osomocosoRN t1_j4yzpom wrote
Vaccines are administered into a muscle because its a highly vascularized tissue. This means there’s a lot of blood vessels that supply muscle. Therefore, the vaccine can become detected by the immune cells in your blood and your body can initiate the immune process. You want to avoid administration into fat tissue because it is not as vascularized, leading to delayed absorption and possible denaturing (or breakdown) of the vaccine. The deltoid muscle of your arm is a great spot because it often has only a thin layer of fat and a thicker layer of muscle. This site has also been shown as a safe route because of the relatively lower risk in puncturing a major nerve. If you were to inject into something like a foot, you run the risk of missing a muscle and/or puncturing a nerve.
Silverjeyjey44 t1_j506msc wrote
Any research why not intravenously?
Moldy_Teapot t1_j50ndyl wrote
I can't speak to how it would affect the vaccine and the body's response to it, but I can say that giving a vaccine Intravenously is impractical and potentially dangerous at scale. I work in an ER and it can easily take 20+ minutes to start an IV on a patient, especially if they're very young or very old. That's compared to administering Intramuscularly which will take 2 or 3 minutes at most. From what research we've done on vaccines, doing it intramuscularly is perfectly fine so there's just no reason to change that. There's also a greater risk of sepsis going from IM to IV since you're opening a path directly into your bloodstream instead of just near it (again I can't speak to whether or not the vaccine itself would cause issues, but I can't imagine it would help).
volyund t1_j5118c4 wrote
Because you don't want something immunogenic circulating in your bloodstream. That's how you get cytokine release syndrome, shock, and dead patients. You want localized immune reaction somewhere safe (like an arm), where immune cells can be recruited to from blood , tissue, or lymph; to do their thing.
im_thatoneguy t1_j5164ex wrote
One reason recently is illustrated by the rare cardiac side effects from the various Covid vaccines. There's evidence to suggest that the virus' spike proteins themselves can cause damage to cells even just as non-functional fragments. So a sore and inflamed arm muscle from your deltoid muscle cells reacting to the spike proteins is fine. But if your heart gets hit by a bunch of Covid Spike proteins and gets inflamed that may be what's causing myocarditis even though they aren't being infected by a virus.
YouAreGenuinelyDumb t1_j51ituv wrote
Do the spike proteins from the mRNA typically remain local in deltoid muscle or do they distribute in significant quantity around the body?
im_thatoneguy t1_j51pb6h wrote
I believe that's still a point of interest without a definitive answer. There are studies which showthere is circulating spike protein. There are studies which show similar levels of S Protein circulation between vaccination and infection. But there are also studies showing that infection causes higher rates of myocarditis. Both could be true (Spike Protein could be one cause of myocarditis and the higher rates of myocarditis in infected patients being due to compounding causes in addition to the circulating S protein.) But I don't think there is even a definitive answer yet on whether the spike proteins are exclusively responsible for all of the vaccine induced myocarditis.
YouAreGenuinelyDumb t1_j51wjrb wrote
Thank you for the links and answer!
I wonder if the LNP’s may be behind some of the cases. There was a possible vaccine-induced myocarditis in the Novavax trial, which are LNPs with recombinant protein S. Although the the fact that it contains protein S may be confounding.
[deleted] t1_j50m5ad wrote
[removed]
Supraspinator t1_j51gc4f wrote
At least for the mRNA vaccines, intravenous injection could be dangerous. In a mouse model, intravenous injection of the vaccine caused myocarditis, so accidental intravenous injection has been suggested as cause for vaccine-induced myocarditis.
[deleted] t1_j4zhg2a wrote
[removed]
Viewing a single comment thread. View all comments