rash worsened; compromised immune system with the Multiple Myeloma/ getting the COVID-19 Vaccine; compromised immune system with the Multiple Myeloma/ getting the COVID-19 Vaccine; This is a spontaneous report from a contactable nurse for her husband. A 79-year-old male patient received the 1st dose of BNT162B2 (PFIZER-BIONTECH COVID-19 VACCINE, lot number: EL9261), via an unspecified route of administration at left arm on 26Jan2021 06:00 at single dose for covid-19 immunisation. Medical history included plasma cell myeloma from Oct2018, a compromised immune system with the Multiple Myeloma, rash from Dec2020 and ongoing. The patient had a diagnosis of multiple myeloma and had developed a slight rash on his left arm to lenalidomide (REVLIMID) before receiving the COVID vaccine, Benadryl was taken and after 3 days, it was gone.  It was only on his upper arms. She said a rash was a known side effect of the lenalidomide. The nurse giving his vaccine shot noticed his slight rash on his left arm. Concomitant medication included lenalidomide (REVLIMID) for 2.5 years for multiple myeloma in remission. The patient did not receive any other vaccines within 4 weeks prior to the COVID vaccine. The past drug included bortezomib (VELCADE), the patient was administered a chemo agent (bortezomib) at the oncology center every 2 weeks and the oncology center held off giving his chemo shot 2 weeks before he received his first COVID-19 Vaccine on 26Jan2021. The reporter said her husband would not restart the chemo shot until he sees his oncologist again. She clarified her husband has now been off the bortezomib for a month, as of 01Feb2021. The patient experienced rash worsened on 28Jan2021. By 28Jan2021 the rash had spread to his trunk and by 29Jan2021 to his back. She clarified his rash was a dry rash, with no blisters or oozing. Her first thought was to get an ointment or a spray. He has now been given prednisone instead of a dose pack and the rash was gone/ the rash cleared up almost immediately and will stop lenalidomide for a couple weeks and continue the round of prednisone. The doctor could alter his therapy as needed. On 04Feb2021, the rash was gone but her husband's doctor wants him to finish his prescribed course of Prednisone. She clarified the Prednisone (manufacturer: Actavis) 40 mg was started on 01Feb2021, the rash started fading fast. By the next day (Tuesday, 02Feb2021) the rash was really fading, and now (04Feb2021) the rash was totally not there. The doctor told her husband to take one Benadryl, and to continue taking the Benadryl if his rash itches. She said her husband's latest blood work didn't indicate anything.  She said her husband's labs were always off, but were normal for having Multiple Myeloma. Both doctors want to keep her husband off of the lenalidomide. Reporter seriousness was reported as medically significant . The patient was treated for Multiple Myeloma for the past 2-1/2 years. He had been doing well, and his cancer doctors approved of him getting the COVID-19 Vaccine. The oncologist wanted her to call Pfizer to see if she can find anything about the COVID-19 Vaccine and how it pertains to the lenalidomide and her husband's Multiple Myeloma. She said her husband was almost 80 years old and very active. She said her husband had been in remission Multiple Myeloma for a year and his blood work was fine. By the time her husband starts taking lenalidomide again, he would be off of lenalidomide for almost 4 weeks. She said her husband's oncologist said he was going to cut back her husband's lenalidomide milligram dose and change his lenalidomide frequency to every other day when he resumes the lenalidomide. The reporter checked her husband's blood pressure (130/76) on 29Jan2021, after his rash worsened. She saidnot require a visit to emergency room or physician office. The rash event outcome  his pulse was fine, and she tested his blood sugar and it was fine. She said he had no temperature, clarifying his temperature was 97.6. The event did was recovering. The drug result was reported as unrelated. The reporter and her husband's doctors don't think his rash has anything to do with the COVID-19 Vaccine. The patient asked if Pfizer can point her in any direction with regard to her husband's situation. She said she read the COVID-19 Vaccine is a dead virus, but wants to know if her husband should be cautious in getting the second COVID-19 Vaccine dose. She said her husband's doctors know that the rash was not precipitated by the COVID-19 Vaccine, but his rash did get worse after he got the first COVID-19 Vaccine dose. His second dose was due 16Feb2021. The reporter was wondering if she should delay the second dose of the vaccine, the vaccine would make the rash worse.; Sender's Comments: Based on the information currently provided, the rash worsened after 2 days following the vaccine use thus a contributory role of BNT162B2 might not be fully excluded towards the event onset.  Severe allergic reaction is the known risk for the product and Rash faded soon under Prednisone.  The underlying predisposing condition of allergies to multiple materials may put the patient at high risk of anaphylactic reactions. 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