| VACCINE ACCEPTANCE |
What You Need to Know About the COVID-19 Vaccines mRNA Technology Has Been Known for Over a Decade, Researched for Flu, Zika, Rabies and More
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he Emergency Use Authorization (EUA) of two vaccines—one by Pfizer, the other by Moderna— that protect against SARS-CoV-2 has been greeted with much appreciation but also with some concern. Some insight into the technology behind these two vaccines, including what is known and what we still need to learn, can help you answer questions from your patients about the safety and efficacy of the vaccines. The National Institutes of Health describe Messenger Ribonucleic Acid, otherwise known as mRNA, as “a single-stranded RNA molecule that is complementary to one of the DNA strands of a gene. The mRNA is an RNA version of the gene that leaves the cell nucleus and moves to the cytoplasm where proteins are made. During protein synthesis, an organelle called a ribosome moves along the mRNA, reads its base sequence, and uses the genetic code to translate each three-base triplet, or codon, into its corresponding amino acid.” Both the Pfizer and the Moderna vaccines use mRNA technology. This technology has been known for over 10 years. It has been studied in preliminary vaccine trials for flu, Zika, rabies and cytomegalovirus. The challenge in these trials was instability of the free RNA, inadequate immune response and inflammatory responses. Numerous clinical studies have been done using mRNA to encode cancer antigens to stimulate immune responses that would clear or reduce malignant tumors. Recent advances in the technology of RNA biology and chemistry have led to the discovery of new delivery systems that improve stability, safety and effectiveness. The current vaccines have strands of mRNA inside a special coating that protects the mRNA from enzymes that might break it down. This coating helps the mRNA enter dendritic cells and macrophages in the lymph node near the vaccination site. The cells then create
part of the spike protein specific to SARS-CoV-2, in a way that is antigenic but will not cause any harm. Our immune system cells then make copies of the spike protein and enzymes in the cells destroy the genetic material from the vaccine. mRNA never enters the nucleus of any cell and cannot change our own genetic material. The protein is recognized as a foreign protein; antibodies, T-lymphocytes and B-lymphocytes destroy it and remain in our bodies to fight the virus if we encounter it in the future. The CDC says mRNA vaccines have several benefits compared to other types of vaccines, including use of a non-infectious element, shorter manufacturing times, and the potential for targeting multiple diseases. mRNA vaccines can be developed in a laboratory using a DNA template and readily available materials. This means the process can be standardized and scaled up, making vaccine development faster than traditional methods. DNA and RNA vaccines typically can be moved more rapidly into clinical trials for initial testing, the CDC adds, noting that future mRNA vaccine technology may allow one vaccine to target multiple diseases. Phase 3 trials of both vaccines showed them to be 95% effective in preventing COVID-19 clinical disease after the second dose. Clinical trials for both vaccines are ongoing. Questions still remain regarding how long immunity lasts and if an immunized person could still harbor the virus and transmit it to others while not getting sick themselves. The first two vaccines approved require two doses, three weeks apart for the Pfizer product and four weeks apart for the Moderna product. Because there have been reports of severe allergic reactions, it is recommended that patients who get the vaccine be observed for a minimum of 15 minutes after inoculation and for up
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Sierra Sacramento Valley Medicine
By Glennah Trochet, MD trochetg@gmail.com