Receiving a second dose of COVID-19 vaccine in the same arm as the first elicits a speedy immune response.Credit: Genaro Molina/Los Angeles Times via Getty
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.
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Munier and her colleagues found that specialized immune cells called subcapsular sinus macrophages in mouse lymph nodes, play an important part in mounting an immune response to vaccination.
When a booster vaccine was administered in the same location as the initial dose, the mice’s subcapsular sinus macrophages were already primed. They reactivated immune cells called memory B cells more quickly than did the cells of mice whose second vaccination was administered in a different limb.
