Abstract
Sera were collected from 185 adults aged ≥ 70 years in London to evaluate the immune response to COVID-19 vaccines. A single dose of Pfizer/BioNtech vaccine resulted in > 94% seropositivity after 3 weeks in naïve individuals using the Roche Spike antibody assay, while two doses produced very high spike antibody levels, significantly higher than convalescent sera from mild-to-moderate PCR-confirmed adult cases. Our findings support the United Kingdom’s approach of prioritising the first dose and delaying the second dose of COVID-19 vaccine.
Highlights
Serum samples were tested with five different antibody assays: two for antibodies against the nucleoprotein (N) (SARS-CoV-2 IgG assay, Abbott, Illinois, United States and Elecsys Anti-SARS-CoV-2 total antibody assay, Roche Diagnostics, Basel, Switzerland [2,3]) to identify prior SARS-CoV-2 infection, and three for antibodies against the spike (S) protein to assess vaccine response (Roche immunoassay, Elecsys AntiSARS-CoV-2 S total antibody assay, Roche Diagnostics; an in-house receptor binding domain (RBD) indirect IgG ELISA [4]; and a lateral flow total antibody device (LFD), Fortress Diagnostics, Antrim, United Kingdom (UK)); the latter is currently used in the national Real-time Assessment of Community Transmission (REACT) study in the UK [5]
We present severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody responses in the first 185 adults aged 70–90 years, recruited from the end of January 2021 through North London primary care networks, who were tested ca 3 weeks either after their first or second Pfizer/BioNTech (Mainz, Germany) vaccine dose received as part of the national programme
Serum samples were tested with five different antibody assays: two for antibodies against the nucleoprotein (N) (SARS-CoV-2 IgG assay, Abbott, Illinois, United States and Elecsys Anti-SARS-CoV-2 total antibody assay, Roche Diagnostics, Basel, Switzerland [2,3]) to identify prior SARS-CoV-2 infection, and three for antibodies against the spike (S) protein to assess vaccine response (Roche immunoassay, Elecsys AntiSARS-CoV-2 S total antibody assay, Roche Diagnostics; an in-house receptor binding domain (RBD) indirect IgG ELISA [4]; and a lateral flow total antibody device (LFD), Fortress Diagnostics, Antrim, UK); the latter is currently used in the national Real-time Assessment of Community Transmission (REACT) study in the UK [5]
Summary
CI: confidence interval; N: nucleoprotein; RBD: receptor-binding domain assay; S: spike protein assay. Seropositivity with the Roche anti-N-antibody assays was interpreted as evidence of previous infection, while lack of antibody to nucleoprotein and presence of spike protein antibody indicated vaccine response. Antibody titres were significantly higher in those with prior SARS-CoV-2 infection (nucleoprotein antibody-positive) compared with previously uninfected individuals (twofold by RBD; 20-fold by Roche S for those aged 70–79 years, Figure 1 and Table 1). Of the 92 individuals tested 3 weeks after their first dose of Pfizer/BioNTech vaccine and with no evidence of previous SARS-CoV-2 infection, 71 (77%) were positive in the RBD assay, 71 (77%) by LFD and 87 (95%) in the Roche anti-S assay. Antibody levels after one vaccine dose in previously uninfected individuals were lower than convalescent sera using the RBD assay but similar when using the Roche anti-S assay (Figure 2 and Table 2). Did not significantly increase the geometric mean ratio (Table 2)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
