A research letter published in the Lancet looks at levels of neutralising antibodies in the blood of Pfizer-BioNTech COVID-19 vaccine recipients that target SARS-CoV-2 variants of concern, including the Delta variant first discovered in India (B.1.617.2).
Prof Eleanor Riley, Professor of Immunology and Infectious Disease, University of Edinburgh, said:
“In this study, serum samples collected from people after one or two doses of the Pfizer BioNtech COVID-19 vaccine were tested for their ability to effectively neutralise the original (vaccine) strain of SARS-CoV-2 and four variants of concern, including the Delta (so-called India) variant. One strength of this study is that the serum samples were tested against each virus strain at the same time, allowing direct comparison of the data. It is clear that neutralising antibody concentrations against the Delta variant are lower than against the other strains, with the average concentration being at the lower end of the range seen for the vaccine strain. However, it is also the case that antibodies able to neutralise the Delta variant were identified in almost all samples, albeit at lower concentrations.