ngaoundéré; Rur, Rural; Urb, Urban.
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Figure 3: Districts that conducted mass yellow fever vaccination campaigns in Cameroon in November 2006. Ngdéré, Ngaoundéré; Rur, Rural; Urb, Urban.

Mentions: In 2004, 16 high-risk districts with an estimated population of 1,848,158 people aged six months and above were selected for mass preventive vaccination campaigns. Each of the 16 districts was considered high risk either because it had reported a yellow fever outbreak within the last two decades or it has a large urban population in close proximity to a district that has recently reported an outbreak. The first phase of the preventive campaigns took place from 13 to 22 November 2006 in six districts (Figure 3), with vaccines supplied free from the GAVI Alliance yellow fever vaccine stockpile. During these supplementary immunisation activities, particular emphasis was placed on maintaining the cold chain, ensuring safe injection practices and surveillance of adverse events following immunisation (AEFIs). Vaccinators and supervisors were trained to recognise and report all adverse events in vaccinated persons following immunisation, and forms for reporting these AEFIs were distributed to all vaccination posts and health centres. During the 10 days of the vaccination campaigns, 752,195 (92.8%) people were vaccinated by 247 vaccination teams. The wastage rate for vaccines was 4.6% and that for safety boxes was 0.9%. Medical incidents were reported in 13 persons who had received the yellow fever vaccine (nine cases of injection site pain and swelling in the Ngaoundéré Urban health district and four cases of skin rash in the Yoko health district). None of these AEFIs was serious (i.e. life-threatening or required hospitalisation) and each was well managed by local health staff. There was high-level political commitment to these preventive vaccination campaigns which were officially launched in the Messamena health district of the East Province by the national Minister of Public Health, in the presence of WHO and UNICEF country representatives and high-ranking administrative and political leaders of the province. Following the successful implementation of the supplementary immunisation activities in the six districts, Cameroon plans to re-assess the risk of yellow fever outbreaks in the country [23] in 2007 in order to update the list of high-risk districts for the second phase of the preventive supplementary immunisation activities scheduled for 2008.


Yellow fever control in Cameroon: where are we now and where are we going?

Wiysonge CS, Nomo E, Mawo J, Ofal J, Mimbouga J, Ticha J, Ndumbe PM - BMC Med (2008)

Districts that conducted mass yellow fever vaccination campaigns in Cameroon in November 2006. Ngdéré, Ngaoundéré; Rur, Rural; Urb, Urban.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2268705&req=5

Figure 3: Districts that conducted mass yellow fever vaccination campaigns in Cameroon in November 2006. Ngdéré, Ngaoundéré; Rur, Rural; Urb, Urban.
Mentions: In 2004, 16 high-risk districts with an estimated population of 1,848,158 people aged six months and above were selected for mass preventive vaccination campaigns. Each of the 16 districts was considered high risk either because it had reported a yellow fever outbreak within the last two decades or it has a large urban population in close proximity to a district that has recently reported an outbreak. The first phase of the preventive campaigns took place from 13 to 22 November 2006 in six districts (Figure 3), with vaccines supplied free from the GAVI Alliance yellow fever vaccine stockpile. During these supplementary immunisation activities, particular emphasis was placed on maintaining the cold chain, ensuring safe injection practices and surveillance of adverse events following immunisation (AEFIs). Vaccinators and supervisors were trained to recognise and report all adverse events in vaccinated persons following immunisation, and forms for reporting these AEFIs were distributed to all vaccination posts and health centres. During the 10 days of the vaccination campaigns, 752,195 (92.8%) people were vaccinated by 247 vaccination teams. The wastage rate for vaccines was 4.6% and that for safety boxes was 0.9%. Medical incidents were reported in 13 persons who had received the yellow fever vaccine (nine cases of injection site pain and swelling in the Ngaoundéré Urban health district and four cases of skin rash in the Yoko health district). None of these AEFIs was serious (i.e. life-threatening or required hospitalisation) and each was well managed by local health staff. There was high-level political commitment to these preventive vaccination campaigns which were officially launched in the Messamena health district of the East Province by the national Minister of Public Health, in the presence of WHO and UNICEF country representatives and high-ranking administrative and political leaders of the province. Following the successful implementation of the supplementary immunisation activities in the six districts, Cameroon plans to re-assess the risk of yellow fever outbreaks in the country [23] in 2007 in order to update the list of high-risk districts for the second phase of the preventive supplementary immunisation activities scheduled for 2008.

