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As an immunologist with three decades experience, I have received many questions about COVID-19 and the vaccines from family and friends that are not scientists. After further research and review of the currently available data, I have compiled answers to some of the most commonly asked questions explaining the science. This article is only for informational purposes and further resources are available. What is messenger RNA (mRNA) technology? The mRNA technology has become the new buzz term pioneered by Pfizer/BioNTech and Moderna as it forms the bedrock of their new vaccines. Within each of our cells lies a nucleus that contains DNA, our fundamental building block. DNA synthesizes mRNA, the intermediate step between translating protein-encoding DNA and producing proteins essential for our survival. Essentially, mRNA is a mirror image of DNA. The vaccine does not infiltrate or become part of our DNA. How does the COVID-19 mRNA vaccine work? Think of the mRNA vaccine as a delivery system to a subset of cells containing instructions to carry out a specific task. To enter a cell, the COVID-19 virus uses a “spike protein” to bind to a specific receptor on the cell surface, similar to a key opening a lock. After the virus enters the cell, it wreaks havoc, ultimately killing the cell, replicating itself, and then spreads to other cells. These vaccines contain the mRNA code that instructs the cells to produce spike proteins on the cell surface. These spike proteins are then recognized by the immune system, triggering an immune response. This response generates highly specific antibodies against the proteins, mimicking the lock and key analogy and neutralizing the impact of the virus. In addition, the immune system is taught to recognize the spike protein specific to the virus. If this spike protein is encountered in the future, an immune response is swiftly mounted, thus preventing escalation of the virus. Keep in mind:
Is this type of vaccine safe? Although this is the first time that mRNA has been approved in a clinical setting, mRNA technology has been around for three decades in the Research and Development sphere. mRNA vaccines have elicited potent immunity against infectious disease targets in preclinical models and have been used in early clinical trials for influenza virus, Zika virus, rabies virus, and others. 44,000 people were involved in the Pfizer/BioNTech clinical trial and 30,000 people in the Moderna clinical trial. These clinical trials resulted in a greater than 94% efficacy for both vaccines. Some people have experienced severe allergic reactions, however, in most cases, minimal side-effects have been reported for either vaccine. In addition, it is too early to predict the long-term effects, with accuracy, of the vaccines; however, major safety concerns have yet to be identified. Will the vaccine prevent new strains of the virus? Preliminary data suggests that the current mutated strains are more contagious than the original strain. It is possible that the current vaccines could work, at least partially, on these mutated strains if the spike protein is similar enough. Although more research is needed, preliminary Pfizer data shows effectiveness against one of the mutations. Moreover, given that we have accumulated a lot of knowledge and developed these vaccines in a relatively short time-frame, it is feasible that future vaccines will be developed and distributed even quicker. How long does it take for the vaccine to work? It takes time for the immune system to respond to a new antigen and develop a memory whereby it can recognize and respond to a new infection. Both the Pfizer and Moderna vaccines require two doses, 21 and 28 days apart respectively. It is recommended that you wait 2-4 weeks after the second dose of either vaccine to bring protection up to a reliable level. Not everyone responds to the vaccine in a similar manner as it depends on several factors, such as age, medical conditions, and overall health. In fact, a small cohort of people, roughly 5%, may not respond to the vaccine at all. It is recommended that people continue to adhere to wearing masks, social distancing, and practicing good hygiene to curtail transmission as outlined in the CDC guidelines. How does the Astra Zeneca/Oxford vaccine differ from the mRNA vaccines? The Astra Zeneca vaccine, recently approved for distribution in the UK, utilizes a more conventional approach, referred to as a viral vector. This vaccine utilizes a harmless modified version of a common cold virus to deliver the gene encoding for the spike protein into the cell. The vaccine then operates in a similar manner to that of the mRNA vaccine. Resources
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