COVID-19 Vaccine FAQ Series - Questions about efficacy and safety

Midwest Allergy Sinus Asthma, SC

COVID-19 Vaccine FAQ Series
By Tamara Reeter, NP and Dareen Siri, MD
*created 1/7/21 and subject to change.

Many of our patients are asking us about details regarding COVID-19 and the COVID-19 vaccines. Given MASA, the Food Allergy Center, and SWIA’s expertise in allergy, immunology, medicine and clinical research, we have collected and digested information from validated sources as we begin a Q&A series which will address the majority of questions that our patients have. These documents are intended for general information and should not be taken as specific advice to your particular situation since good care for all patients should be individualized.

Announcement to Patients about COVID-19 (March 2020)
Q&A 1. Background on COVID-19
Q&A 2. What you need to know about the COVID-19 Vaccine.
Q&A 3. Questions about efficacy and safety.
Q&A 4. Questions about allergies, advice, and special circumstances.

In this section, we address questions of efficacy and safety.

1. Is the COVID-19 vaccine FDA approved and is it safe?

The first COVID-19 vaccines are being used under Emergency Use Authorizations (EUA) from the U.S. Food and Drug Administration (FDA). Many other vaccines are still being developed and tested. Tens of thousands of people have participated in clinical trials in the development of the COVID-19, with doctors and scientists evaluating their safety and effectiveness prior to the availability to the public. Specifically with the COVID-19 vaccine development, there has been an unprecedented effort globally among various organizations, industry, and governments to share information and work together to bring forth solutions to the pandemic.​ ​“The safety of COVID-19 vaccines is a top priority. The U.S. vaccine safety system ensures that all vaccines

are as safe as possible.” The v-safe appwas developed to make reporting easy, real-time, and accessible to all people. (see the previous section about the v-safe app)

2. How effective are the COVID-19 vaccines?

In a very large scale clinical trial involving 40,000+ people, the Pfizer-BioNTech COVID-19 vaccine was demonstrated to be 95% effective, when given in two doses approximately 3 weeks apart. Vaccine efficacy exceeded 90% in almost all groups regardless of age (16+ years old), gender, body size, ethnicity, and the presence of coexisting health conditions. The vaccine starts to work as soon as the immune system begins to respond, indicating that even early partial response can afford protection. During the trial, researchers noted that the incidence of COVID-19 was noticeably higher in people who received the placebo vaccine as early as 12 days from injection. Graphically, the rate of COVID-19 in those who received the vaccine remained flat in comparison to the proportional and steady increase in COVID-19 cases in those who did not receive the vaccine (placebo subjects). During this trial, there were no deaths from COVID-19.

In a very large scale clinical trial involving ~30,000 people, the Moderna COVID-19 vaccine demonstrated 94.1% efficacy in preventing COVID-19, including severe disease. The efficacy of the COVID-19 vaccine exceeded 90% in all groups under 65 years, genders, ethnicities, and regardless of high COVID-19 risk status. The efficacy in people 65 years and up was 86.4%. During the trial, 30 people developed severe COVID-19. All 30 were in the placebo group (persons who did not get the COVID-19 vaccine), and one person in this group died from COVID-19. Five additional deaths were noted during the clinical trial in both the placebo and the vaccinated groups from unrelated causes.

It is important to note that the efficacy of the COVID-19 vaccines is high compared to the influenza vaccine (“the flu shot”). However, influenza trials and evaluation of the efficacy of the influenza vaccines have not occurred during times of public precautions and social distancing, which undoubtedly have decreased disease transmission. A caveat to the efficacy data should also be noted, since the clinical studies noted above were from short-term data. Longer term studies are needed to evaluate the persistence of antibodies and a high level of protection months and years down the road.

3. What are the side effects of the COVID-19 vaccine? Can it make me sick?

You cannot get COVID-19 from the COVID-19 vaccine. None of the COVID-19 vaccines contain the live virus that causes COVID-19 so a COVID-19 vaccine cannot make you sick with COVID-19. After COVID-19 vaccination, you may have some side effects. This is a normal sign that your body is building protection. Common side effects include local pain, redness, and swelling at the injection site. You may also experience fever, fatigue, chills, and headache for a day or two after the vaccination. Since your body’s immune system is busy trying to mount an immune response, you should do your best to allow your body to protect you. This may include getting plenty of rest and sleep, eating healthfully, reducing stress, and avoiding overworking

and getting other infections. Below is a summary of side effects reported during the clinical trials for both vaccines.


Pfizer Vaccine

Moderna Vaccine

Local Reactions

Injection site pain (83% in younger, 71% in older) Injection site redness Injection site swelling Localized lymph node (gland) swelling (0.3%)

Generally resolved within a few days

Injection site pain (86%)
Injection site redness
Injection site swelling
Localized lymph node (gland) swelling

0.8% had a delayed local reaction (8 days or more after the shot was given)

Mean duration 2.6 days

Systemic Reactions

Headache Fatigue
Muscle pain Joint pain
Chills Nausea/vomiting

Generally resolved within a few days

Headache Fatigue
Muscle pain Joint pain
Chills Nausea/vomiting

Mean duration 3.2 days

After the 2nd Shot

Local reactions were noted to be slightly lower

Systemic reactions were noted to be higher

Systemic reactions were noted to be more common in younger subjects (less than 55 years old)

Systemic reactions were noted to be higher after the second shot

Systemic reactions were noted to be more common in younger subjects (less than 65 years old)

Hyper- sensitivity (Allergic-like) Reactions


1.5% Vaccine Group vs 1.1% Placebo Group

Other Notable Reactions

No COVID-19 related deaths occurred

4 Vaccine Related Severe Adverse Reactions in the Vaccine Group – Shoulder injury, Axillary gland swelling, arrhythmia, leg numbness/tingling

1 COVID-19 related death occurred in the Placebo Group

Bell’s Palsy- 3 people in Vaccine group (<0.1%) vs 1 person in the Placebo Group (<0.1%)

No vaccine-enhanced respiratory disease occurred in the Vaccine Group