Is it better to receive the COVID-19 booster dose in the same arm as the primary vaccine, or in the opposite arm?
The answer to this question can be found in this original and interesting article, published in the prestigious journal eBioMedicie, PMID 37574375.
The study was quite simple, so I will keep this post short and sweet.
This study looked at 303 adults who received two doses of COVID-19 vaccines, 6 weeks apart. None of the participants were ill with COVID-19 in between the two doses. There were 147 who received both doses in the same arm (experimental group), and 156 who received the primary dose in one arm and the booster dose in the opposite arm (control group).
Antibody response testing was carried out on all participants two weeks following the second vaccine.
Was there a difference between the antibody results for COVID-19 in the two groups?
Yes, there was!
Several different types of antibodies were tested. Some of the antibodies revealed a statistically significant difference while others did not. For some of the antibodies, a significantly better antibody response was seen in those who received both vaccines in the same arm.
How did the authors explain their findings?
The authors suggest that the explanation to these findings lies in the idea that a part of the immune system’s response is formed in the local lymph nodes that are near the area where the vaccine was injected. And if the lymph nodes in one arm have already been sensitized (as a result of the primary vaccine that was injected in that arm), then a booster injection received in that same arm will be stronger.
Okay, so how does this apply to us? Should we request to be vaccinated in the same arm next time we get a COVID-19 booster? And could this possibly be applicable to all other vaccines, as well? I mean, afterall, some of plan on taking the flu shot vaccine in a couple of weeks. And what about young children who receive vaccine injections in their thighs, does this apply to them as well?
These are all very good questions, but sadly we do not have the answers to them yet.
I tend to inject single vaccines in the non-dominant arm, so that if any pain develops the following day, the dominant, more active arm is spared. But this new study, which will probably prompt the conduction of more studies in the field, suggests meticulously documenting the arm (or leg) in which a primary vaccine was injected so as to consider injecting the booster vaccine in the same one.
In summary, this study is original and quite fascinating. Maybe in a few years, once more studies have been performed and more data is available, we will have to make changes to some of our common vaccine practices. And maybe not. We will just have to wait and see my friends.
And if you want to read more of COVID-19 in infants and children, use this link.
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