This literature-non-study case was reported in a literature article and describes the occurrence of AUTOIMMUNE THYROIDITIS (Hashimoto's Thyroiditis) in a 21-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below. LITERATURE REFERENCE: Immune response to SARS-CoV-2 Vaccine and following breakthrough Omicron infection in an autoimmune patient with Hashimoto's thyroiditis, pernicious anemia, and chronic atrophic autoimmune gastritis: A case report. Vaccines (RA). 2022;10(3):450. The patient's past medical history included SARS-CoV-2 infection (first infected with SARS-CoV-2 in November 2020 when the Alpha variant was predominant. Patient had severe symptoms for 6 days but was not hospitalized) in November 2020. On 06-Feb-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On 06-Mar-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 10-Aug-2021, the patient experienced AUTOIMMUNE THYROIDITIS (Hashimoto's Thyroiditis) (seriousness criterion medically significant). On 29-Sep-2021, the patient experienced PERNICIOUS ANAEMIA (Pernicious Anemia) and CHRONIC GASTRITIS (Chronic Atrophic Autoimmune Gastritis). On 28-Dec-2021, the patient experienced COVID-19 (Breakthrough infection with the Omicron variant). On an unknown date, the patient experienced DRUG INEFFECTIVE (Lack of drug effect) and VACCINATION COMPLICATION (Moderate reaction). The patient was treated with LEVOTHYROXINE at a dose of 25 microgram and DULOXETINE at a dose of 20 milligram. At the time of the report, AUTOIMMUNE THYROIDITIS (Hashimoto's Thyroiditis), PERNICIOUS ANAEMIA (Pernicious Anemia), COVID-19 (Breakthrough infection with the Omicron variant), VACCINATION COMPLICATION (Moderate reaction) and CHRONIC GASTRITIS (Chronic Atrophic Autoimmune Gastritis) outcome was unknown and DRUG INEFFECTIVE (Lack of drug effect) had resolved. DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On 01-Jan-2022, Polymerase chain reaction: positive (Positive) tested PCR-positive for SARS-CoV-2 Omicron. On an unknown date, Polymerase chain reaction: negative (Negative) A second blood sample was obtained two weeks post Omicron infection PCR-negative. For mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown), the reporter considered AUTOIMMUNE THYROIDITIS (Hashimoto's Thyroiditis), PERNICIOUS ANAEMIA (Pernicious Anemia), COVID-19 (Breakthrough infection with the Omicron variant), DRUG INEFFECTIVE (Lack of drug effect), VACCINATION COMPLICATION (Moderate reaction) and CHRONIC GASTRITIS (Chronic Atrophic Autoimmune Gastritis) to be related. Company comment: This Literature non-study case concerns a 21-year-old, female patient with reported medical history of prior COVID-19, who experienced the unexpected, serious (medically significant) AESI of Autoimmune thyroiditis, unexpected, serious (medically significant) event of hypothyroidism, unexpected non-serious AESI of COVID-19 (SARS-CoV-2 Omicron variant infection). The events Autoimmune Thyroiditis and Hypothyroidism occurred approximately 5 months and 4 days after the receiving the second dose of mRNA 1273. the event COVID-19 (SARS-CoV-2 Omicron variant infection) occurred approximately 9 months and 26 days after the second dose of mRNA 1273. Drug ineffective was also reported in this case. It should be noted that the patient had pernicious anaemia and chronic atrophic autoimmune gastritis after completing the primary series of mRNA 1273. The patient is not on any immunosuppressant medication at the time of vaccination and COVID-19 infection. The patient was tested for neutralizing antibodies post-infection which showed enhanced titers for multiple COVID-19 variants, compared to pre-infection status, including presence of neutralization of omicron. Treatment details were not reported in the case. The Omicron surge during the COVID-19 pandemic remains a confounder for the event COVID-19. The benefit-risk relationship of mRNA-1273 is not affected by this report. Most recent FOLLOW-UP information incorporated above includes: On 07-Apr-2022: Follow up received by safety on 08-Apr-2022 has Email with full text article received from team and contains significant information. Reporter details, Page number, Laboratory data, Product information and Event details updated.; Reporter's Comments: No concomitant medication were  provided by reporter. The patient was exposed again to SARS-CoV-2 on 27 December 2021, with symptoms starting on 28 December 2021, and tested PCR-positive for SARS-CoV-2 Omicron on 1 January 2022. Her symptoms included fever, body aches, fatigue, loss of appetite, cough, difficulty breathing, headaches, rhinitis, and nausea. The most severe symptoms were resolved after 6 days without hospitalization, but low oxygen levels with lingering symptoms persisted for two weeks. The patient was exposed again to SARS-CoV-2 on 27 December 2021, with symptoms started on 28 December 2021 and tested PCR positive for SARS-CoV-2 Omicron on 01 January 2021. A blood sample was collected from this individual on 3 November 2021, 8 months post second vaccination and prior to Omicron exposure. A second blood sample was obtained two weeks post Omicron infection PCR-negative. Sender's Comments: This Literature non-study case concerns a 21-year-old, female patient with reported medical history of prior COVID-19, who experienced the unexpected, serious (medically significant) AESI of Autoimmune thyroiditis,  unexpected, serious (medically significant) event of hypothyroidism, unexpected non-serious AESI of COVID-19 (SARS-CoV-2 Omicron variant infection). The events Autoimmune Thyroiditis and Hypothyroidism occurred approximately 5 months and 4 days after the receiving the second dose of mRNA 1273. the event COVID-19 (SARS-CoV-2 Omicron variant infection) occurred approximately 9 months and 26 days after the second dose of mRNA 1273. Drug ineffective was also reported in this case. It should be noted that the patient had pernicious anaemia and chronic atrophic autoimmune gastritis after completing the primary series of mRNA 1273. The patient is not on any immunosuppressant medication at the time of vaccination and COVID-19 infection. The patient was tested for neutralizing antibodies post-infection which showed enhanced titers for multiple COVID-19 variants, compared to pre-infection status, including presence of neutralization of omicron. Treatment details were not reported in the case. The Omicron surge during the COVID-19 pandemic remains a confounder for the event COVID-19. The benefit-risk relationship of mRNA-1273 is not affected by this report.