Vaccine Safety

As more vaccine becomes available, we have heard more questions about vaccine safety. People are concerned about side effects, allergic reactions, and the long-term effects of the Pfizer-BioNTech and Moderna vaccines. This article aims to address these fears.

The CDC released data at the end of January based on COVID-19 vaccinations provided from December 14, 2020 – January 20, 2021. During that time 21,843,033 individuals received 1 or 2 vaccinations. The data showed that a small percentage of people experienced the following side effects, in the order of their commonness: pain, fatigue, headache, myalgia, chills, and fever. These side effects are managed easily with rest and an over-the-counter pain reliever. The few people who are affected to this degree will recover completely within a day or two. I encourage patients to reframe their perception of side effects. Side effects mean that your body has had a strong immune response and your body is learning to protect you from COVID-19.

Allergic reactions to these vaccines are exceptionally rare. Five out of every million people experienced an allergic reaction to the Pfizer-BioNTech vaccine. Just under three people per million experienced an allergic reaction to the Moderna vaccine. Vaccination clinics are set up to monitor recipients for 15 minutes, because reactions to the vaccine usually arise within 10 minutes. Should a reaction occur, clinics are prepared and are able to treat them easily. Most people who experience an allergic reaction are taken to the Emergency Department and are released the same day.

People are also concerned about the potential long-term impact of the COVID-19 vaccine. Both vaccines—Pfizer-BioNTech and Moderna—were developed with mRNA technology, which is a newer way to deliver the protein that helps stimulate the immune response. Because the vaccines are new, complete data is not yet available. Well-trusted peer-reviewed science prohibits reporting claims that cannot be proven. So, while scientists cannot report that there are no long-term side effects, we have good reason to believe that there won’t be. Here are some of the factors leading to our current thoughts on it:

• While mRNA vaccines are new, they have been studied for their use to fight other diseases in humans, including HIV, rabies, Zika, and the flu. No long-term side effects have been discovered.
• mRNA is common in our bodies. Our body makes mRNA and uses it in protein production in all the cells of our bodies.
• mRNA breaks down in the body, dissolves into harmless cellular debris, and is discarded as a part of the body’s normal operations.
• Longer term side effects have occurred in some vaccines in the past. All are extraordinarily rare and have shown up within the first 8 weeks of vaccination.
• Emergency use authorization requires that each company followed vaccine participants for at least 8 weeks. Millions of COVID-19 vaccine recipients are participating in an app-based monitoring system called V-Safe to continue monitoring after patients leave the vaccine clinic. In other words, our monitoring has never been so robust. 
• In all but one of the instances where a side effect arose from vaccine, the disease itself has an exponentially higher risk of bringing on the side effect than the vaccine does. 

Science insists on honesty, both in regard to experiences with other vaccines and not having complete data about these vaccines yet. That makes these vaccines an easy target for those who want to inspire doubt about the vaccines’ safety. What you should know is that it is very highly unlikely that the COVID-19 vaccines will relate to any long-term side effects or an allergic reaction. While there is a small chance of having a manageable side effect or two, this short-lived discomfort is far better than you or your family dealing with COVID-19.  

Marie George, MD, FIDSA, is an infectious disease specialist at Southwestern Vermont Medical Center.