LEFTY OR RIGHTY? The Science Behind Same-Arm COVID Vaccinations

If you’ve been sniffling and sneezing and testing positive for COVID, I’ve got some not so great news for you. It’s been a year since the last vaccine booster, and according to a 2023 study , you only have about 25% immunity from the COVID viruses circulating right now. And about 15% if you only got the first COVID vaccine.

The good news is that the latest COVID vaccine is about to be approved to help boost your immunity against the virus. And there is actually something you can do to make it even more effective IF ~ you remember which arm you got your last COVID shot it.


A study, published in The Lancet, takes a look at the benefits of same-arm vaccinations. I found it so interesting that I had to turn to one of my favorite infectious disease specialists, Dr. Andrew Jameson with Trinity Health in Grand Rapids to chat more about it.

“It was a really great study” , says Jameson. Since we both have an interest in studies that may be a bit out of the norm it was an enlightening conversation. The study suggests the body may develop a larger immune response due to a localized inflammatory response, leading to improved antibody production and immune memory. Dr. Jameson says it may have to do with your lymph nodes, “If you get your vaccine in the same arm you might be priming the immune cells in your lymph nodes where the antibody production is taking place.”

And there might be something to that. Researchers found after two weeks Killer T cells (the ones that protect you from the most dangerous viruses) were present in 67% of people who got their vaccine in the same arm. That number dropped to 43% when given in different arms.

It’s an interesting study that sheds some light on how the body responds to vaccinations, Dr. Jameson added, “While this research is intriguing, it’s important to note that further studies and clinical trials are needed to confirm these findings. However, it does provide an interesting avenue for potential vaccine optimization in the future.”


Health officials have a lot of confidence that the newest COVID vaccine will give protection against the current circulating COVID virus and it’s variants, with one exception. The latest COVID variant BA.2.86.

Dr. Jameson says if it takes hold as the most dominant variant it could be a game changer, “It’s a big change in variant, similar to the shift from Delta to Omicron. It would be that big of a shift.”

You may remember Omicron caused some of the pandemic’s sharpest spikes in Covid-19 infections when it overtook the Delta variant.

And while the BA.2.86 variant is not included in the latest COVID vaccine, health officials still say it may provide some protection and will still boost your immunity to the other variants which are more widely circulating right now.

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