Insufficient Neutralizing Antibodies Against 'Major Variants' Even After Second Dose of Pfizer Vaccine

Antibody Response Levels Drop Further When Only First Dose of Vaccine Is Administered

The first batch of COVID-19 vaccines purchased by our government from the U.S. pharmaceutical company Moderna arrived at Incheon International Airport Cargo Terminal on the 1st. The Moderna vaccine is the fourth COVID-19 vaccine approved domestically, following AstraZeneca, Pfizer, and Janssen. Photo by Airport Press Photographers Group

It has been found that even after receiving two doses of the Pfizer-BioNTech COVID-19 vaccine, sufficient neutralizing antibodies against the 'major variants' of the coronavirus are not produced.

The results of this study, jointly conducted by the Francis Crick Institute and University College London Hospitals (UCLH) in the UK, were published on the 3rd (local time) as a 'Research letter' in the medical journal The Lancet.

This study was the largest to date investigating the neutralizing efficacy of vaccine-induced antibodies against the 'major variants' of the novel coronavirus. The research team tested the neutralizing efficacy of vaccine-induced antibodies against the original novel coronavirus first identified in Wuhan, China, and four variant coronaviruses.

In addition to the Alpha and Delta variants, the variant sub-lineage (D614G) that dominated Europe during the first wave in April last year and the Beta variant (B.1.351), first identified in South Africa, were included. The Alpha and Delta variants are WHO-designated names referring to novel coronavirus variant strains first discovered in the UK and India, respectively.

Comparative analysis of the concentration of 'neutralizing' antibodies, which block the virus's entry into cells, showed that even individuals who received two doses of the Pfizer vaccine had neutralizing antibody levels against the Delta variant that were only one-fifth of those against the original strain of the novel coronavirus when the same vaccine was applied.

Those who received only the first dose showed much lower antibody response levels. The decline in antibody levels with increasing age was consistent across all tested variants. No correlation was found with gender or body mass index (BMI).