Genetic variants of SARS-CoV-2 have emerged over the course of the pandemic, threatening public health efforts to limit COVID-19 transmissions. Variants of concern are particularly worrying—these may be more transmissible, cause more severe disease symptoms, or evade currently available diagnostics, treatments, or vaccines.
Recently, researchers studying immune responses in people who received the Pfizer-BioNTech COVID vaccine observed that these individuals have much lower levels of antibodies against the Delta variant of SARS-CoV-2, as compared to other variants in circulation.
The Delta variant, first detected in India, has rapidly become the most dominant variant in the UK, and the efficacy of current COVID-19 vaccines to protect against this variant is still unknown. A series of 12 mutations in the spike protein differentiates the Delta variant from the virus first detected in Wuhan in late 2019.
This study by scientists at the Francis Crick Institute, the largest of its kind, sought to bridge this gap, investigating how vaccine-induced antibodies could neutralize emerging variants of concern in healthy adults. They tested the efficacy of neutralizing antibodies against five SARS-CoV-2 variants: the original strain, the D614G strain that was dominant in the European first wave in April 2020, and the Alpha, Beta, and Delta variants.
In individuals who had received both doses of the Pfizer-BioNTech vaccine, neutralizing antibody levels were five times lower against the Delta variant compared to those against the original strain (or the “blueprint” for current vaccines). These protective antibody responses were found to be even lower for those who had only received one dose of the vaccine.
"This virus will likely be around for some time to come, so we need to remain agile and vigilant,” said infectious disease specialist, Emma Wall. “Our study is designed to be responsive to shifts in the pandemic so that we can quickly provide evidence on changing risk and protection.”
"The most important thing is to ensure that vaccine protection remains high enough to keep as many people out of hospital as possible. And our results suggest that the best way to do this is to quickly deliver second doses and provide boosters to those whose immunity may not be high enough against these new variants," Wall added.