Using same arm for vaccination boosts antibody response: Study

Do you tend to administer boosters in the same arm as the initial vaccination? Or are you not convinced it matters? 
 
Early research carried out by a group of Sydney-based scientists is adding weight to the suggestion that using the same site for follow-up vaccination could hasten the body’s immune response.
 
The scientists from the Garvan Institute of Medical Research and the Kirby Institute at UNSW Sydney say the findings, published in the journal Cell, could help shape and improve vaccination strategies.  
 
They explored the response of macrophages when a vaccine booster is administered, building on previous work which found memory B cells linger in the lymph node closest to the injection site.
 
Using intravital imaging, researchers found the cells move to the outer reaches of the lymph node and interact closely with resident macrophages, which then capture antigens and prompt memory B cells to produce antibodies more efficiently following a booster.
 
‘Boosting vaccines in the same arm leads to more rapid secretion of broadly neutralising antibodies,’ the authors concluded.
 
The research was initially carried out using mice, with a further trial including 30 healthy humans supporting the findings.
 
Participants, who were recruited in 2021 and had no history of COVID-19 infection, received a second booster dose of the Pfizer vaccine, with 20 receiving it in the same arm as the initial injection, and the others in the opposite arm.
 
The authors found those with both doses in the same arm produced neutralising antibodies ‘significantly faster’.
 
‘Macrophages are known to gobble up pathogens and clear away dead cells, but our research suggests the ones in the lymph nodes closest to the injection site also play a central role in orchestrating an effective vaccine response the next time around,’ said Dr Rama Dhenni, a study co-author.
 
‘So, location does matter.’
 
According to Dr Mee Ling Munier, co-senior author and Vaccine Immunogenomics group leader at the Kirby Institute, the antibodies from the same-arm group were also more effective against COVID-19 variants such as Delta and Omicron.
 
‘By four weeks, both groups had similar antibody levels, but that early protection could be crucial during an outbreak,’ she said.  
 
‘If you’ve had your COVID jabs in different arms, don’t worry – our research shows that over time the difference in protection diminishes.’
 
‘But during a pandemic, those first weeks of protection could make an enormous difference at a population level.
 
‘The same-arm strategy could help achieve herd immunity faster – particularly important for rapidly mutating viruses where speed of response matters.’
 
According to the authors, the work provides further evidence for refining vaccination strategies and enhancing vaccine effectiveness.
 
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