PremiumNEW DELHI: Pfizer-BioNTech's covid-19 vaccine elicits lower levels of antibodies against the SARS-CoV-2 Delta variant (B.1.617.2), first discovered in India, in comparison to other variants, said a research published in Lancet journal.
The research holds importance for India as the country plans to include Pfizer covid-19 jab in its vaccination program. B.1.617.2, prevalent in India, has already spread to over 45 countries.
Results from a study by Francis Crick Institute and the National Institute for Health Research (NIHR) UCLH Biomedical Research Centre, published on Thursday as a research letter in The Lancet showed that the antibody levels decline over time.
Scientists analysed 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. Using a new highly accurate high output viral neutralisation assay developed at the Crick, they tested the ability of 'neutralising antibodies' to block entry of the virus into cells.
They were tested against five different variants --SARS-CoV-2, the original strain first discovered in Wuhan, China; the dominant strain in Europe during the first wave in April 2020 (D614G); B.1.1.7, the variant first discovered in Kent, UK (Alpha); B.1.351, the variant first discovered in South Africa (Beta) and B.1.617.2, the newest variant of concern, first discovered in India (Delta).
The concentration of neutralising antibodies was compared between all variants. Scientists found that in people who had been fully vaccinated with two doses of the Pfizer-BioNTech, levels of neutralising antibodies were five times lower against the B.1.617.2 variant when compared to the original strain, upon which current vaccines are based.
Importantly, this antibody response was even lower in people who had only received one dose. After a single dose of Pfizer-BioNTech, 79% of people had a quantifiable neutralising antibody response against the original strain, but this fell to 50% for B.1.1.7, 32% for B.1.617.2, and 25% for B.1.351.
The researchers also 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 (Delta) variant as high as those seen against the previously dominant B.1.1.7 (Alpha) variant.
While antibody levels decreased with age against all variants, no correlation was observed for gender or BMI. More work is underway to test neutralising antibodies against these same variants in people who have been vaccinated with the Oxford/AstraZeneca vaccine.
"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," Emma Wall, UCLH Infectious Diseases consultant and Senior Clinical Research Fellow for the Legacy study, said.
“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," she added.
Although, scientists said laboratory results such as these are needed to provide a guide as to how the virus might be evolving to escape the first generation of vaccines, levels of antibodies alone do not predict vaccine effectiveness and prospective population studies are also needed. Lower neutralising antibody levels may still be associated with protection against covid-19, the research said.
"New variants occur naturally and those that have an advantage will spread. Keeping track of these evolutionary changes is essential for us to retain control over the pandemic and return to normality," said David LV Bauer, group leader of the Crick's RNA Virus Replication Laboratory and member of the G2P-UK National Virology Consortium.
Researchers have submitted their findings to the Genotype-to-Phenotype National Virology Consortium (G2P-UK), the New and Emerging Respiratory Virus Threats Advisory Group (NERVTAG) and the Joint Committee on Vaccination and Immunisation (JCVI), as evidence of the level of protection people might receive against the new variants after one dose and both doses of the Pfizer covid-19 vaccine. This is the largest study published to date investigating vaccine-induced antibody neutralising capacity against the newest variants of concern in healthy adults.
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