A report has been received from a literature article concerning a 3 year old, male patient. Patient was with cystic fibrosis (CF) diagnosed on newborn screening (sweat chloride 90mmol/L, F508del homozygous) attended routine follow-up in the CF clinic. He had had a wet cough for the previous 3 weeks. In addition to CF, he had previously been diagnosed with gastrooesophageal reflux (oesophageal pH < 4.0 for 13% of study at age 2 months) and an unsafe swallow with risk of aspiration on thin fluids (on videofluoroscopy at age 23 months). He had completed a 2 week course of Co-amoxiclav 400/57 5mL twice daily and then started a 2 week course of ciprofloxacin 250 mg twice daily in view of a previous growth of Pseudomonas aeruginosa at 14 months of age. He was not wheezing but his mother said that she could feel crackling in his chest. He was otherwise well, with no fever or coryzal symptoms. A cough swab taken at this clinic showed no bacterial growth. Three months prior to this he had similar symptoms, during which an induced sputum grew Haemophilus influenzae, which was ampicillin resistant and treated with a course of cefixime. Person stated that in summary, this preschool child with CF has ongoing symptoms despite appropriate empiric courses of antibiotics. At this point, the differential includes CF-related issues and coincident disease. In this particular child, issues unrelated to CF particularly include ongoing aspiration on syrup consistency fluids, but other causes of chronic cough, for example, TB and endobronchial foreign body must not be forgotten. It should also be remembered that a simple cold in a normal child might cause symptoms lasting more than 3 weeks. According to Clinical examination excluded common childhood causes for persistent cough such as tonsillitis or viral-induced wheeze. Proton pump inhibitor therapy was already maximal for his age, and he was not given an additional H2 blocker. ABPA markers were normal, with negative aspergillus lgG, Aspergillus fumigatus RAST 0.1 IU/ml and a total lgE of 25 IU/ml. Random blood glucose readings were 4.2 and 4.6 mmoL/L (75-83 mg/dl). In view of possible ongoing aspiration, he was referred again to the speech and language therapy team for a repeat assessment. He was reviewed after 4 weeks in outpatients by a consultant who again noted a wet cough, which occasionally had an added wheezing note. However, at that point, he had a runny nose. Another course of co-amoxiclav was given, with inhaled salbutamol for wheezing symptoms, and a videofluoroscopy arranged. That again showed a risk of aspiration with thin fluids, with a safe effective swallow on syrup-thick fluids. Cough swab at clinic again was negative. Person stated that after 4 weeks he reviewed him in clinic. He looked sleepy and not himself, with an ongoing cough, a hoarse voice and a respiratory rate of 48 breaths per minute while asleep. Chest radiograph showed bronchial wall thickening in the right lower zone and behind the heart. By that time he had been coughing for nearly 2 months, with no diagnosis. He was admitted for bronchoscopy and intravenous antibiotics. According to Bronchoscopy revealed anatomically normal airways but with friable inflamed mucosa and creamy yellow secretions. Cell differential demonstrated a neutrophilia (64%). Microbiological samples identified H. influenzae on bacterial culture, and a PCR assay of the lavage fluid, for nucleic acids from common respiratory viruses, was positive for influenza A RNA. He was treated with intravenous ceftazidime and tobramycin, oral oseltamivir and isolated from other inpatients. On subsequent discussion with his mother, we learnt he had received the FLUMIST vaccination (live attenuated influenza vaccine (LAIV)) 2 days prior to the bronchoscopy. To our knowledge, this is the first report of a positive bronchoalveolar lavage (Preferred Term: Bronchoalveolar lavage) sample in a child with CF who recently received the LAIV. It was a true-positive microbiological test in the context of what is essentially a clinically false-positive result; we initially attributed his cough to a prolonged viral chest exacerbation with influenza. There was an interaction with diagnosis (Preferred Term: Drug-disease interaction). Outcome of the events interaction with diagnosis and positive bronchoalveolar lavage was unknown. Author's comment: We report this case to avoid others making the same mistake. The lesson we learnt is to take a comprehensive vaccine history when taking microbiological samples and that in this era of live inhaled vaccines, a live attenuated vaccine might cause a false-positive result. The Centre for Disease Control guidelines advice that LAIV should not be administered until 48 hours after the cessation of antiviral drugs active against influenza and it is possible that we have attenuated our patient's immune response to the influenza vaccination. His wet cough has improved on thickened fluids and we have attributed the cough to his unsafe swallow. Investigations into the aetiology of this were ongoing. Report was considered to be serious with seriousness criteria of important medical event. Sender's Comments: This is a case of 3 year old male patient reported with drug disease interaction after receiving FLUMIST. It was reported that LAIV (Live attenuated influenza vaccine) was found in bronchoalveolar fluid after 48 hours of vaccination. Underlying cystic fibrosis, gastrooesophageal reflux, and an unsafe swallow with risk of aspiration on thin fluids along with concomitant use of oseltamivir and the fact that patient was vaccinated 2 days back could possibly explain drug disease interaction.