COVID-19 Vaccines: FAQs

8 min read  |  December 31, 2020  | 
Disponible en Español |

As the news around COVID-19 vaccines continues, we will add to and update this FAQ.

Answers to these questions have come from and been reviewed and confirmed by a number of experts at the University of Miami Health System, including:

COVID-19 Vaccines – The Efficacy, Safety, and Availability

In general, how do vaccines work?

What they do is teach the immune system to fight it when it comes knocking. In other words, if you get vaccinated, it simply means you’re less likely to get sick. Read more.

How do mRNA vaccines work?

mRNA vaccines carry special genetic material to your cells that contain “instructions” that teach your cells how to make “spike protein” which is unique to the SARS-coV-2 virus.  This harmless protein is then displayed by your cells, which tricks your immune system into making antibodies for the virus.  That way if you are exposed to COVID-19, your body already has the tools it needs to fight it.

Important notes:

  • The mRNA does not ever enter the nucleus of your cells so it does not change your DNA.
  • None of the vaccines work by injecting live virus into your system so there is no way to get COVID-19 from the vaccine.
  • This technology is not brand new. It has been studied for decades.  For example, cancer research has used mRNA vaccines to trigger the immune system to target specific cancer cells.

When will I be able to get a vaccine?

The Pfizer BioNTech vaccine was shipped out to locations across the country the week of December 14. The vaccine will be given in phases by order of priority determined through state regulation:

  1. Frontline health care workers which also includes non-medical personnel such as janitorial and dietary services
  2. Elderly residential patients (nursing home and assisted living facilities)
  3. At-risk population

Your employer or health care provider will contact you if you are eligible to receive the vaccine.

Public health experts expect a vaccine, or vaccines, to be available for the general public by late spring at the earliest. Those receiving it first — in mid to late December — will be healthcare workers, first responders and essential workers. Read more.

Are the vaccines safe?

How do we know if the COVID-19 vaccines are safe?

COVID-19 vaccines were tested in large clinical trials that included tens of thousands of people from a broad spectrum of ages, races, and ethnicities, as well as those with different medical conditions.

After that, the U.S. Federal Drug Administration (FDA) extensively reviews the results to decided whether to authorize emergency use and the Advisory Committee on Immunization Practices (ACIP) considers safety and efficacy data before recommending use.

Going forward the CDC will monitor the safety and side effects through the Vaccine Adverse Event Reporting System (VAERS) which will allow the CDC to detect adverse events and safety problems rapidly  Anyone who gets a vaccine is covered under VAERS monitoring and can submit a report.  Caregivers and healthcare practitioners can also submit reports.

Is the vaccine safe for women who are pregnant or breastfeeding?

Women who are pregnant or breastfeeding should discuss with their physicians the risks and benefits associated with vaccination so they can make an informed decision.

There is no data currently regarding the safety of the vaccine for these groups.

However, the CDC’s guidance highlights two reasons why the vaccine may not pose a threat – it does not contain live virus and that mRNA vaccines degrade quickly and do not enter the nucleus of the cell.

In addition, the CDC is urging everyone who gets the vaccine to download the V-safe app, which includes a follow-up function for pregnant women.

Can older people and children get a vaccine?

Older adults, as well as diverse ethnic and racial participants, have been included in clinical trials. They all display a strong immune reaction.

Children under 18 may not be able to get the vaccine for at least a few months because not enough is known on the safety and efficacy of the vaccines for this age group.  Only adults over the age of 18 were enrolled in the initial vaccine trials. Pfizer BioNTech began enrolling children 12 years and older in October and Moderna announced that they will begin to recruit children for their clinical trials in December.

Who should NOT get the vaccine?

According to the CDC, everyone can get the vaccine but there are certain people who should take “precautions” such as risk assessments or a 30-minute observation period after getting the vaccination.

For instance, if you have ever had a severe allergic reaction (anaphylaxis) to a vaccine or other injectable therapy, the CDC recommends discussing past experiences with your doctor and waiting 30 minutes before you leave to make sure you do not have an allergic reaction.

Other groups like people who have a history of allergies to food or medications or who have moderate or severe acute illness, should also discuss history and concerns with their physician.

