Longitudinal measurement of human immune responses to SARS-CoV-2 vaccines through serum immunoglobulins

Abstract Introduction The novel SARS-CoV-2 (COVID-19) vaccines generate antibodies to the viral spike protein. The mRNA vaccines Moderna Inc. and Pfizer-BioNTech and adenovirus vaccine Johnson & Johnson (J&J) work through generation of humoral immune responses, particularly immunoglobulin G (IgG) and immunoglobulin M (IgM) antibodies. We assessed IgG and IgM response in vaccinated patients longitudinally. Methods Blood was drawn from 106 subjects over the course of five time points ranging from pre-to post-vaccine inoculation of Moderna, Pfizer, or J&J. Blood was collected into serum separating tubes (SST). SSTs were spun at 1200rcf for 15 minutes; the serum was isolated and used for testing. Levels of IgG and IgM were measured in geometric mean titers, then analyzed through multiple t-tests across vaccines and demographics. Results Moderna vaccine recipients had a significantly higher IgG titer following vaccine inoculation (p < 0.0005 for Time Point 1, 2, 3, 4). No significant difference was observed across various demographics (age/gender) within vaccine types (p > 0.05). There was a steady decline in IgG and IgM levels after full inoculations, which were trending towards baseline levels. J&J recipients had little change in IgG and IgM after receiving the vaccine; however, significantly lower IgG than the Moderna (p = 0.0006) and Pfizer (p =0.0071). Conclusion With the use of IgG and IgM as immune response indicator, our data shows Moderna outperforming Pfizer at all Time Points following baseline testing, which suggests greater, longer-lasting immunity against COVID-19. With a low sample size for J&J (n = 5), it is unclear what implications the poor IgG response observed in this study indicates about the adenovirus vaccine.