The research, taken from the CLARITY study and published in GUT, found that 865 people given the Pfizer/BioNTech or the Oxford/AZ COVID-19 vaccine and treated with infliximab (Remicade) had significantly lower concentrations of antibodies when compared to 428 people on an alternative treatment, vedolizumab (Entyvio). Infliximab is prescribed to around two million people worldwide.