COVID-19 Vaccine FAQ


Now that vaccines for COVID-19 have been available for several months, roughly one-third of Mohave County residents have been vaccinated. Certain people cannot get vaccinated, including those with allergies to any components, and kids under 12. For everyone else, deciding whether to get vaccinated is a very personal choice. It is important to have accurate, up-to-date information about the current vaccines for COVID-19.

The following frequently asked questions (FAQs) are compiled from sources such as peer-reviewed journals, the Centers for Disease Control and Prevention (CDC), the U.S. Food and Drug Administration (FDA), and the Arizona Department of Public Health (further reading and references are included at the end).

Why should I consider getting vaccinated against COVID-19?

The COVID-19 vaccine creates an immune response in your body that will help keep you from getting sick with COVID-19.  Importantly, the vaccines can help prevent severe illness with COVID, greatly reducing your risk of hospitalization and death.  
The more our population is protected from getting sick, the less chance COVID will spread from person to person in our community.  Getting the vaccine can help bring an end to the pandemic.

What COVID-19 vaccines are available?

Multiple COVID-19 vaccines are in various phases of testing and development in the United States and worldwide.  At this time, the U.S. Food and Drug Administration (FDA) has granted Emergency Use Authorization* for the following vaccines:

Moderna (mRNA-1273) ― Two doses given at least 28 days apart
Pfizer/BioNTech (BNT162b2) ― Two doses given at least 21 days apart
Johnson & Johnson (Janssen) – Single dose   

* FDA’s Emergency Use Authorization (EUA) is a process that helps facilitate the availability and use of medicines and vaccines during public health emergencies, such as the current COVID-19 pandemic.

How do the vaccines work?

mRNA

Both Moderna and Pfizer are messenger RNA (mRNA) vaccines, which are different from vaccines developed in the past. They contain a strand of mRNA instead of a weakened virus to generate an immune response in your body.

Essentially, the mRNA in the vaccine is a set of instructions that directs your cells to make a spike protein that mimics the SARS-CoV-2 virus. Your immune system recognizes that protein as a threat and will begin to make antibodies. Those antibodies will protect you from getting infected if the real SARS-CoV-2 enters your body.

Scientists have studied mRNA technology for decades in vaccine trials for influenza, Zika, rabies, and cytomegalovirus. Beyond vaccines, mRNA has been used in cancer treatment research to trigger the immune system to target specific cancer cells.

Once the technology showed promise against COVID-19 in the laboratory, the U.S. government fast-tracked mRNA vaccines for testing and development.

Viral Vector

Johnson & Johnson’s Janssen vaccine also teaches your cells to make the spike protein using a different mechanism. Instead of using mRNA, this vaccine uses a modified version of a different virus (not SARS-CoV-2) as a vector to enter a cell and produce the spike protein. This triggers a similar immune response, teaching your body how to fight the virus that causes COVID-19.

Did COVID-19 vaccines bypass safety testing?

No. The COVID-19 vaccines are held to the same rigorous safety standards as all other vaccines. All authorized COVID vaccines underwent FDA’s mandatory clinical trial process for evaluating vaccine safety and efficacy.

Fast-tracking the vaccines was possible because researchers used existing clinical trial networks (like those that are currently studying HIV treatments and vaccines) to quickly conduct the COVID-19 vaccine trials.

The FDA and CDC prioritized review of the clinical trial data by scientists and clinicians within their respective agencies and by the independent Advisory Committee on Immunization Practices (ACIP).  All safety criteria were met to obtain FDA Emergency Use Authorization.

It was also possible to fast-track vaccine production because, unlike conventional vaccines, manufacturing mRNA vaccines is a much shorter process.

For example, most vaccines for viral diseases are made from viruses grown in chicken eggs or mammalian cells. The process of collecting the viruses and adapting them to grow in a laboratory can take many months.

Conversely, mRNA is made from an RNA template in a laboratory using readily available materials. The template can be shared by scientists and manufacturers across the globe and then quickly produced using polymerase chain reactions (a laboratory technique used to make multiple copies of a segment of RNA). Currently it takes about a week to generate an experimental batch of mRNA vaccine.

Lastly, the vaccines were rolled out in record time because the U.S. government and vaccine manufacturers invested millions of dollars to scale up vaccine production while the clinical trials were in progress, which greatly reduced the amount of time between vaccine authorization and vaccine implementation. Investment in manufacturing normally doesn’t happen until later in the vaccine development process because of the financial risk.

How were COVID-19 vaccines tested for safety?

The COVID-19 vaccines currently in use were tested through the following clinical trial phases, which are standard for testing all vaccines. Safety data is collected and reviewed in all the phases of the clinical trial.

In the first phase, small groups of people (between 20 and 100) are enrolled. Researchers try to answer questions like:

  • Is this vaccine safe?
  • Are there any serious side effects?
  • How does the vaccine dose relate to any side effects?
  • Is the vaccine causing an immune response?

The second phase involves several hundred volunteers.  Researchers try to answer questions like:         

  • What are the most common short-term side effects?     
  • What’s the body’s immune response?
  • Are there signs that the vaccine is protective against the disease?

The third phase enrolls a thousand or more volunteers.  Researchers try to answer questions like:

  • How do disease rates compare between people who get the vaccine and those who do not?
  • How well can the vaccine protect people from disease?
  1. More than 30,000 volunteers were enrolled in Phase 3 of the Moderna COVID-19 vaccine trials, and over 25,000 received both doses. The Moderna vaccine trials were conducted at approximately 100 sites across the United States.
  2. More than 45,000 volunteers were enrolled in Phase 3 of the Pfizer COVID-19 vaccine trial. More than 43,000 volunteers received both doses. The vaccine trials were conducted at approximately 150 sites domestically and internationally, and 39 U.S. states are represented in the study.
  3. More than 44,000 volunteers were enrolled in Phase 3 of the Janssen vaccine trials, which included the United States, Mexico, and South Africa as well as several South American countries.

