Sydney scientists have revealed why receiving a booster vaccine in the same arm as your first dose can generate a more effective immune response more quickly. The study, led by the Garvan Institute of Medical Research and the Kirby Institute at UNSW Sydney and published in the journal Cell, offers new insight that could help improve future vaccination strategies.

Immunization introduces a harmless version of a pathogen, known as a vaccine antigen, into the body, which is filtered through lymph nodes—immune ‘training camps’ that train the body to fight off the real pathogen. The researchers previously discovered that memory B cells, which are crucial for generating antibody responses when infections return, linger in the lymph node closest to the injection site.