Oculo-respiratory syndrome (ORS), a new influenza vaccine associated adverse event, was identified in 2000. The 2000 case definition (ORS-2000) required the presence of bilateral red eyes or respiratory symptoms or facial edema occurring between 2 and 24h following immunization and lasting <or=48 h. We compared clinical manifestations of cases outside these timelines. Cases were classified as ORS-early (onset <2 h after immunization), ORS-late (onset >24 h), ORS-persistors (duration >48 h).Overall, the distribution of symptoms was similar between ORS-2000 and other case categories. ORS-early and ORS-late had less ocular involvement, ORS-late and ORS-persistors had more cough and sore throat, ORS-early had more facial edema and ORS-late had less. In comparison to ORS-2000, ORS-early were younger whereas ORS-persistors and ORS-late were significantly older suggesting that clinical manifestations of ORS vary with age with a more rapid induction of symptoms in younger individuals and longer duration for older ones.