‘Pfizer vaccine generates fewer antibodies against Delta variant’

NEW DELHI: US drugmaker Pfizer Inc.’s covid-19 vaccine generated fewer antibodies against the Delta variant of the novel coronavirus now prevalent in India compared to other variants, new research showed, a significant development as the country plans to include the vaccine in its mass immunization programme.

The variant, which was found first in India in October 2020, has now spread to 45 countries.

The study by the Francis Crick Institute and the National Institute for Health Research (NIHR) UCLH Biomedical Research Centre published in the medical journal Lancet also showed the antibody levels declined with increasing age and over time.

Scientists analysed antibodies in the blood of 250 healthy people who received either one or two doses of the Pfizer-BioNTech covid vaccine up to three months after their first dose. Using a new, highly accurate high throughput viral neutralization assay developed at the Crick Institute, they tested the ability of so-called ‘neutralizing antibodies’ to block the entry of the virus into cells against five different variants of SARS-CoV-2—the original strain first discovered in Wuhan, China, which was 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).

They then compared concentrations of these neutralizing antibodies among all variants. Scientists found that in people who had been fully 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.

Importantly, this antibody response was even less in people who had received just one dose. Among them, 79% had a quantifiable neutralizing 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, 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.

Among all variants, fewer antibodies were generated the older the individual receiving the vaccine. However, no correlation was observed for gender or body mass index. More work is underway to test neutralizing 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 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 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 said.

Although the scientists said lab 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 neutralizing antibody levels may still be associated with protection against covid, the research said.

“New variants occur naturally, and those that have an advantage will spread. Keeping track of these evolutionary changes is essential to retain control over the pandemic and return to normality,” said David L.V. 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 vaccine. This is the largest study published to date investigating vaccine-induced antibody neutralizing capacity against the newest variants of concern in healthy adults.