Vaccine components and myocarditis

Where do spike proteins go?

The mRNA molecule

Whether natural or delivered through an injection, the mRNA molecule operates like a temporary blueprint in the the cytoplasm of a cell to make proteins that the body uses for various functions.

mRNA vaccines: how long do its components last in the body?

Just like naturally occurring mRNA, mRNA from COVID-19 vaccines lasts about 2–3 days in the body before becoming completely absorbed. During the 2–3 days, vaccine-delivered mRNA begins building SARS-COV-2 spike proteins, using the body’s own cellular materials and mechanisms. Spike proteins stay in the body longer than mRNA molecules, but not indefinitely, estimated to be about the same amount of time as other proteins that the body makes and then absorbs — or “a few weeks.”

Where do mRNA from the vaccine and its spike proteins go?

mRNA from the vaccine is thought to stay in the cytoplasm of muscle cells near the point of injection (usually in the upper arm) and in lymph nodes nearby, before getting completely absorbed. Spike proteins are thought to stay mostly locally, as well, residing for a few weeks in the cytoplasm and intracellular spaces of the arm muscle cells and in nearby lymph nodes.

What, then, related to the vaccine, circulates through the body and lasts a long time?

During the time that the spike protein is present, the body perceives an invader and a natural immune response takes place. The natural immune system generates antibodies and immune cells specific to fighting the spike protein. These immune products circulate through the blood and lymph system throughout the body. Some become “memory cells” residing for a long time (months, years, maybe longer for some people) residing mostly in the lymph system. Memory cells will “remember” the invader (the spike protein) and can activate an immune response if a vaccinated individual later comes in contact with a SARS-COV-2 variant close enough to the one against which they were immunized. See this 3-minute video about how COVID-19 vaccines work. Or, this excellent 2-minute video (you may need a brief course in immunology to follow this video completely).

Myocarditis, a possible theory:

A theory based on mouse studies may help explain the rare side effects of myocarditis and pericarditis after vaccination: If an injection needle hits a strong enough vein during administration of the vaccine (thought to be an extremely rare event), this accidental occurrence could lead to an increase in the risk of adverse outcomes. The hypothesized reason is that some of the mRNA gets transported via the blood to tissue beyond the arm muscle, eventually landing in places like the pericardium.

Veins present at the injection area of the upper arm are considered to be so small as to collapse if stuck by a needle. It may be possible, however, as recent mouse studies suggest, that some veins might be able to carry the vaccine into circulation. This is currently a theory. The theory does not explain why teenagers, especially boys, are more prone to myocarditis.

Some scientist now recommend aspiration of the needle during vaccination to avoid injecting into a vein. Currently, needle aspiration is deemed unnecessary and is not routinely recommended due to causing additional localized pain and increased resistance from the public. Public health leaders are tasked with the responsibility of deciding on the benefits of one approach versus the other — and the drawbacks of each.