Korean researchers identify how a 3rd dose of coronavirus vaccine prevents mutant infections

Korean researchers have identified the principle of how the third dose of the Covid-19 vaccine protects against infection with various virus variants.

The researchers said Tuesday that their findings were published in Nature Communications.

Professor Park Wan-beom of the Department of Infectious Diseases at Seoul National University Hospital, Professor Emeritus Oh Myoung-don of Seoul National University College of Medicine, Professor Chung Jun-ho of the Department of Biochemistry at the same college, Professor Kwon Sung-hoon of Seoul National University School of Electrical and Computer Engineering, and Dr. Kim Seung-taek of the Institut Pasteur Korea conducted the study jointly.

The team found that the third dose of the Covid-19 vaccine induces increased somatic cell hypermutation, which broadens the specificity of Covid-19 antibodies and enables them to respond to the wild-type virus and different variants.

Studies have shown that the third dose of the original Covid-19 vaccine is effective in preventing infection with Omicron variants. However, how antibodies are produced after multiple doses in immune cells that have never been exposed to the Omicron variant has not been identified.

Therefore, the researchers collected blood from 41 three-dose recipients of Pfizer's mRNA vaccine six times - once before the first dose, once before the second dose, three times before the third dose, and once after the third dose - and used next-generation sequencing (NGS) to track changes in Covid-19 antibodies.

The results showed a significant increase in somatic hypermutations in antibodies formed after Covid-19 vaccination. Somatic mutations occur in the structure of genes at antigen-binding sites. Antibodies with somatic hypermutations can bind to multiple antigens, allowing them to respond to different variations.

As the number of vaccine doses increased, so did the number of viruses against which Covid-19 antibodies responded. After the second dose, the antibodies could respond to major variants such as alpha-beta-gamma, and after the third dose, they could respond to sub-omicron variants.

"Somatic hypermutation induced by multiple vaccine doses broadens antibody specificity to viral antigens," the researchers said. "These changes are key to the mechanisms that respond to omicron variant infections."

The team added that these findings may help guide vaccination strategies to prevent infection in future pandemics.