Pfizer Covid jab produces less antibodies against Delta variant: Lancet study | Key findings

Individuals fully vaccinated with the Pfizer-BioNTech vaccine are likely to have nearly six times reduced levels of neutralising antibodies against the coronavirus variant first detected in India, according to a new study published in The Lancet. The team, led by researchers from the Francis Crick Institute in the UK, determined neutralising antibodies in the blood of 250 healthy individuals, who had received either one or two doses of the Pfizer-BioNTech Covid-19 vaccine, against five SARS-CoV-2 strains.

Across all variants of concern, the researchers found lower levels of these antibodies with increasing age, while no correlation was observed for sex or body-mass index. They, however, also noted that the levels of antibodies alone do not predict vaccine efficacy against the variants and that prospective population studies are also needed.

The research paper was published on the backdrop of the UK’s decision to reduce the gap between two doses of vaccine to address the concerns about the spread of the B.1.617 variant, named by the World Health Organization (WHO) as ‘Delta’. The study supports the UK’s current vaccination plan since the researchers found that people are less likely to develop the level of neutralising antibodies against the Delta variant as high as those seen against B.1.1.7, or the Alpha variant, first found in Kent.

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Here are some of the key findings:

• Peak neutralising antibodies titres are significantly reduced against B.1.617.2 and B.1.351 (Beta variant) when compared against earlier variants.
• Single-dose recipients are likely to be less protected against Delta or Beta variants.
• It remains difficult to assess precisely to what extent the reduction in neutralising antibodies will impact vaccine efficacy and increase disease severity in a vaccinated population.
• Increased age and time since the second dose of Pfizer-BioNTech Covid-19 vaccine significantly correlate with decreased neutralising antibodies activity against Delta and Beta variants.
• Consequently, further booster immunisations to vulnerable people are more likely to be required to maintain the highest levels of neutralising antibodies in regions where Delta variant or other equally neutralising antibody-resistant strains become prevalent.