serious vitamins b12 deficiency; this regulatory authority case was reported by a physician and describes the occurrence of anaemia vitamin b12 deficiency (serious vitamins b12 deficiency) in a 71-year-old male patient who received mrna-1273 (spikevax) for covid-19 vaccination. previously administered products included for product used for unknown indication: covid-19 vaccin on 01-jan-2021 and covid-19 vaccin on 01-feb-2021. past adverse reactions to the above products included no adverse event with covid-19 vaccin and covid-19 vaccin. on 22-dec-2021, the patient received dose of mrna-1273 (spikevax) (unknown route) 1 dosage form. on 24-dec-2021, the patient experienced anaemia vitamin b12 deficiency (serious vitamins b12 deficiency) (seriousness criterion medically significant). at the time of the report, anaemia vitamin b12 deficiency (serious vitamins b12 deficiency) was resolving. for mrna-1273 (spikevax) (unknown), the reporter did not provide any causality assessments. no concomitant medication was given. no treatment medication was given. company comment: this case concerns a 71-year-old male patient with no medical history provided, who experienced serious unexpected event of anaemia vitamin b12 deficiency two days after the administration of the mrna-1273 vaccine. the dose of the mrna-1273 vaccine was not clearly stated in the source document, and administration of an unspecified covid-19 vaccine was reported as historical vaccine, therefore, this dose of the mrna-1273 vaccine was most likely the third vaccination. at the time of this report, the event was resolving, however, no details were provided regarding the clinical course of the reported event. the patient's elderly age remains a major confounding factor for the event. the benefit-risk relationship of the mrna-1273 vaccine is not affected by this report. event seriousness assessed as per regulatory authority reporting.; sender's comments: this case concerns a 71-year-old male patient with no medical history provided, who experienced serious unexpected event of anaemia vitamin b12 deficiency two days after the administration of the mrna-1273 vaccine. the dose of the mrna-1273 vaccine was not clearly stated in the source document, and administration of an unspecified covid-19 vaccine was reported as historical vaccine, therefore, this dose of the mrna-1273 vaccine was most likely the third vaccination. at the time of this report, the event was resolving, however, no details were provided regarding the clinical course of the reported event. the patient's elderly age remains a major confounding factor for the event. the benefit-risk relationship of the mrna-1273 vaccine is not affected by this report. event seriousness assessed as per regulatory authority reporting