pain in the  arm; fever; a strong headache; covid IgG positive; Received Moderna Vaccine first dose and Pfizer Covid 19 Vaccine second dose; This is a spontaneous report from a contactable consumer or other non hcp (patient reported for herself).  A 53-year-old female patient received second dose of bnt162b2 (PFIZER-BIONTECH COVID-19 mRNA VACCINE, Solution for Injection, Batch/Lot Number: ER8729, Expiration Date: Jul2021), via an unspecified route of administration, administered in right arm on 09Apr2021 at 08:45 (at the age of 53-years-old) as dose 2 (initial Pfizer dose), single for COVID-19 immunization; covid-19 vaccine mrna (mrna 1273) (MODERNA COVID-19 VACCINE), via intramuscular route of administration in right arm on 12Mar2021 at 20:15 (Batch/Lot number 0011521A Rt) as dose 1, single for COVID-19 immunization. The patient medical history included shellfish allergy (patient does report an allergy to seafood, was asked and answered this twice and was made to fill out documents for vaccines in regard to this allergy). The patient's concomitant medications were none. The patient did not receive any other vaccine prior vaccinations within 4 weeks. Patient has not even received a Flu vaccine, put that on hold. On 09Apr2021 at 08:45, the patient received Moderna vaccine first dose and Pfizer Covid 19 vaccine second dose. Upon Follow-up (07Dec2021), it was reported that after the second dose (mixed), the patient had pain in the arm, fever and a strong headache that lasted for three and a half days and covid IgG positive on an unspecified date. Patient is a consumer reporting she received her second dose of the Covid 19 vaccine today, 09Apr2021, but the first dose patient received was the Moderna vaccine. Somehow the administering facility messed up and the caller received the Pfizer Covid 19 Vaccine today for the second dose. Patient's concerned is there something caller should do, steps caller should take, any symptoms patient should be aware of. Stated received the Pfizer Covid 19 Vaccine as patient's second dose today, almost four hours ago. HCP: Patient stated she does not have that information on hand with her, but she talked to her doctor this morning. Patient's doctor was the first call made. She has been provided different information and wanted to talk to Pfizer to confirm. Patient's second dose: given in the Right arm, patient is a lefty and decided to go with the right arm. Patient unable to provide lot number for Moderna Vaccine. Moderna Vaccine: Late afternoon 19:00 or 20:00, Pfizer Covid 19 Vaccine about 08:45 this morning. Patient stated both the Moderna Vaccine and the Pfizer Covid 19 Vaccine were administered at the same facility and this is why she doesn't understand how they messed up. The patient underwent lab tests which included SARS-CoV-2 antibody test: IgM Negative and IgG: Positive on 30Apr2021, SARS-CoV-2 test: Negative on 24Apr2021. The outcome of all the events was unknown.  No follow up attempts are needed. No further information is expected.  Follow-Up (26Oct2021): Follow-up attempts are completed. No further information is expected.  Follow-up (06Dec2021 and 13Dec2021): This is a spontaneous follow-up report received from the same contactable consumer. Updated information included: Concomitant drugs updated as None. Events (pain in the arm, fever and a strong headache and suspected COVID-19) added, Batch/ lot number for dose 1, vaccination facility address, relevant test added. Case closure added.  Follow-up attempts are completed. No further information is expected.