The Reason the 3rd Dose Blocks Omicron Revealed [Reading Science]

US Research Team: "Neutralizing Antibody Levels Increased by 50% and Capable of Responding to Variants"

COVID-19 virus. Photo by Fusion Medical Animation

[Asia Economy Reporter Kim Bong-su] "There are numerous breakthrough infections, so do we really need a third dose?" A U.S. research team has answered that question. Messenger RNA (mRNA) COVID-19 vaccines such as Pfizer and Moderna were not specifically designed to target variants like Omicron. However, it has been confirmed that receiving a third dose significantly enhances both the quantity and performance of memory B cells, a type of immune cell, compared to the second dose.

According to the international academic journal Nature on the 22nd (local time), a research team from Rockefeller University recently published a study containing these findings. The team investigated why people who received three doses of mRNA vaccines show strong protection against severe disease despite reduced preventive effectiveness and frequent breakthrough infections. They confirmed that individuals with three doses possess memory B cells with much stronger functions and greater numbers than those with only two doses. Memory B cells remember the COVID-19 virus due to vaccination and are responsible for producing neutralizing antibodies that eliminate the virus upon actual invasion.

The research team particularly revealed that the third dose promotes an increase and functional enhancement of memory B cells specialized in producing neutralizing antibodies that interfere with the receptor-binding activity of the spike protein, which the COVID-19 virus uses to attach to cells. Those who received the third dose produce approximately 50% more neutralizing antibodies capable of neutralizing the Omicron variant compared to those with two doses. Additionally, the third dose provides memory B cells with a diverse repertoire, enabling them to rapidly produce antibodies that can also eliminate variants like Omicron.

The research team explained, "These findings may help understand why mRNA vaccines, despite not being specifically designed for variants such as Omicron, provide a certain level of protection and prevent severe disease when a third dose is administered."