Researchers at Garvan Institute of Medical Research and Kirby Institute at UNSW Sydney have discovered why injecting a vaccine booster in the same arm as the first dose can generate a more effective immune response. The study found that macrophage cells, located in lymph nodes, play a crucial role in directing the positioning of memory B cells to respond better to vaccines.
When a vaccine is administered, macrophages become “primed” inside lymph nodes and guide the positioning of memory B cells. These primed macrophages then capture antigens and activate memory B cells to produce high-quality antibodies when a booster shot is given in the same arm. This approach significantly enhances the immune response.
The researchers validated their findings in human participants receiving a COVID vaccine, demonstrating that boosting vaccine responses in the same arm as the first dose generates superior depth and breadth of recall responses. The study’s results suggest that administering vaccines in the same arm can provide early protection against variants like Delta and Omicron.
The discovery has significant implications for refining vaccination approaches and designing next-generation vaccines with enhanced effectiveness. By understanding how to replicate or enhance interactions between memory B cells and macrophages, researchers may be able to create more effective vaccines requiring fewer boosters.
Source: https://www.genengnews.com/topics/infectious-diseases/location-does-matter-study-finds-site-of-second-vaccine-dose-impacts-on-immune-response