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Active Monitoring of the Adverse Events Following Immunization (AEFI) with the Yellow Fever Vaccine during the Vaccination Campaign in Cameroon

Author(s): Z. Sando*1, F. N. G. A. Enoah2, J. Ateudjieu3, M. Demanou4, B. Anya5, M. Kobela6
Affiliation(s): 1Ministry of public health Yaounde-Cameroon, Gyneco-obstetric and paediatric hospital, Yaounde, 2Ministry of Public health, Gynaeco-obstetric and Paediatric Hospital, 3Ministry of Public health, Division of operational research, 4Ministry of public health Yaounde-Cameroon, Centre Pasteur, 5WHO-Cameroon, WHO, 6Ministry of Public health, Expanded program of immunization, Yaounde, Cameroon
Keywords: Yellow fever vaccine, Adverse events following immunization
Background:

In the perspective of putting in place of mass yellow fever vaccination campaigns, 12 African countries including Cameroon were targeted by the Global Alliance Vaccines and Immunization (GAVI) amongst the 34 countries of high risk of epidemic. The yellow fever vaccine is considered as one of the most efficient and sure vaccines and Adverse Events Following Immunization (AEFI) are rarely reported, the estimated risk being 1 to 3 cases per one million doses of vaccine administered. The vaccines used during the May 2009 mass vaccination campaign in the 62 health districts at high risk of yellow fever in Cameroon were supplied by Sanofi Pasteur Paris and Biomanguinhos in Brazil. This campaign involved a population of 7471062 persons, which constitutes 92% of the total population.

Methods:

A multidisciplinary expert committee, made up of 13 persons was formed. This committee was assigned the task of elaborating the documents and monitoring materials and to investigate AEFI with the yellow fever vaccine, to investigate and classify all cases of severe AEFI. The members of the committee were briefed by national and international experts with good experience on the monitoring of AEFI with the yellow fever vaccine. Likewise central and regional supervisors were briefed as well as the principal field actors.

Results/Conclusions:

Amongst the 356 cases of the AEFI with the yellow fever vaccine notified during the period of monitoring, we registered 312 minor cases, representing a proportion of 87.64% and 53 severe cases, representing a proportion of 14.88%. Amongst the severe AEFI, 09 cases were excluded (03 cases reclassified as minor and 06 cases lacked information). We therefore had a total of 50 cases of severe AEFI, which corresponds to the expected number. Amongst these severe cases were 05 deaths. 44 cases of severe AEFI were investigated excluding the 05 deaths. Amongst these, 03 were viscerotropic, 2 were cases of hypersensitivity, 1 neurotropic, and 38 programmatic errors or coincidence.In conclusion, the monitoring of AEFI during the yellow fever mass vaccination campaign of May 2009 in Cameroon led to the confirmation of the rarity of AEFI with the yellow fever vaccine in general, but showed that there is a probability of the occurrence of severe AEFI. Severe AEFI in Cameroon were mostly due to programmatic errors and coincidences.

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