Unsure about the COVID-19 vaccine? UF Health’s chief epidemiologist has answers

As access to the COVID-19 vaccines contines to grow, one major challenge still looms large: vaccine hesitancy. Yet acceptance of the vaccine appears to be growing: A poll by the Kaiser Family Foundation in mid-January found a growing share of the public — 47% — is open to getting inoculated or has already done so. In December, a similar poll registered 13% lower. Here, Nicole M. Iovine, M.D., Ph.D., chief epidemiology officer for the University of Florida Health Shands Hospital system, addresses key issues related to overcoming vaccine hesitancy.

Question: As a physician and epidemiologist, what kinds of concerns have you been hearing about the vaccines?

Answer: I’ve heard people say that the vaccine was developed too quickly, and I reassure them that all the steps that are necessary to bring any vaccine to the public have been followed for the COVID-19 vaccines. All the studies, data analyses, oversight by scientific government agencies, and the follow-up of vaccine study participants — all of that occurred and continues to occur for the COVID-19 vaccines. No steps were skipped.

The other concerns I hear have to do with the biology of the vaccine. People ask if the vaccine will interfere with or become part of their DNA, be passed on to future generations, or affect their fertility. I explain that our DNA is kept in a special compartment within our cells (the nucleus), which prevents anything from the outer part of the cell (the cytoplasm) from entering when it shouldn’t. This make sense since it is so important to preserve the integrity of our DNA, since it is what makes us who we are. The messenger RNA, or mRNA, in the vaccine cannot gain access at all to our DNA and cannot be passed on to a future generation or affect our fertility. The mRNA in the vaccine stays in our cells only long enough for the spike protein to be made, and then the mRNA is degraded along with all the other, normal mRNAs that our bodies need to make other proteins. The vaccine mRNA does not persist in our cells, and we can’t make the spike protein forever. It is made for only a short period of time, but just enough for our immune systems to recognize it and make the protective antibodies we need.

Q: If I have had COVID-19, why should I still get a vaccine?

A: People who have recovered from COVID-19 produce many different antibodies against the virus. That may sound good, but in reality only a small fraction of those antibodies is able to actually prevent infection. These are called neutralizing antibodies, and are typically directed against the spike protein of the virus. The rest of the antibodies can recognize the virus, but can’t prevent it from infecting our cells. The COVID-19 vaccine contains the instructions to only make a part of the virus spike protein. Your immune system will focus its entire response on making just those neutralizing antibodies against the spike protein. In this way, your immune system creates a high level of exactly the antibodies needed to prevent infection. Even if you’ve had COVID-19, getting the vaccine will ensure that you have a high level of protective antibodies.

Q: Why should I still wear a mask after getting the COVID-19 vaccine?

A: It is very important to continue to wear a mask, practice physical distancing, avoid large gatherings and keep your hands clean even after getting the COVID-19 vaccine. The problem is that we don’t yet know if vaccinated persons can still spread the virus to other people. Even though you are protected from getting sick with COVID-19 if you are vaccinated, it is possible it could still be in your nasal passages and be spread to others. As more studies are done, we will hopefully get an answer to this question. 

Q: What procedures are in place to find and evaluate side effects as vaccinations continue?

A: The pharmaceutical companies are still following up on the people who received their vaccines in the studies that were done to show that the vaccines work. Also, since 1990 there has been a Vaccine Adverse Event Reporting System, or VAERS, run by the Centers for Disease Control and Prevention and the Food and Drug Administration to track vaccine safety. If any health problem happens after vaccination, anyone — doctors, nurses, vaccine manufacturers and any member of the general public — can submit a report to VAERS. 

Q: What is your assessment of the latest figures on side effects from the Pfizer and Moderna vaccines?

A: The COVID-19 vaccines have been shown to be very safe, and the number of serious adverse events are similar to that of other, more familiar vaccines, such as the flu vaccine. Some people develop adverse events that are not considered serious but can be uncomfortable. Many people will develop soreness at the injection site, similar to what happens when other vaccines are given. Some people will have other side effects like fever or headache, or may feel ill with general body aches as if they have the flu. These reactions can be treated with over-the-counter medications like acetaminophen (Tylenol) or anti-inflammatory medications including ibuprofen (Advil or Motrin) or naproxen (Aleve), and resolve within a day or two.The thing to remember is these side effects are all signs that your immune system is working as it should. When your immune system is working hard to mount a response against an infection or a vaccine, it can trigger all these symptoms. Even though it can be uncomfortable, be assured that these are normal reactions.

Q: How much is known right now about vaccine efficacy among various demographic groups?

A: Both the Pfizer and Moderna vaccine studies included persons of different ages and from different ethnicities, racial groups and countries, and the efficacy was similar across them. 

Q: As more doses are administered, what are epidemiologists and other experts learning about the vaccine that perhaps they didn’t know before?

A: An important question is the duration of the immune response. That will help determine whether a person is protected for several years or if the COVID-19 vaccine will have to become an annual vaccine like the flu shot.

Q: Is there a commonly accepted vaccination-rate threshold that is needed to reach herd immunity?

A: Herd immunity for COVID-19 means that so many people are immune to it that even people who are not immune are unlikely to become infected because it is too hard for the virus to find that susceptible person. Vaccination is the best way to get to herd immunity quickly and safely. However, the number of people who need to be immune to reach herd immunity is different for each virus. This is mainly because the more infectious a virus is, the more people will have to become immune in order to stop its spread. We don’t know precisely what percent of the population needs to be immune to reach this level, but it is expected to be at least 85%. Despite the COVID-19 surges in Florida, it is estimated that less than 20% of the population has any level of immunity to COVID-19. This why it is so important to get vaccinated!

Media contact: Ken Garcia at kdgarcia@ufl.edu or 352-273-9799.


Learn more about UF Health's efforts to combat the COVID-19 pandemic at Coronavirus.UFHealth.org.

About the Author

Doug Bennett's picture

Doug Bennett

Science Writer, Editor

Doug Bennett joined the UF Health staff in January 2015 as a science writer and editor. His topic areas include anatomy; biochemistry and molecular biology; molecular genetics and microbiology; pathology,...Read More