loss of consciousness; nausea; vomiting; stopped breathing several times for multiple seconds and they described her to be gurgling when her pulse ox went down to 83%; Difficulty breathing; severe Headcahe; This is a spontaneous report received Support from a contactable nurse from Pfizer sponsored program via medical information team. This case pertains to patient 3 of 3. A 15-year-old female patient received bnt162b2 (PFIZER-BIONTEC COVID-19 VACCINE, Solution for injection, Lot Number: ER8727; Expiry Date: 31Jul2021), dose 2 via an unspecified route of administration on 17Jun2021 (at the age of 15-year-old) as a single for COVID-19 immunisation. The patient medical history and concomitant medications were not reported. The patient historical vaccine included bnt162b2 (PFIZER-BIONTEC COVID-19 VACCINE), dose 1 via an unspecified route of administration on an unspecified date as a single for COVID-19 immunisation and had no reaction. On 17Jun2021, after 15 minutes of observation, the patient had a severe headache, difficulty breathing, loss of consciousness and stopped breathing several times for multiple seconds and they described her to be gurgling when her pulse ox went down to 83%. On an unspecified date, the patient also had nausea and vomiting. The patient pulse ox (documented as provided by caller) went down to 83%, she had severe headache, nausea, vomiting and she was unconscious. When she was unconscious was when her pulse ox was 83% and she stopped breathing intermittently for 10 to 12 seconds at a time. Then she started breathing again but was not responsive after she received the epinephrine then her pulse ox steadily rose again but was not responsive. She was like this until EMS took her away. The reporter stated that the most severe case was for this particular patient. She had already been vaccinated and had already gone through the 15 minute observation. All these kids came in a bus together, but this patient was sitting in the vehicle after the observation when the guardian brought her back to the nurses saying that she was complaining of a severe headache and at that point she had difficulty breathing and lost consciousness. The nurses reported that it appeared that she stopped breathing several times for multiple seconds and they described her to be gurgling when her pulse ox went down to 83%. At that time they administered epi (epinephrine) and called EMS. Her pulse ox and her breathing improved after the administration of epi, however she remained unresponsive when she was on the way to the hospital with EMS. The patient was taken to the hospital and she did improve. This was the 2nd dose, she had the 1st dose and did not have a reaction to it. The seriousness of the events severe headache, difficulty breathing, loss of consciousness, stopped breathing several times for multiple seconds and they described her to be gurgling when her pulse ox went down to 83% was reported as medically significant. The reporter stated that it was very serious. This patient reaction was a little more intense than just an anxiety induced reaction. She says with a pulse ox of 83% if they had not intervened then this would of been life threatening. It is medically significant but if they had not intervened then it would have been life threatening especially when you're talking about gurgling and a pulse ox of 83%. The reporter tends to think that with that severe of a reaction, with the pulse ox that low and her being unresponsive, she believes that this was probably a true adverse event. Outcome of the events was reported as unknown.  The reported causality for the events severe headache, had difficulty breathing and lost consciousness, stopped breathing several times for multiple seconds and they described her to be gurgling when her pulse ox went down to 83% was reported as related.  Information on Lot/Batch number was available. Additional information has been requested.; Sender's Comments: Based on known drug safety profile, there is reasonable possibility of causal association between the events respiratory arrest, loss of consciousness, dyspnea and headache and the suspect drug.  The impact of this report on the benefit/risk profile of the Pfizer product is evaluated as part of Pfizer procedures for safety evaluation, including the review and analysis of aggregate data for adverse events. Any safety concern identified as part of this review, as well as any appropriate action in response, will be promptly notified to regulatory authorities, Ethics Committees, and Investigators, as appropriate.