Avian infl uenza vaccination of poultry and passive case reporting, Egypt

We investigated the infl uence of a mass poultry vaccination campaign on passive surveillance of highly pathogenic avian infl uenza subtype (H5N1) outbreaks among poultry in Egypt. Passive reporting dropped during the campaign, although probability of infection remained unchanged. Future poultry vaccination campaigns should consider this negative impact on reporting for adapting surveillance strategies.