Five Questions About the COVID Vaccines

Dr. Susanna Naggie has some reassuring facts to share

With two vaccines being rolled out under emergency use approval from the Food and Drug Administration, health care workers and others with high risk of Covid exposure are now being vaccinated at Duke and elsewhere around the country.

We asked infectious disease specialist Dr. Susanna Naggie of Duke Health to answer some of the common questions the public has been raising about these vaccines.


DT:  We’ve been hearing that a vaccine takes years to develop, but this one arrived in less than nine months. Did the drug companies or the FDA cut some corners to make this happen faster?

Susanna Naggie, MDNaggie: There was no corner-cutting as it relates to safety and efficacy evaluations. The FDA has different pathways for drugs or vaccines to progress through regulatory review. There are expedited pathways for drugs or vaccines that will offer a therapy or preventative for a disease that does not already exist. In the setting of a national emergency, as was declared to the Secretary of DHHS due to the COVID pandemic, the pathway can be accelerated. This means that the typical “wait times” for drugs or vaccines that usually occur are removed. The COVID vaccines got to skip to the front of the line because they are prioritized. The size of the study population is the same as you would see in any vaccine study.

The follow-up time is shorter here, so the number of events required for an emergency use authorization are fewer than for an approval, and the amount of time of follow-up from the last vaccine dose is less than you would normally have for an FDA approval – which is why this is called an emergency use authorization. It is not an approval, these vaccines remain investigational until the companies come back to the FDA and submit their data for a full FDA approval. This will happen. However, with emergency use authorization, we now get access to the vaccine more quickly and in the setting of a pandemic that is killing thousands of Americans every day, that is really important.


DT:  This vaccine is supposedly 95 percent effective. Would it be better to wait until there’s something better?

Naggie: It is hard to get much better than 95% for a vaccine. There are few vaccines currently available that are more efficacious than this. We really could not have hoped for a more efficacious vaccine(s).


DT:  What sorts of side effects come with the Pfizer vaccine and are there groups of people who should probably not get the shot because of those?

Naggie: The side effects are primarily those that we are used to seeing with vaccines including local and systemic reactions. The most common local reaction is pain followed on a much lower frequency by redness or swelling at the site of the injection. Most common systemic reactions include fatigue, headache, chills, muscle and/or joint pain followed on a much lower frequency by vomiting, diarrhea, and fever. The local and systemic reactions are due to the development of a healthy immune response which is the goal of the vaccination and are more common after the second dose. 

Anaphylaxis (severe allergic reaction) has been reported, so anyone with known allergy to the components of the vaccine should not receive the vaccine: Each dose of the Pfizer-BioNTech COVID-19 Vaccine also includes the following ingredients: lipids (0.43 mg (4-hydroxybutyl)azanediyl)bis(hexane-6,1-diyl)bis(2-hexyldecanoate), 0.05 mg 2[(polyethylene glycol)-2000]-N,N-ditetradecylacetamide, 0.09 mg 1,2-distearoyl-sn-glycero-3-phosphocholine, and 0.2 mg cholesterol), 0.01 mg potassium chloride, 0.01 mg monobasic potassium phosphate, 0.36 mg sodium chloride, 0.07 mg dibasic sodium phosphate dihydrate, and 6 mg sucrose. The dilutent (0.9% Sodium Chloride Injection, USP) contributes an additional 2.16 mg sodium chloride per dose.

The Pfizer-BioNTech COVID-19 Vaccine does not contain preservative. The vial stoppers are not made with natural rubber latex.


DT:  Why did the FDA draw the line on the Pfizer-BioNTech vaccine at 16 years and older? When can younger children be protected?

Naggie: The authorization in age 16 and older is based on data in these populations. The first large randomized controlled trial included adults 18 years and older. For the Pfizer vaccine, children aged 16 and 17 were included later and had some early data which supported the authorization in this age group. Studies enrolling children down to age 12 are now ongoing and there is a plan to enroll younger children. As dosing and safety are supported in younger children, we would hope to see the authorization expanded.


DT: If this vaccine is based on a piece of RNA from the virus itself, how do we know it’s not going to harm us?

Naggie: The mRNA vaccines (Pfizer and Moderna) are not using part of the virus itself. They are using scientifically engineered mRNA, which our bodies are well equipped to recognize and decode, that encodes only for the spike protein on the virus. So this is not a live viral vaccine or an attenuated virus vaccine, it is using laboratory engineered codes that our bodies recognize and translate into protein that looks like the virus to our immune system. It allows our immune system to develop immunity to the virus without ever being exposed to the virus. Since mRNA is natural to our bodies, our body naturally degrades the mRNA, so it does not last very long in our body, but it is there long enough for our body to develop immune recognition and memory, so that if our body ever sees the real virus, it knows how to fight it. 

Infectious disease specialist Susanna Naggie MD is an associate professor of medicine and vice dean for clinical research in the Duke Clinical Research Institute.