Right or left arm? For the reminder, researchers from Sydney show that it is better to choose the same arm as the primovaccination. The rate of protective antibodies is obtained more quickly, due to a stronger stimulation of the B cells B cells by resident macrophages of the drained lymph node. The results obtained in animals and humans are published in Cell.
For this work, the team first described in animals the biological mechanism at work in the lymph node during reminders and then measured the antibody response in people receiving a recall against the COVID according to the administration arm.
“Macrophages are known to swallow pathogens and eliminate dead cells, but our research suggests that those in lymph nodes near the injection site play a central role by orchestrating an effective vaccination response during the next round. Therefore the location counts ”, Explains Rama Dhenni, researcher at the Garvan Institute and Co-Prime Author of the study.
-A strategy in the event of a pandemic
In mice, researchers have shown that B cells migrate in the outer layer of the local lymph node, where they interact closely with resident macrophages. During a recall in the same arm, the macrophages already sensitized effectively capture the antigen and activate the cells B memory nearby, which then cause the production of antibodies.
Their colleagues from the Kirby Institute then analyzed the response of 30 volunteers after a COVIvin reminder with the PFIZER mRNM vaccine: 20 received in the same arm as the first dose, the other 10 in their opposite arm. “Those who have had the two doses in the same arm produced neutralizing antibodies against the SARS-COV-2 significantly faster, from the first week”, reports Alexandra Carey-Hoppé, from the Kirby Institute, the other co-prime author.
From the fourth week, the two groups presented equivalent antibody levels. “If you have had your injection of covid vaccine in different arms, do not worry, our study shows that over time, the difference in protection decreases. But during a pandemic, the first weeks of protection can make a huge difference on the scale of a population ”, continues Kirby’s researcher. Researchers hope to better understand the interactions between B cells and resident macrophages, with the aim of developing vaccines requiring fewer reminders.
