severe dehydration; severe dehydration; thirst; could not sleep at night/ lack of sleep/ sleep interrupted; she had never heard him so anxious or disturbed that he could not get relief; she had never heard him so anxious or disturbed that he could not get relief; This is a spontaneous report received from a contactable consumer (medical technologist). A 19-year-old male patient (reporter's grandson) received BNT61B2 (PFIZER-BIONTECH COVID-19 VACCINE, lot number not reported), on 04Mar2021 (at the age of 19-year-old) as 1st dose, single dose for COVID-19 immunisation. Vaccine was not administered at military facility. The patient's medical history included diabetic (since 1 years old, he was diagnosed 1 week after getting the measles/mumps/rubella (MMR) vaccine), dehydrated and rapid heartbeat (patient once before got dehydrated on the Hiking Trail with a rapid heartbeat). The patient's concomitant medications included insulin for diabetic. The patient previously received measles/mumps/rubella (MMR) vaccine. The reporter (caller) mentioned that his grandson got the 1st dose of the vaccine on 04Mar2021. Several hours later (04Mar2021), he experienced severe dehydration and thirst and could not sleep at night. He was very very uncomfortable and usually did not complain regarding experiences. He was young and going to college and he was living on his own. He was also diabetic. She was worried about his safety regarding his intake of the 2nd dose, so she was wondering if this had been reported and for any recommendations before and after getting the 2nd dose. They were consulting with his endocrinologist and the nurse at the endocrinologist's clinic said that they recommend young diabetic people to drink tons of water when getting the vaccine. Caller mentioned that she herself got the Pfizer vaccine and had no problem with it. Caller mentioned that his Grandson was diabetic since 1 years old. He was diagnosed 1 week after getting the MMR vaccine. She also mentioned that his grandson just recently got in college and he was in the younger side of the spectrum. Caller is asking if there is any data that would include her grandson's conditions in the clinical trials. Caller stated she was calling about the Pfizer COVID Vaccine and stated her grandson who was the patient was the one who received his first dose of the vaccine on 04Mar2021 and that day he received the vaccine he told her that starting in the evening that same day (04Mar2021) she had never heard him so anxious or disturbed that he could not get relief and the adverse reaction he had was severe dehydration and thirst and it was giving him a fit. Caller stated she thinks he was probably 5'10'' in height or so and thinks he weighed around and between 175-180 pounds when she last asked him. Caller stated she was not an HCP but was a medical technologist calling on behalf of the patient and because she was a medical technologist, she is medically trained. Caller stated she had not been able to get back in touch with the patient to get all the details for the report before she called around to get help but also stated the patient had his sleep interrupted after the vaccine was administered and he could not sleep but thinks this is all resolved and must have been resolved but she couldn't say for certain how long that he could not sleep or how long the severe dehydration or thirst lasted but she can find out. Caller stated the patient had not yet had the 2nd dose of the Pfizer COVID Vaccine and had his patient card and stated she did not have the lot, expiry date or NDC for the first dose. Caller stated for the indication for which the patient was administered the COVID vaccine, she thought because the patient was diabetic and the HCP was very anxious for him to have defense against COVID and against all various types of virus or the school may have required it but she was not sure; states it was for the patient's own safety that his endocrinologist wanted him to have the vaccine. Caller stated that the patient did not have treatment for the reported event and he did not say to her that he had any treatment; caller stated she doubted the infirmary at his school is even open at the University and she did not know whether the patient would go to the infirmary or not. Caller stated she was calling to find out of there have been any reports or feedback on this reaction that the patient had or the adverse situation the patient had several hours after receiving the Pfizer COVID Vaccine; states specifically for the severe dehydration and thirst the patient experienced after being administered the Pfizer COVID Vaccine. Caller stated the patient was due to get his 2nd dose of the Pfizer COVID vaccine three weeks from 04Mar2021 and she was most anxious to find out what recommendations were given or if Pfizer heard complaints about other adverse events like the ones she was reporting on the patient. Caller stated the patient once before got dehydrated on the Hiking Trail with a rapid heartbeat and he was with his father at that time; no further details provided by the caller. Caller stated the patient reported this to her in conversation a day or so after he had the Pfizer COVID Vaccine and she is medically trained and it has been a long time since she used that medical training but the patient is diabetic since the age of 1 and he had good care and has been under the care of the hospital endocrinologist and his HCP since he was found to have diabetes and he uses his insulin pump very well. Caller stated the patient was off to college where very few were attending college and the patient had a very undesirable evening after the vaccine of lack of sleep and he was so thirsty and could not get hydrated and she knows dehydration is bad for anybody even if they aren't diabetic or if they have a life threatening type of illness but the patient was at school and did not have a family member to help take care of him and he was due for his 2nd shot three weeks from 04Mar2021. Caller stated she was trying to find out the best route for him to go report this and she told him to report the reaction to the HCP and to call the HCP who prescribed the vaccine; stated the patient's endocrinologist was not able to get in touch with the patient and he was not answering the phone; stated the patient is at college and he was on online courses. Caller stated she was very anxious to find out enough information about this and it is a concern to his treating physician and she was asking about recommendations about the patient not having his 2nd dose of the Pfizer COVID Vaccine; stated she spoke with the nurse that works with the endocrinologist for all of these 18 years they have cared for the patient. Caller states the HCP's nurse stated she had found that patients that receive the vaccine and have diabetes and are treated at the hospital they recommend that those patients drink tons and tons of water before having the vaccine because some types of people with diabetes have extreme thirst.  Caller stated she had no vaccine names, patient information or lot number or other information to provide on the patients that had the vaccine and have diabetes. Caller stated she spoke at the HCP office and stated there was no need for secrecy and HIPPA was not in Pfizer's domain; stated she cannot depend on the patient to look out for his own safety and she as a medical technologist used to give patients ordered glucose tolerance tests and she knew of the reactions that occurred with those patients and she did not want the patient to be stuck and wanted for him to do the smart thing of spending the night at home rather than drive back. Caller stated for those patients she administered glucose tests to she had no patient information or lot numbers or other information to provide and it was years ago before the Pfizer COVID vaccine came out. Caller stated she worked trying to get patient's diabetes under control at the University where she worked. Caller stated she already called and waited for organization but did not speak to anyone and left them a number to call her back a couple of days ago but she had not heard back; stated there were 18 people in the phone queue before her and she was hoping not to have to wait again. Caller stated her grandson probably does not had the time to wait on the phone being at college and he needed to do what he needed to do to be safe. Caller stated she had only spoken with the endocrinologist who treats the patient in his hometown and reported this information to the HCP's nurse and they are pretty good with follow up with patients. Caller stated she did not think the patient had other health issues and he actually had done extremely well on his insulin pump and had been on the insulin pump since about 3 years of age; stated she had no name of the insulin, had no lot numbers or further information. The events did not require emergency room or physician office visit. The outcome of the events was unknown.  No follow-up attempts are needed; information about lot/batch number cannot be obtained.