Vaccination site warmth/Induration, redness, warmth at injection site; Second injection lump injections site/Lump at injection site; Vaccination site induration/Induration, redness, warmth at injection site; Second injection red injection site/Induration, redness, warmth at injection site; Second injection subcutaneous/administered Covid vaccine subcutaneously; Half or more of the vaccine dripped down my arm; Half or more of the vaccine dripped down my arm/Topical exposure to vaccine; This spontaneous case was reported by a physician (subsequently medically confirmed) and describes the occurrence of INCORRECT ROUTE OF PRODUCT ADMINISTRATION (Second injection subcutaneous/administered Covid vaccine subcutaneously), ACCIDENTAL UNDERDOSE (Half or more of the vaccine dripped down my arm), EXPOSURE VIA SKIN CONTACT (Half or more of the vaccine dripped down my arm/Topical exposure to vaccine), VACCINATION SITE WARMTH (Vaccination site warmth/Induration, redness, warmth at injection site) and VACCINATION SITE MASS (Second injection lump injections site/Lump at injection site) in a 63-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 041L20A and 041L20A) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     No Medical History information was reported.   On 07-Jan-2021 at 4:00 PM, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. On 04-Feb-2021 at 1:00 PM, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Subcutaneous) dosage was changed to 1 dosage form. On 04-Feb-2021, the patient experienced INCORRECT ROUTE OF PRODUCT ADMINISTRATION (Second injection subcutaneous/administered Covid vaccine subcutaneously), ACCIDENTAL UNDERDOSE (Half or more of the vaccine dripped down my arm) and EXPOSURE VIA SKIN CONTACT (Half or more of the vaccine dripped down my arm/Topical exposure to vaccine). On an unknown date, the patient experienced VACCINATION SITE WARMTH (Vaccination site warmth/Induration, redness, warmth at injection site), VACCINATION SITE MASS (Second injection lump injections site/Lump at injection site), VACCINATION SITE INDURATION (Vaccination site induration/Induration, redness, warmth at injection site) and VACCINATION SITE ERYTHEMA (Second injection red injection site/Induration, redness, warmth at injection site). On 04-Feb-2021, INCORRECT ROUTE OF PRODUCT ADMINISTRATION (Second injection subcutaneous/administered Covid vaccine subcutaneously), ACCIDENTAL UNDERDOSE (Half or more of the vaccine dripped down my arm) and EXPOSURE VIA SKIN CONTACT (Half or more of the vaccine dripped down my arm/Topical exposure to vaccine) had resolved. At the time of the report, VACCINATION SITE WARMTH (Vaccination site warmth/Induration, redness, warmth at injection site), VACCINATION SITE INDURATION (Vaccination site induration/Induration, redness, warmth at injection site) and VACCINATION SITE ERYTHEMA (Second injection red injection site/Induration, redness, warmth at injection site) had resolved and VACCINATION SITE MASS (Second injection lump injections site/Lump at injection site) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On 05-Mar-2021, SARS-CoV-2 antibody test: positive (Positive) Positive (greater than or equal to 1.00S/CO) Antibodies to novel coronavirus SARS-CoV-2 detected..     For mRNA-1273 (Moderna COVID-19 Vaccine) (Subcutaneous), the reporter considered VACCINATION SITE WARMTH (Vaccination site warmth/Induration, redness, warmth at injection site), VACCINATION SITE INDURATION (Vaccination site induration/Induration, redness, warmth at injection site) and VACCINATION SITE ERYTHEMA (Second injection red injection site/Induration, redness, warmth at injection site) to be related. No further causality assessments were provided for INCORRECT ROUTE OF PRODUCT ADMINISTRATION (Second injection subcutaneous/administered Covid vaccine subcutaneously), ACCIDENTAL UNDERDOSE (Half or more of the vaccine dripped down my arm), EXPOSURE VIA SKIN CONTACT (Half or more of the vaccine dripped down my arm/Topical exposure to vaccine) and VACCINATION SITE MASS (Second injection lump injections site/Lump at injection site).    There were no concomitant medications. Treatment information was not reported.  The patient reported that a medical assistant administered the Covid vaccine subcutaneously and not intramuscularly (IM). Half or more of the vaccine dripped down her arm. She experienced redness, warmth and an indurated area at the vaccination site. IgG antibodies were checked (one month after the second dose) and were positive but the patient questioned how long they will last given that she didn't get the full second dose. The patient will recheck her antibodies in three months.   Upon internal review on 24-May-2021, the events of INAPPROPRIATE ROUTE OF VACCINATION (second injection subcutaneous), ACCIDENTAL UNDERDOSE (Half the dose leaked out of the arm), VACCINATION SITE LUMP (second injection lump injections site), VACCINATION SITE WARMTH (vaccination site warmth), VACCINATION SITE INDURATION (vaccination site induration), VACCINATION SITE ERYTHEMA (second injection red injection site) have been captured in case #MOD-2021-139207.   This case was linked to MOD-2021-011899 (Patient Link).   Most recent FOLLOW-UP information incorporated above includes: On 19-Mar-2021: Patient demographics updated. Events of induration, redness and warmth at injection site updated with outcome now recovered. Causality updated. Lab data added.