COVID Vaccines: Understanding the New Technology Used to Fight the Virus

Published on February 17, 2021

The consequences of coronavirus disease 2019 (COVID-19, or COVID) have been devastating since its emergence in December 2019, with more than 100 million cases and 2 million deaths globally.1 Our day-to-day work and social activities have been significantly hampered. Schools have shut down (hello, remote learning), international travel to many countries has been banned (goodbye, vacations), and many businesses have been forced to shutter. What was supposed to last a couple of weeks—as we’d initially hoped—has lasted over a year. And although precautions such as frequent handwashing, social distancing, mask wearing, and quarantining after viral exposure or during illness can limit COVID spread, there have been challenges with rigorous implementation.2 

The good news is that, as of December 2020—exactly 1 year after the first reported case of COVID—two vaccines have been granted emergency use authorization from the FDA and become available in the US.3,4 Pfizer-BioNTech BNT162b2 and Moderna mRNA-1273 are exciting because they not only reduce viral spread and offer a chance to end the pandemic but also use a new vaccine technology called messenger ribonucleic acid (mRNA). But what exactly is an mRNA vaccine? Will it alter our DNA and therefore give us the disease? Is it safe? These great questions are often asked by individuals deciding whether to get vaccinated.  

First, let’s understand how the mRNA vaccine works. Unlike the conventional flu vaccine that triggers an immune response after injection of a weakened or inactivated version of the virus,5 the mRNA vaccine doesn’t use a live virus, which means that it can’t give us COVID.6 Instead, once injected, the mRNA signals our cells to make a specific protein (spike protein) found on the virus (severe acute respiratory syndrome coronavirus -2 [SARS-CoV-2]) that causes COVID. Our immune system then recognizes the spike protein as an invader and builds antibodies to destroy it. Once antibodies are made, our bodies will continue to recognize the virus, which reduces our chance of illness if exposed. Also, mRNA never reaches the cell nucleus, where our DNA is, which means that these vaccines don’t affect our DNA.6  

These vaccines’ efficacy is also impressive, with the Pfizer vaccine being 95% efficacious 7 days after the second dose7 and the Moderna vaccine being 94.1% efficacious 14 days after the second dose.8 These results come from two phase 3 clinical trials that collectively enrolled more than 73,000 volunteers who received either vaccine or placebo. The findings also showed the vaccines to be safe: The most common side effects were also similar between the two and included injection-site pain, swelling, or redness and generalized chills, tiredness, or headache. These side effects were usually mild to moderate and typically occurred within 7 days after vaccination.7-10 To ensure that the vaccination benefits continue to outweigh the risks, safety systems are monitoring for adverse events or long-term side effects not observed during the clinical trials.11 Experts will determine whether to change vaccine recommendations if such effects occur. 

Debating which vaccine to get? Both are mRNA based, with similar efficacy and safety results, and require two injections for maximum protection, with an interval of 21 days for BNT162b2 and 28 days for mRNA-1273.9,10 The Advisory Committee on Immunization Practices doesn’t recommend one vaccine over the other, but the second dose should be the same product as the first.12 

If you decide to get the COVID vaccine, remember: By getting the vaccine, you’re not only less likely to contract or spread the virus but are also playing a large role in helping stop the pandemic.  

To best protect yourself and others from contracting the virus, follow Centers for Disease Control and Prevention’s recommendations of getting vaccinated, continuing social distancing, and wearing a mask.13  

For more information on clinical trials investigating other potential COVID vaccines, visit  


  1. Johns Hopkins University & Medicine. COVID-19 dashboard by the Center for Systems Science and Engineering (CSSE) at Johns Hopkins University. Coronavirus Resource Center. Accessed January 29, 2021. 
  2. Centers for Disease Control and Prevention. COVID-19: How to protect yourself & others. Centers for Disease Control and Prevention. Accessed January 29, 2021. 
  3. United States Food & Drug Administration. Pfizer-BioNTech COVID-19 vaccine. United States Food & Drug Administration. Accessed January 29, 2021.  
  4. United States Food & Drug Administration. Moderna COVID-19 Vaccine. United States Food and Drug Administration. Accessed January 29, 2021.  
  5. World Health Organization. How do vaccines work? World Health Organization. Accessed January 29, 2021. 
  6. Centers for Disease Control and Prevention. Understanding mRNA COVID-19 vaccines. Centers for Disease Control and Prevention. Accessed January 29, 2021. 
  7. Polack FP, Thomas SJ, Kitchin N, et al. Safety and efficacy of the BNT162b2 mRNA Covid-19 vaccine. N Engl J Med. 2020;383(27):2603-2615.  
  8. Baden LR, El Sahly HM, Essink B. Efficacy and safety of the mRNA-1273 SARS-CoV-2 vaccine. N Engl J Med.  Published online December 30, 2020. doi:10.1056/NEJMoa2035389  
  9. Centers for Disease Control and Prevention. Information about the Pfizer-BioNTech COVID-19 vaccine. Centers for Disease Control and Prevention. Accessed January 29, 2021. 
  10. Centers for Disease Control and Prevention. Information about the Moderna COVID-19 vaccine. Centers for Disease Control and Prevention. Accessed January 29, 2021. 
  11. Centers for Disease Control and Prevention. Ensuring the safety of COVID-19 vaccines in the United States. Centers for Disease Control and Prevention. Accessed January 29, 2021. 
  12. Centers for Disease Control and Prevention. Interim clinical considerations for use of mRNA  
    COVID-19 vaccines currently authorized in the United States. Accessed January 29, 2021. 
  13. Centers for Disease Control and Prevention. Benefits of getting a COVID-19 vaccine. Centers for Disease Control and Prevention. Accessed January 29, 2021.  


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