Receiving a COVID-19 booster vaccine in the same arm as the first vaccine dose leads to a faster, more effective immune response than having it in the opposite arm, according to a study in mice and people. The results are described in Cell today1. 'The outcome is important if we did find ourselves in a pandemic setting again, with some other virus that we may then have a new vaccine for,' says co-author Mee Ling Munier, a vaccine researcher at the Kirby Institute at the University of New South Wales in Sydney, Australia. The question of which arm produces a more effective immune response from vaccination has persisted for a long time, says Munier. 'Most people get their vaccine in their non-dominant arm because that doesn't affect their day-to-day life.' But experiments in mice suggest that where a vaccine is given can affect the body's immune response, she adds. When a booster vaccine was administered in the same location as the initial dose, the mice's subcapsular sinus...
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