Photo ofdoctor in gloves holding syringe and making injection to senior patient in medical mask. Covid-19 or coronavirus vaccine

We will update this post as news comes out about COVID-19 vaccines. This post was last updated on July 27, 2021. Many of the questions and answers below come from our Jan. 20, 2021 webinar, “COVID-19 Vaccine: Allergy, Anaphylaxis and Answers.”

Are vaccines effective?

Absolutely! Vaccines save lives. They are one of the greatest public health achievements of the 20th century.

What are the benefits to the COVID-19 vaccine?

COVID-19 can be a very serious illness. The vaccines have been shown to be highly effective in preventing the virus. They allow your body to develop immunity to the virus without getting sick. If someone who is vaccinated does get diagnosed with COVID-19, they are much less likely to experience severe illness.

It is also believed that getting vaccinated protects people around you as well. Getting sick with COVID-19 provides a level of immunity, but how long is unknown. And the illness brings risk of severe symptoms or death. Thus, developing immunity through vaccination is the safest choice.

Photo of COVID SDM Graphic

How many COVID-19 vaccines are available?

As of April 2021, there are three COVID-19 vaccines available in the United States for people ages 12 and up:

  1. Pfizer/BioNTech
  2. Moderna
  3. Johnson & Johnson

As of April 23, 2021, the CDC and FDA are lifting the pause they put on distribution of the Johnson & Johnson vaccine. Both agencies recommended a pause on April 13 due to the occurrence of blood clots in a very small number of people (6 cases out of 6.8 million doses) who received the vaccine. Healthcare professionals who administer the vaccine will be given updated fact sheets with information on how to diagnose and treat people if blood clots occur after vaccination. People who receive the Johnson & Johnson vaccine will also be given fact sheets addressing symptoms.

What types of COVID-19 vaccines are there?

Messenger RNA (mRNA) vaccines

The mRNA vaccines do not contain the live virus, but rather a synthetic material that mimics the virus. This sends your body a message to produce antibodies and t-cells that build up an immune system defense. It protects people from getting infected when exposed to the real virus.

Vector vaccines

Viral vector vaccines use a common cold virus as a vector with genetic code from COVID-19 introduced into it. The vaccine delivers the genetic code to our cells and trains our immune system to protect itself from future infections. The vaccine does not contain a live virus. It cannot cause an infection from either COVID-19 or the vector virus.

How effective are the COVID-19 vaccines?

The Pfizer/BioNTech vaccine is reported to be 95% effective in preventing symptomatic illness. The Moderna vaccine is reported to be 94.5% effective in preventing symptomatic illness.

The Johnson & Johnson vaccine is reported to be 66% effective in preventing moderate to severe COVID-19, and 85% effective in preventing severe or critical disease.

What should I know about the Pfizer/BioNTech vaccine?

  • First vaccine to receive emergency use authorization
  • mRNA vaccine
  • Only vaccine currently available for 12-16 age group
  • 2 doses, 3 weeks apart
  • Ingredients
  • Potential for side effects:
    • Pain at injection site
    • Flu-like symptoms
  • Must be stored very cold (-70 degrees F), making it less accessible for smaller facilities.

What should I know about the Moderna vaccine?

  • mRNA vaccine
  • 2 doses, 4 weeks apart
  • Ingredients
  • Slightly more effective in younger people than older people
  • Potential for side effects
    • Pain at injection site
    • Flu-like symptoms
  • Can be stored at 36 degrees F to 46 degrees F, making it more accessible

What should I know about the Johnson & Johnson vaccine?

  • Vector vaccine
  • Approved as a single dose
  • Ingredients
  • May be more effective against COVID-19 variants that have surfaced around the world
  • Potential for side effects
    • Pain at injection site
    • Flu-like symptoms
  • Can be stored in refrigerated temperatures and not in a freezer, making it more accessible and easier to transport

Are there other COVID-19 vaccines likely to be available soon?


  • Vector vaccine
  • 90% effective when half dose is given.
  • 2 doses, 1 month apart
  • Does not require special cooling.

Who gets the vaccine and when?

The vaccine will be administered in phases. See the chart below:

Chart on COVID Vaccine Allergies

What are the side effects of the COVID-19 vaccines?

The COVID-19 vaccine may cause:

  • Pain and/or swelling at the injection site.
  • Fever
  • Chills
  • Fatigue
  • Headache

These symptoms are normal as the body works to build immunity to the virus.

How can COVID-19 vaccine side effects be managed?

