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BACKGROUNDMost individuals with prior COVID-19 disease manifest long-term protective immune responses against reinfection. Accordingly, we tested the hypothesis that humoral immune and reactogenicity responses to a SARS-CoV-2 mRNA vaccine differ in individuals with and without prior COVID-19 disease.METHODSHealth care workers (n = 61) with (n = 30) and without (n = 31) prior COVID-19 disease received two 30 μg doses of Pfizer BNT162b2 vaccine 3 weeks apart. Serum IgG antibody against the spike receptor-binding domain; serum neutralizing activity; and vaccine reactogenicity were assessed longitudinally every 2 weeks for 56 days after the first injection.RESULTSThe COVID-19 group manifested more rapid increases in spike IgG antibody and serum neutralizing activity after the first vaccine dose but showed little or no increase after the second dose compared with the infection-naive group. In fact, spike IgG was at its maximum level after the first dose in 36% of the COVID-19 group versus 0% of the infection-naive group. Peak IgG antibody levels were lower but appeared to fall more slowly in the COVID-19 group versus the infection-naive group. Finally, adverse systemic reactions, e.g., fever, headache, and malaise, were more frequent and lasted longer after both the first and second injection in the COVID-19 group than in the infection-naive group.CONCLUSIONIndividuals with prior COVID-19 disease demonstrate a robust, accelerated humoral immune response to the first dose but an attenuated response to the second dose of BNT162b2 vaccine compared with controls. The COVID-19 group also experienced greater reactogenicity. Humoral responses and reactogenicity to BNT162b2 differ qualitatively and quantitatively in individuals with prior COVID-19 disease compared with infection-naive individuals.FUNDINGThis work was supported by Temple University institutional funds.

BackgroundCurrent recommendations in the United States are that subjects with a previous history of COVID-19 disease receive the full 2 dose mRNA vaccine regimen. We tested the hypothesis that humoral immune responses and reactogenicity to a SARS-CoV-2 mRNA vaccine (BNT-162b2) differ qualitatively and quantitatively in subjects with prior SARS-CoV-2 infection versus infection-naïve subjects.MethodsHealth care workers (n=61) from a single academic institution with and without prior COVID-19 received two 30 µg doses of BNT162b2 vaccine 3 weeks apart. The COVID group (n=30) received vaccine approximately 7 months post infection. IgG antibody against the Spike receptor-binding domain (RBD), serum neutralizing activity and vaccine adverse reactions were assessed every 2 weeks for 56 days after the 1st injection. A longitudinal design and long study duration allowed the onset, maximum response and initial decay rate of Spike IgG antibody to be assessed in each subject. In addition, Spike IgG antibody levels are expressed as µg / mL to provide normal values for clinical decision making.FindingsSpike IgG responses were highly variable in both groups. However, the COVID group manifested rapid increases in Spike IgG antibody and serum neutralizing activity post 1st vaccine dose but little or no increase in Spike IgG or serum neutralizing activity after the 2nd dose. In fact, Spike IgG was maximum prior to the 2nd dose in 36% of the COVID group and 0% of controls. Peak IgG antibody was lower but appeared to fall more slowly in the COVID than in the control group. Finally, adverse systemic reactions e.g., fever, headache and malaise, after both the 1st and 2nd injection were more frequent and lasted longer in the COVID group than in the control group.ConclusionsHealth care workers with prior COVID-19 demonstrate a robust, accelerated humoral immune response to the 1st dose of the COVID-19 mRNA vaccine but attenuated response to the 2nd dose. They also experience greater reactogenicity than controls. Accordingly, subjects with prior COVID-19 may require only a single dose of vaccine.