Aim 1: Explore the mucosal inflammatory response in participants exposed to LAIV: Using self-procured nasal swabs in 75 participants with CF (30 previously vaccinated and 45 LAIV naïve) and 45 healthy siblings, the investigators aim to explore: (a) the inflammatory response profiles in patients with and without CF before and after LAIV and (b) if participants' inflammatory profiles differ whether they report respiratory deteriorations after LAIV or not. As viral infections were shown to induce cytokines production (IL-1b IL-6, TNFa and CXCL-8 [IL-8]) in nasal secretions, the expression of these 4 inflammatory markers will be profiled using a multiplex cytokine detection kit after LAIV in participants with and without CF. The inflammatory signatures will be compared in patients with/without CF and with/without respiratory deteriorations.