What Makes COVID-19 Vaccines Safe And Effective

Caesar Djavaherian, MD, MS, FACEP
January 29, 2021
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Vaccines have been critical to maintaining public health for generations, ever since the first smallpox vaccine was created in 1798. The concept of vaccination is quite simple. Inject a small amount of a disease or virus into your body to encourage an immune response where the body builds antibodies to fight the invading virus or disease if it tries to infect you in the future. This tremendous discovery has helped us control measles, mumps, rubella, tetanus, and many other diseases.

Today, COVID-19 vaccines nurture the same response from the body – to train those immune cells when needed – but with a slightly different mode of delivery. These vaccines have been developed and tested with unprecedented speed as well, so many people, understandably, have questions about how they work and their safety. Here’s a look at the different types of COVID-19 vaccines available today, the unique way they work, and why you can be confident in their safety and efficacy.

What Makes the COVID-19 Vaccines Unique and Effective

Currently, the U.S. Food & Drug Administration (FDA) has issued emergency-use authorization for two COVID-19 vaccines. They are commonly referred to as the “Pfizer” and “Moderna” vaccines, named after the companies involved with developing and distributing them. They are mRNA (messenger RNA) vaccines, which refers to the unique way they create the needed immune response in your body.

These vaccines do not have a live virus in them. Instead, they use a small piece of genetic code, much like a blueprint, for the COVID-19 spike protein, a small harmless protein found on the surface of the virus, placed inside a fat molecule. When injected, your body begins to produce its own COVID-19 spike proteins and subsequently initiates antibody production to fight them. The major benefit of mRNA vaccines is that the body learns to fight the virus without injecting a portion of the actual virus, which eliminates the risk of you actually getting COVID-19 by getting the vaccine. Both vaccines require two doses for maximum effectiveness. The Pfizer vaccines should be given 21 days apart and the Moderna vaccines 28 days apart.

While the delivery method sounds novel, mRNA vaccines have been under study for decades and were fast-tracked as potential solutions when the severity of the COVID-19 pandemic became more clear in the first half of 2020. In the past, these vaccines have been studied for illnesses such as Zika, rabies, flu, and cytomegalovirus (CMV). The hope is that one mRNA vaccine may be able to offer spike protein instructions for multiple illnesses in one injection in the future. Both COVID-19 mRNA vaccines demonstrated a nearly 95% efficacy rate in preventing COVID-19 at least 14 days after the second dose.

One More Thing About Your Immune Response

Early on, as vaccines were being tested, and as the medical community learned more about COVID-19 from people who were in recovery, there were concerns about how long the body still produced antibodies after overcoming the infection. Basic long-standing scientific research addresses this.

As time passes, the body’s T-lymphocytes and B-lymphocytes (white blood cells) remember the virus and regenerate the antibodies in the future should the virus show up again. While we are still collecting a tremendous amount of information about the COVID-19 vaccine as well as the coronavirus in general, there is no reason to believe this natural immune response isn’t occurring today in those who are being vaccinated and those who have already overcome the virus.

There are data, however, to support that those who have been infected and recovered from COVID-19 have less of an immune response than those who have never been infected and should, therefore, still be vaccinated.

Addressing Vaccine Safety Concerns

Because of the fast-tracked nature of developing these drugs, you may be asking about safety. The vaccines were thoroughly studied in three-phase randomized trials, with more than 43,000 participants involved in the Pfizer study and more than 30,000 in the Moderna study.

It’s also important to remember that safety hasn’t taken a backseat since the trials were completed. The CDC has implemented expanded safety monitoring systems to continuously track the efficacy and safety of the vaccines are they are being given. Some of the systems and checks in place include the CDC’s V-Safe smartphone health checker app, which allows those who have taken the vaccine to tell the CDC about side effects. The National Healthcare Safety Network (NHSN) also exists to monitor acute and long-term care facilities, and the FDA continues to collect insurance and payer database data for surveillance and research.

A few relatively minor side effects reported from those who have taken the vaccine include:

  • Pain or swelling at the injection site
  • Fever, chills
  • Fatigue
  • Headache

If pain at the vaccine injection site does not go away after 24 hours or if other symptoms don’t resolve themselves within a few days, call your physician.

More COVID-19 Vaccines in the Works

Currently, COVID-19 vaccines from AstraZeneca and Johnson & Johnson are still being studied and reviewed. These vaccines are called adenovirus immunizations and involve inserting the spike protein into an actual adenovirus molecule. Adenoviruses were discovered in the 1950s and usually cause mild respiratory or gastrointestinal infections, but some researchers still claim they are a beneficial or “tried and true” way to initiate an immune response.

Novavax, another manufacturer, is testing a vaccine with the spike protein administered inside an adjuvant, or a molecule it believes will further enhance the immune response.

Some of these vaccines have been approved in other countries, but are not approved in the United States at this time. As research trials continue, and, hopefully, yield the needed positive efficacy and safety results, there may be other vaccine options available in the U.S. as well.

Caesar Djavaherian, MD, MS, FACEP

Caesar Djavaherian, MD FACEP, is the Chief Clinical Innovation Officer at Carbon Health. 


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