Data from the clinical trials show that the vaccines are safe and effective at preventing COVID-19 (see peer-reviewed scientific papers listed below).

The following are important conclusions from the trials:

  • The clinical trials did not reveal any significant safety concerns; however, a small number of severe allergic reactions have been reported. Therefore, recommendations for observation after vaccination include monitoring for 15 or 30 minutes.
  • Both mRNA vaccines are approximately 95% effective at preventing COVID-19 disease.
  • The Janssen vaccine was 66.3% effective in clinical trials at preventing laboratory-confirmed COVID-19 infection. It also showed in clinical trials to be 100% effective at preventing hospitalization for COVID-19 four weeks after immunization.  
  • The vaccines often produce symptoms after vaccination, especially after the 2nd dose. Side effects may include fever, headache, fatigue, and muscle aches. Side effects are an indication of a good immune response—so while they may be unpleasant, it means the vaccine is doing its job. ​ The side effects are generally short-lived, and most people feel better within a day or two. ​

Will researchers continue to monitor COVID-19 vaccine safety?

As of July 2021, more than 335 million doses of COVID-19 vaccines have been given in the United States. Monitoring vaccine safety is a regular, ongoing part of vaccine development.

For example, earlier this year, the FDA and CDC recommended a pause in the use of the Johnson & Johnson vaccine to investigate rare blood clots that had occurred among vaccinated individuals. The pause was lifted after thorough research showed the potential benefits of the vaccine outweighed the potential risks.  

Systems have been in place for decades to ensure the safety of routine vaccines. These systems are complementary and work together to monitor vaccine safety.

These include:

  • The Vaccine Adverse Event Reporting System (VAERS), which collects and analyzes reports of adverse events that happen after vaccination.
  • The Vaccine Safety Datalink and the Post-Licensure Rapid Immunization Safety Monitoring System, which are networks of healthcare organizations that actively analyze the healthcare information of millions of people.
  • 1The Clinical Immunization Safety Assessment (CISA), which is a collaboration between CDC and 7 medical research centers. CISA assists healthcare providers with complex vaccine safety questions and conducts clinical research studies to better understand vaccine safety.
  • FDA’s Biologics Effectiveness and Safety System (BEST), which is a system of electronic health record, administrative, and claims-based data for active surveillance and research.

These existing data systems can rapidly detect signals for possible vaccine safety problems.
Additional systems and data sources are also being developed to further enhance safety monitoring capabilities. One example is V-safe—an active surveillance system that uses text messaging to initiate web-based survey monitoring.

Does the COVID-19 vaccine affect your DNA?

No. This is a common myth about COVID vaccines. Neither mRNA nor viral vector vaccines interact with your DNA in any way. Both types of vaccines deliver genetic material to signal your cells to launch an immune response. This material does not enter the cell’s nucleus, where our DNA is. Once that message is delivered, the body gets rid of the components of the vaccine.

Can the vaccine give you COVID-19?

No. COVID-19 vaccines will not give you COVID-19. None of the COVID-19 vaccines currently in use in the United States contain the live virus that causes COVID-19. However, after getting the vaccine, people can experience such side effects as fever, headache, fatigue, and muscle aches. For vaccines with two doses, the side effects are typically more severe following the second shot. This is because the first shot primes the immune system, helping it recognize the virus, and the second shot strengthens the immune response.

Will the vaccine cause you to test positive on COVID-19 diagnostic tests?

No. COVID-19 vaccines won’t cause you to test positive for the virus with diagnostic testing (e.g., PCR test). However, there is a possibility you could test positive on some antibody tests. Antibody tests can indicate your body has developed an immune response (antibodies) and that you may have some level of protection against the virus, which is the goal of vaccination.

Should people get the vaccine if they already had COVID-19?

Yes. At this time, experts do not know how long someone is protected from getting sick after recovering from COVID-19. The immunity someone gains from having an infection, called “natural immunity,” varies from person to person. Until more data becomes available, the vaccine is currently recommended for people who have recovered from COVID-19.

How long are people immune after getting the COVID-19 vaccine?

We won’t know how long immunity produced by vaccination lasts until we have more data over time. Researchers will continue to study both natural immunity and vaccine-induced immunity to COVID-19.

Where can I get more information?

The following resources and links provide detailed information regarding COVID-19 vaccines:

U.S. Centers for Disease Control (CDC) Covid-19 vaccination resources for Healthcare Workers

Federal Drug Administration (FDA) regulatory process for facilitating the development of COVID-19 vaccines

Arizona Department of Health Services COVID-19 vaccine information

Moderna COVID-19 vaccine trial overview

Pfizer-Biontech COVID-19 vaccine trial overview

Johnson & Johnson vaccine information

The following pdf reports include peer-reviewed evidence supporting the use of mRNA vaccination technology for COVID-19:

Jackson et al 2020: The preliminary Phase 1 report for Moderna

Baden et al 2021: A safety and efficacy report for Moderna

Polack et al 2020: The Safety and Efficacy reports for Pfizer

Widge et al 2021: An assessment of the lasting Immune response and predicted lasting protection against Covid.

Wang et al 2021: A Full characterization of vaccine recipient immune responses.