The effect of anti-SARS-CoV-2 monoclonal antibody, bamlanivimab, on endogenous immune response to COVID-19 vaccination

As the COVID-19 pandemic evolves, and vaccine rollout progresses, the availability and demand for monoclonal antibodies for the prevention and treatment of SARS-CoV-2 infection are also accelerating. This longitudinal serological study evaluated the magnitude and potency of the endogenous antibody response to COVID-19 vaccination in participants who first received a COVID-19 monoclonal antibody in a prevention study. Over the course of six months, serum samples were collected from the prevention population (nursing home residents and staff) enrolled in the BLAZE-2 clinical trial who had received either bamlanivimab (4200 mg) or placebo. In an unplanned component of this trial, a subset of these participants was subsequently fully vaccinated with two doses of either SpikeVax (Moderna) or Comirnaty (BioNTech/Pfizer) COVID-19 mRNA vaccines, as part of the US vaccination program. This post-hoc analysis assessed the immune response to vaccination for the subset of participants (N=135) without prior SARS-CoV-2 infection. Antibody titers and potency were assessed using three assays against SARS-CoV-2 proteins that bamlanivimab does not significantly bind to, thereby reflecting the endogenous antibody response. All bamlanivimab and placebo participants mounted a robust immune response to full COVID-19 vaccination, irrespective of age, risk-category and vaccine type, with any observed differences unlikely to be clinically meaningful. These findings are pertinent for informing public health policy with results that suggest a complementary role for COVID-19 monoclonal antibodies (mAbs) with COVID-19 vaccines and that the benefit of receiving COVID-19 vaccination at the earliest opportunity outweighs the minimal effect on the endogenous immune response due to prior prophylactic COVID-19 mAb infusion.