Research Spotlight: Learning More About the Distribution and Persistence of mRNA Vaccines in the Body

Aram J. Krauson, PhD, of the Department of Pathology at Mass General, is the first author and James Stone, MD, PhD, is the senior author of a new study in NPJ Vaccines, Duration of SARS-CoV-2 mRNA Vaccine Persistence and Factors Associated with Cardiac Involvement in Recently Vaccinated Patients.

Summary

mRNA vaccines are like tiny instruction manuals for your immune system. By injecting the available SARS-CoV-2 vaccine mRNA into your muscle, the vaccine teaches your immune system to recognize and fight the spike protein, without exposing you to the actual virus.

But how long do these vaccines stay in your body and where do they go? The tissue where we detected the vaccines most was in the axillary lymph nodes, located near the armpit where injections are given.

Interestingly, we also detected vaccine mRNA in the heart muscle of three people, all of whom had healing injury that occurred before or around the time of vaccination.

Upon further investigation, our work suggest that the vaccine might have been carried by monocytes/macrophages to the heart as part of their normal function.

What was the question you set out to answer with this study?

How long do mRNA vaccines persist post-injection? What factors contribute to mRNA vaccine detected in the heart?

What Approach Did You Use?

We developed RT-qPCR assays to detect specific mRNA SARS-CoV-2 vaccines in autopsy samples. We screened lymph nodes, heart ventricles, liver and spleen.

Positive samples were further validated by Sanger sequencing of sections outside of the assay target sequence. Tissue samples were further inspected by immunohistochemical (IHC) staining for healing injury and macrophages.

What Did You Find?

30 days of vaccination. There was no detection in any lymph nodes in the chest, liver or spleen.

Cardiac ventricles in which vaccine was detected had healing myocardial injury at the time of vaccination. These ventricles had more myocardial macrophages than the cardiac ventricles in which vaccine was not detected.

Although the effects of these observations are unclear at the present time, it may be prudent to consider delaying LNP-based vaccination in patients with recent myocardial infarction (heart attack).

What are the Implications?

Our study provides a map of where and how long the SARS-CoV-2 mRNA vaccines stay in the body after vaccination.

Given that the SARS-CoV-2 mRNA vaccine was detected in heart muscle with healing injury and that the effects are unclear at the present time, it might be better to delay getting an LNP-based vaccine after a recent heart attack.

As many other LNP-based mRNA vaccines are developed and widely used for multiple types of treatment, understanding how they behave in the body will help us improve their safety and effectiveness.

About the Massachusetts General Hospital

Massachusetts General Hospital, founded in 1811, is the original and largest teaching hospital of Harvard Medical School. The Mass General Research Institute conducts the largest hospital-based research program in the nation, with annual research operations of more than $1 billion and comprises more than 9,500 researchers working across more than 30 institutes, centers and departments. In July 2022, Mass General was named #8 in the U.S. News & World Report list of "America’s Best Hospitals." MGH is a founding member of the Mass General Brigham healthcare system.