A team from the Basic and Translational Research of Tumor Immunology at Chongqing Medical University in southwestern China conducted mice laboratory experiments and found concerning results. If these findings are applicable to humans, it could raise serious concerns about the continued use of COVID-19 vaccine boosters.
In the West, a strategy of administering repetitive vaccine boosters has been adopted in response to the ongoing changes in the SARS-CoV-2 virus that have resulted in the emergence of variants with neutralization escape mutations. Chinese scientists have pointed out that there is limited knowledge regarding A) the level of protection offered by these vaccine boosters and B) any potential adverse effects associated with them.
The authors of the study used Balb/c mice models to compare the humoral and cellular immune response of an extended course of boosters from a recombinant receptor binding domain (RBD) vaccine to a conventional vaccination strategy.
According to the report, if individuals receive multiple vaccine boosters after the initial primary series, their RBD-specific antibody titers and serum neutralizing efficacy against both Delta and Omicron variants decrease significantly.
The report also highlights a significant reduction in CD4 and CD8 T cell activation, with higher expressions of PD-1 and LAG-3 in observed T cells. It is crucial to note these findings.
The authors state that using a RBD multi-booster vaccine strategy can reset the immune memory and promote adaptive immune tolerance. However, they also caution that there may be significant health risks if SARS-CoV-2 vaccine boosters are administered continuously.
Although the primary series of COVID-19 mRNA vaccines have been approved by the U.S. Food and Drug Administration, they do not have any long-term safety data. Additionally, three boosters have been authorized with limited data. It is unclear what the long-term safety effects of multiple boosters administered within a relatively short period of time (one or two years) will be.
The study titled “Extended SARS-CoV-2 RBD booster vaccination induces humoral and cellular immune tolerance in mice,” with corresponding authors Wang Wang and Ai-Shun Jin, suggests concerning results.
According to the authors, in a study conducted by Wang et al., it was found that 38 people who received a second booster of inactivated COVID-19 vaccine showed a similar decrease in humoral immunity.
Wang Wang and Ai-Shun Jin, who are both corresponding authors, conduct studies in the Laboratory of Basic and Translational Research of Tumor Immunology, which is affiliated with Chongqing Medical University. They have recently reported their findings.
Extended vaccination not only reduced the amount and effectiveness of antibodies against RBD in the serum, but also had a negative impact on long-term immunity by decreasing the number of B and Tfh cells in the spleen. Additionally, CD4+ and CD8+ T cells showed a decrease in functionality, and there was a decrease in memory T cells while expression of PD-1 and LAG-3 increased in subtype cells.
The study findings indicate that other researchers should pay attention to this evidence as it could significantly impact current COVID-19 vaccination plans. The authors suggest that using the same type of booster shots repeatedly may lead to immune tolerance issues. They caution against hasty optimization of the extended plan for SARS-CoV-2 booster vaccinations.
One suggestion to address the Omicron mutant is to consider changing from continuously administering the same vaccine to using a different approach, such as switching to a heterologous booster midway through.
The study authors recognized some limitations, such as the use of a rodent model instead of primates, which are more similar to humans. However, they noted that the Balb/c mice model has significant similarities with humans in their reaction to SARS-CoV-2 infections, although the precise kinetics of immune reactivity between mice and humans is still not clear. A few other timing and other potentially restricting factors were also mentioned.
Wang Wang, PhD Corresponding Author
Ai-Shun Jin, PhD Professor, Corresponding Author