a sore arm; she gave undiluted 0.2mL doses of the vials instead of diluting the formulation before administration.; she gave undiluted 0.2mL doses of the vials instead of diluting the formulation before administration.; This is a spontaneous report received from contactable reporter(s) (Other HCP) from medical information team.  A 10 year-old female patient received bnt162b2 (BNT162B2), intramuscular, administered in deltoid left, administration date 26Jan2022 15:15 (Lot number: FL0007, Expiration Date: 28Feb2022) at the age of 10 years as dose 1, 0.2 ml single for covid-19 immunisation. The patient had no relevant medical history. There were no concomitant medications. The following information was reported: OVERDOSE (non-serious), PRODUCT PREPARATION ERROR (non-serious) all with onset 26Jan2022, outcome "recovered" and all described as "she gave undiluted 0.2mL doses of the vials instead of diluting the formulation before administration."; PAIN IN EXTREMITY (non-serious), outcome "unknown", described as "a sore arm". Therapeutic measures were not taken as a result of overdose, product preparation error.  Additional information: Caller states that inquiry is regarding the Pfizer Covid 19 Vaccine orange cap vials. Caller states that she gave undiluted 0.2mL doses of the vials instead of diluting the formulation before administration. Caller states that it was given to a total of 4 patients, 2 boys and 2 girls, 7-10 years of age, 2 of them took it as their 1st shot, while the remaining 2 took them as their 2nd shot. Caller states that she already informed parents of the children regarding medication error, and of the risk of possible increased side effects. Caller confirmed if she wanted any more data on revaccination. Reporter seriousness for gave undiluted dose of vials instead of diluted ones and gave 0.2mL doses of undiluted vials: Medically significant. NDC number of COVID-19 vaccine pediatric: 59267-1055-4. No Investigation Assessment. Caller gave undiluted dose of vials instead of diluted ones, and she gave 0.2 mL doses of undiluted vials. Seriousness: Caller says according to the research this was not serious, but as someone who made an error it is causing her a lot of angst and is very significant to her, it makes her want to throw up because she made a mistake, which she has been doing this almost two years and had not made this mistake, though for the pediatrics it hasn't been that long. There has been no treatment so far. Pharmacist prepared and gave undiluted pediatric Pfizer vaccine. reporter had been giving Pfizer Tris plus Moderna- no dilution needed. This patient her brother come early and was asked to get the vaccine ready. Mother was informed when and realized the error and called the next day to check on child and mom reports this fine no side effects other than a sore arm.  Thankfully no clinical consequences. On 16Feb2022 patient received second dose of BNT162B2 intramuscularly at left deltoid (lot number: FL8099) for covid-19 immunisation   Follow up(14Feb2022): This is a follow up-spontaneous report from a same contactable nurse. This nurse reported for 10-year-old female patient in response to HCP letter sent via follow-up letter which included that:  Updated Information: For suspect product anatomical site of injection and route of administration added. Vaccination facility information added. New event added.  Follow-up attempts are completed. No further information is expected.; Sender's Comments: Linked Report(s) : US-PFIZER INC-202200149376 same reporter/drug/event, different patient.