London: According to research published in The Lancet journal, people fully immunized with the Pfizer-BioNTech vaccine are expected to have more than five times lower levels of neutralizing antibodies against the Delta variant first identified in India compared to the original strain.
The research also shows that levels of these antibodies that are able to identify and fight the virus are lower with increasing age and that levels decrease over time, giving additional data in support of plans to deliver a booster dose to vulnerable people.
In the UK, it supports current plans to reduce the dose gap between vaccines since they found that after just one dose of the Pfizer-BioNTech vaccine, people are less likely to develop antibody levels against the B.1.617.2 variant as high as those seen against the previously dominant B.1.1.7 (Alpha) variant, first found in Kent.
A team, led by researchers from the Francis Crick Institute in the UK, recorded that levels of antibodies alone do not predict vaccine effectiveness and prospective population studies are also needed. Lower neutralizing antibody levels may still be correlated with protection against COVID-19, they said.
According to the study, it analyzed antibodies in the blood of 250 healthy people who received either one or two doses of the Pfizer-BioNTech Covid-19 vaccine, up to three months after their first dose. The researchers tested the efficacy of antibodies to block entry of the virus into cells, so-called ‘neutralizing antibodies’, against five different variants of SARS-CoV-2. And, they then compared concentrations of these neutralizing antibodies between all variants. Data from previous clinical studies suggest that higher antibody titers or concentrations are a good predictor of vaccine effectiveness and greater protection against COVID-19.
It was found by the researchers that in people who had been vaccinated with two doses of the Pfizer-BioNTech vaccine, levels of neutralizing antibodies were more than five times lower against the B.1.617.2 variant when compared to the original strain, upon which current vaccines are based. This antibody response was even lower in people who had only received one dose, they said.
After a single dose of Pfizer-BioNTech, 79 percent of people had a quantifiable neutralizing antibody response against the original strain, but this fell to 50 percent for B.1.1.7, 32 percent for B.1.617.2, and 25 percent for B.1.351 or Beta variant first identified in South Africa. While antibody levels declined with age against all variants, no correlation was observed for sex or body mass index (BMI).
Emma Wall, an Infectious Diseases consultant at University College London Hospitals NHS Foundation Trust (UCLH) said, “This virus will likely be around for some time to come, so we need to remain agile and vigilant.”.
“Our study is designed to be responsive to shifts in the pandemic so that we can quickly provide evidence on changing risk and protection,” Wall said.
The researchers remarked that the most important thing is to assure that vaccine protection remains high enough to keep as many people out of hospital as possible. As the study suggests that the best way to do this is to instantly deliver second doses and provide boosters to those whose immunity may not be high enough against these new variants, they said.
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