What to expect

Can I pick which vaccine I want?

Probably not. At this point, Drs. Carrasquillo and Doblecki-Lewis expect several might be available, depending on where you live and the FDA’s approval process. “We will need many different vaccines going into full production to be able to have everyone vaccinated,” Dr. Carrasquillo says.

Why do we need two shots?

Not all COVID-19 vaccines require two shots. AstraZeneca’s and Janssen’s candidates have been tested as one dose. However, a double-dose regimen is required by other vaccines in order to build up strong immunity. This isn’t unusual. The MMR and Shingrex vaccines, for instance, are one shot plus a booster. In contrast, the one-dose flu vaccine changes every year, depending on which strains are the most active that season.

What happens after I get the vaccine?

After you get the vaccine you may feel some side effects, particularly after the 2nd dose.  The most common symptoms are similar to what you may feel after any vaccination and include pain at the injection site, fatigue, headache, fever, and muscle aches.  The side effects are a sign that the vaccine is doing what it is supposed to do and they should subside after a day or two.

You may receive information about how to enroll in v-safe, which is a smart-phone based tool that will check-in with periodically with surveys on how you are feeling. These will occur daily for first week, weekly for 6 weeks, then 3, 6, and 12 months.  The tool will also remind you when it is time for your second dose and resets after the second dose.

How long will immunity last?

We don’t know — but experts say we should count on a booster requirement in the future because immunity may be finite.

I had COVID-19. Do I need a vaccine?

Doctors don’t know yet how protective having a past COVID-19 infection is. Though there have been reported cases of reinfection, “we know antibodies do last at least several months,” says Dr. Carrasquillo.  Those who haven’t contracted the virus may be the highest priority but moving forward, experts will likely recommend all of us to get a vaccine annually.

Will I have a reaction to the vaccine?

You might, but that’s normal. In general, reactions to inoculations tend to the mild, usually a sore arm with some patients reporting a low-grade fever and achiness. Symptoms display within 24 to 36 hours. But that’s a good thing. “It’s your immune system reacting,” says Dr. Doblecki-Lewis. In general severe reactions to immunizations are very rare.

Why do I have to continue with physical distancing and masking after I am vaccinated?

Even after the second dose, it still takes time for your body to develop full immunity, says Dr. Weiss.  Also, while the results have shown the vaccines to be effective at keeping people from getting the COVID-19 illness, we do not yet know if it keeps you from transmitting the virus to someone else.

How long before we can return to normal life?

Hard to tell at this point, doctors say. But researchers estimate between 50 to 70% of the community must be vaccinated to achieve herd immunity, and that will take time. So mask-wearing, hand-washing, and physical distancing are still essential to stop the spread.

A record-breaking timeframe

Vaccines usually take 10 to 15 years to develop. How were drug manufacturers able to rush COVID-19 vaccines to market in less than a year?

There are a few reasons why the COVID-19 vaccine will be available so quickly:

  • Researchers were able to use existing vaccine and treatment clinical trial networks so they could quickly begin conducting vaccine trials.
  • Often, vaccine production is does not happen until much later in the development process because of the financial risk to companies. With the COVID-19 vaccine, manufacturers and the U.S. government invested money to be able to scale up production quickly.
  • mRNA vaccines are faster to produce than traditional vaccines.
  • With other new medical treatments, manufacturers must wait till its their “turn” for review, approval and recommendation. The CDC and FDA are prioritizing the COVID-19 for this process.

How many people were in the Pfizer /BioNTech and Moderna vaccine trials?


  • 43,931 enrolled
  • 45% ages 56-85
  • Racial/ethnic distribution
    • 13% – Hispanic
    • 10% – African American
    • 6% – Asian
    • 1% – Native American


  • 30,000 enrolled
  • Racial/ethnic distribution
    • 63% – White
    • 20% – Hispanic
    • 10% – African American/Black
    • 4% – Asian
    • 3% – All others
  • Age distribution
    • 64% ages 45 and older
    • 39% ages 45-64
    • 25% ages 65+

Contributors Ana Veciana-Suarez and Natasha Bright compiled this list.

Originally published on: October 30, 2020

Tags: COVID vaccines, covid-19 in Miami

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