Bottom Line: In both districts, a total of 60,083 people (representing 88.2% of the 68,103 targeted) were vaccinated.In both the reactive and preventive SIAs, the mean wastage rates for vaccines and injection material were less than 5% and there was no report of a serious adverse event following immunisation.In order to sustain these initial successes, the country will have to attain and sustain high routine vaccination coverage in each successive birth cohort in every district.

View Article: PubMed Central - HTML - PubMed

Affiliation: Central Technical Group, Expanded Programme on Immunisation, Ministry of Public Health, Yaoundé, Cameroon. charles.wiysonge@mrc.ac.za

ABSTRACT

Background: Cameroon is one of 12 African countries that bear most of the global burden of yellow fever. In 2002 the country developed a five-year strategic plan for yellow fever control, which included strategies for prevention as well as rapid detection and response to outbreaks when they occur. We have used data collected by the national Expanded Programme on Immunisation to assess the progress made and challenges faced during the first four years of implementing the plan.

Methods: In January 2003, case-based surveillance of suspected yellow fever cases was instituted in the whole country. A year later, yellow fever immunisation at nine months of age (the same age as routine measles immunisation) was introduced. Supplementary immunisation activities (SIAs), both preventive and in response to outbreaks, also formed an integral part of the yellow fever control plan. Each level of the national health system makes a synthesis of its activities and sends this to the next higher level at defined regular intervals; monthly for routine data and daily for SIAs.

Results: From 2004 to 2006 the national routine yellow fever vaccination coverage rose from 58.7% to 72.2%. In addition, the country achieved parity between yellow fever and measles vaccination coverage in 2005 and has since maintained this performance level. The number of suspected yellow fever cases in the country increased from 156 in 2003 to 859 in 2006, and the proportion of districts that reported at least one suspected yellow fever case per year increased from 31.4% to 68.2%, respectively. Blood specimens were collected from all suspected cases (within 14 days of onset of symptoms) and tested at a central laboratory for yellow fever IgM antibodies; leading to confirmation of yellow fever outbreaks in the health districts of Bafia, Méri and Ntui in 2003, Ngaoundéré Rural in 2004, Yoko in 2005 and Messamena in 2006. Owing to constraints in rapidly mobilising the necessary resources, reactive SIAs were only conducted in Bafia and Méri several months after confirmation of the outbreak. In both districts, a total of 60,083 people (representing 88.2% of the 68,103 targeted) were vaccinated. Owing to the same constraints, SIAs were not conducted promptly in response to the outbreaks in Ntui, Ngaoundéré Rural, Yoko and Messamena. However, these four and two other health districts at high risk of yellow fever outbreaks (i.e. Maroua Urban and Ngaoundéré Urban) conducted preventive SIAs in November 2006, vaccinating a total of 752,195 people (92.8% of target population). In both the reactive and preventive SIAs, the mean wastage rates for vaccines and injection material were less than 5% and there was no report of a serious adverse event following immunisation.

Conclusion: Amidst other competing health priorities, over the past four years Cameroon has successfully planned and implemented evidence-based strategies for preventing yellow fever outbreaks and for detecting and responding to the outbreaks when they occur. In order to sustain these initial successes, the country will have to attain and sustain high routine vaccination coverage in each successive birth cohort in every district. This would require fostering and sustaining high-level political commitment, improving the planning and monitoring of immunisation services at all levels, adequate community mobilisation, and efficient coordination of current and future immunisation partners.

Show MeSH
Related in: MedlinePlus