Not everyone will develop side effects from the COVID-19 vaccine. If you do have side effects, there are things you can do to minimize the symptoms including:

  • Using a cool, wet and clean towel over the injection site
  • Moving the affected arm
  • For fever – drink lots of fluids and wear light clothing
  • Even if you have side effects from the Pfizer/BioNTech and Moderna vaccines, it is important you get the second dose unless your doctor advises against it due to the risk of an allergic reaction to the vaccine ingredients.

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Should you take pain relief medications such as Tylenol or Motrin before getting the COVID-19 vaccination?

  • The U.S. Centers for Disease Control and Prevention (CDC) does not recommend taking pain relief medication before vaccination. It is unknown if those medications will decrease the effectiveness of the vaccine.
  • For pain, discomfort or fever after the vaccine, you may take these medicines as long as you have no medical reason to avoid them.

Do I need to get vaccinated if I already had COVID-19?

People who already had COVID-19 should get the vaccine. While re-infection with COVID-19 is rare, it is possible. Infection does provide some immunity, but it is unknown how long the immunity lasts.

How long should people wait to get the COVID-19 vaccine after having COVID-19?

There is no specific timeframe for vaccination after COVID-19. However, people should wait until they no longer have any symptoms. If someone is treated with monoclonal antibodies, then they should wait 90 days before getting the vaccine. People may also need to wait if they received a vaccine for another disease recently.

Is the COVID-19 vaccine effective against new variants or strains of the virus?

It is common for viruses to mutate over time leading to new variants. There are multiple COVID-19 variants that have emerged over the past several months including ones identified in the United Kingdom, South Africa and Brazil. Thus far, the vaccines available in the United States are effective in producing antibodies to the new variants. However, the vaccines and variants will require ongoing study.

Can you get sick with COVID-19 even after you have been vaccinated?

Yes, people can still catch the virus after getting vaccinated. CDC is calling these “vaccine breakthrough cases.” However, most people who do get COVID-19 post-vaccination develop mild symptoms and are less likely to get hospitalized or die from the virus.

Remember, no vaccine is 100% effective. In clinical trials, the Pfizer/BioNTech vaccine was shown to be 95% effective in preventing symptomatic illness. The Moderna vaccine was shown to be 94.5% effective in preventing symptomatic illness. The Johnson & Johnson vaccine was 66% effective in preventing moderate to severe COVID-19, and 85% effective in preventing severe or critical disease.

What guidelines should be followed after you receive the COVID-19 vaccine?

First off, if you’re getting the Pfizer/BioNTech or Moderna vaccines, it is important that you get both doses of these vaccines. You are not protected until about two weeks after your second shot.

When you are fully vaccinated with a COVID-19 vaccine, it’s important to continue to practice infection prevention measures. This is partly because the vaccines are not 100% effective. Also, it is unknown if people who are vaccinated can still carry and transmit the virus.

So, until enough people are immune it is important that everyone follow guidelines including:

  • Social distancing — 6 feet separation from others
  • Frequent handwashing
  • Wear a mask!

If you are fully vaccinated and exposed to someone with COVID-19, should you still self-quarantine?

People who are fully vaccinated and are exposed to COVID-19 do not need to self-quarantine if they meet conditions established by the CDC:

  • Fully vaccinated – 2 weeks or more since second dose of two-dose vaccine or since first dose of single-dose vaccine
  • Within 3 months of receiving last dose of COVID-19 vaccine
  • No symptoms of COVID-19 since exposure

Is it okay for people with a history of allergies to get the vaccine?

People with a history of allergies or allergic reactions can receive the vaccine. People who are allergic to any of the vaccine’s ingredients or had an allergic reaction to a first dose should not receive the vaccine. They should receive the vaccine at a medical facility where they can be monitored for 30 minutes post-vaccination. Learn more on our COVID-19 Vaccine Allergic Reactions page.

Will antihistamines reduce the antibody response to a vaccine?

There is no data indicating that antihistamines reduce antibody responses. Oral steroids, however, may reduce antibody response.

Are there any medical conditions that may exclude someone from getting the COVID-19 vaccine?

Not currently. People with underlying medical conditions such as asthma or COPD, weakened immune systems, autoimmune conditions, Guillain-Barre syndrome and Bell’s Palsy may receive the mRNA vaccine.

Does taking Tylenol after the vaccine make it less likely to produce an immune response?

No. The only medication that could potentially interfere with the vaccine is oral steroids, which may reduce the antibody response.

Reviewed by Bradley Chipps, MD

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