The Meaning of SARS-CoV-2 Antibodies in a Patient with a Systemic Reaction to the mRNA-1273 SARS-CoV-2 Vaccine after Previous Natural Immunization

OBJECTIVES: There is limited experience regarding the meaning of SARS-CoV-2 antibodies after vaccination in patients with naturally acquired immunity. METHODS: We describe the case of a patient who received the first dose of the mRNA-1273 SARS-CoV-2 vaccine 6 months after his recovery from moderately severe COVID-19. RESULTS: Our patient had a positive nucleocapsid SARS-CoV-2 IgG/IgM titre with 78.7 multiple of cut-off indicating persistent humoral immune response 6 months after infection. After vaccination, he developed prolonged systemic symptoms (fever, fatigue, nausea, diarrhoea and myalgia) for a duration of 6 days. CONCLUSION: SARS-CoV-2 nucleocapsid antibodies provide information about naturally acquired immunity. For the assessment of immune response to vaccination, measurement of the SARS-CoV-2 spike antibody titre before and after vaccination is essential. Patients with naturally acquired immunity might develop a prolonged systemic reaction to the first dose of the mRNA-1273 SARS-CoV-2 vaccine. LEARNING POINTS: Patients with naturally acquired immunity might develop a prolonged systemic reaction after receiving an mRNA SARS-CoV-2 vaccine. Depending on the clinical situation of SARS-CoV-2 infection and/or vaccination, different antibody titres should be determined. The SARS-CoV-2 nucleocapsid antibodies provide information on whether or not natural immunization has taken place. To quantify the immune response induced by vaccination, the SARS-CoV-2 spike antibody titre before and after vaccination has to be measured.