Pfizer and AZ Vaccine Antibodies Begin to Decrease 6 Weeks After Second Dose

In Less Than 3 Months, Antibody Levels Drop by 50% in Some Cases... Time to Prepare for the 'Booster Shot'

(Photo by Reuters Yonhap News)

[Asia Economy Senior Reporter Jinsoo Lee] Antibody levels were found to decrease six weeks after completing the second dose of AstraZeneca and Pfizer COVID-19 vaccines.

According to research conducted by the University College London (UCL), a research-focused comprehensive university in the UK, some vaccine recipients experienced up to a 50% reduction in antibody levels within less than three months after completing the second dose.

However, a decrease in antibodies does not necessarily mean increased vulnerability to COVID-19 infection. This is due to the so-called "immune memory response." This is an adaptive immune response that activates when a previously encountered antigen invades the body again, primarily involving T cells and B cells. Some T and B cells that form antibodies against the antigen remain as memory cells even after the antigen disappears. When encountering the same antigen again, they transmit relevant information to help the immune system rapidly produce a large amount of antibodies. Vaccination utilizes this immunological memory effect.

The researchers are concerned that a decrease in antibody levels might mean a reduction in vaccine effectiveness. Professor Rob Aldridge, an infectious disease epidemiologist at UCL, said, "It is urgent to determine when the protective effect of the vaccine begins to decline."

[Image source=Reuters Yonhap News]

The UK's National Health Service (NHS) has begun planning a "booster shot" program (an additional injection to enhance or prolong the vaccine's immune effect) for after September, considering the possibility of reduced immunity.

While UK authorities have emphasized that booster shots may not be necessary, government advisory panels believe preparations should be made.

This study analyzed blood samples from 552 individuals who completed their second dose, mostly aged in their 50s and 60s. The results were recently published in the online edition of the medical journal The Lancet.