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COVID-19 Vaccine

By

Margot L. Savoy

, MD, MPH, Lewis Katz School of Medicine at Temple University

Last full review/revision Jun 2021| Content last modified Dec 2021
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COVID-19 vaccines provide protection against COVID-19 COVID-19 COVID-19 is an acute, sometimes severe, respiratory illness caused by a novel coronavirus SARS-CoV-2. COVID-19 was first reported in late 2019 in Wuhan, China and has since spread extensively... read more . COVID-19 is the disease caused by infection with the SARS-CoV-2 virus. There are multiple COVID-19 vaccines currently in use worldwide; this topic includes only those vaccines currently in use in the US.

In the US, the Pfizer-BioNTech COVID-19 vaccine (mRNA) has been approved for use in people 16 years of age and older by the U.S. Food and Drug Administration (FDA). The Pfizer vaccine also received Emergency Use Authorization (EUA) for children 5 to 15 years of age. Two other vaccines, Moderna COVID-19 vaccine (mRNA) and Johnson & Johnson COVID-19 vaccine (adenovirus vector), also received EUA for people 18 years of age and older.

For more information, see the COVID-19 Advisory Committee on Immunization Practices Vaccine Recommendations, the FDA news release for Pfizer COVID-19 vaccine approval, and the EUA fact sheets for vaccination providers for the Pfizer, Moderna, and Johnson & Johnson vaccines. A summary of changes to the 2021 adult immunization schedule is available here.

Preparations

There are two preparations of RNA vaccines for COVID-19:

  • BNT162b2 (Pfizer)

  • mRNA-1273 (Moderna)

There is one preparation of an adenovirus 26 vector vaccine for COVID-19:

  • Ad26.COV2.S (Johnson & Johnson)

Indications

The Pfizer vaccine has FDA approval for the prevention of COVID-19 in people 16 years of age and older.

The Pfizer vaccine has EUA for the prevention of COVID-19 in people 5 to 15 years of age.

The Moderna vaccine has EUA for the prevention of COVID-19 in people 18 years of age and older.

The Johnson & Johnson vaccine has EUA for the prevention of COVID-19 in people 18 years of age and older.

Contraindications and Precautions

Contraindications for the Pfizer and Moderna vaccines are

  • Severe allergic reaction after a previous dose of either vaccine

  • Severe allergic reaction to a vaccine component

The main contraindication for the Johnson & Johnson vaccine is

  • Severe allergic reaction to a vaccine component

Precautions for all three COVID-19 vaccines are

Appropriate medical treatment to manage immediate allergic reactions must be immediately available in the event an acute anaphylactic reaction occurs after any COVID-19 vaccine is given. COVID-19 vaccine recipients should be monitored for immediate adverse reactions.

Immunocompromised people, including those receiving immunosuppressant therapy, may have a diminished immune response to these vaccines.

A warning has been issued for the Johnson & Johnson vaccine because cases of thrombosis with thrombocytopenia have been reported after vaccination. Reports suggest an increased risk of thrombosis involving the cerebral venous sinuses and other sites (including but not limited to the large blood vessels of the abdomen and the veins of the lower extremities) combined with thrombocytopenia. Symptom onset is about 1 to 2 weeks after vaccination. Most reported cases have occurred in females ages 18 to 49 years; some have been fatal. The use of heparin may be harmful in people with suspected thrombosis with thrombocytopenia following the Johnson & Johnson vaccine; alternative treatments may be needed. Consultation with hematology specialists is strongly recommended.

A warning has been issued for the Pfizer and Moderna vaccines that myocarditis Myocarditis Myocarditis is inflammation of the myocardium with necrosis of cardiac myocytes. Myocarditis may be caused by many disorders (eg, infection, cardiotoxins, drugs, and systemic disorders such... read more Myocarditis and pericarditis Pericarditis Pericarditis is inflammation of the pericardium, often with fluid accumulation. Pericarditis may be caused by many disorders (eg, infection, myocardial infarction, trauma, tumors, metabolic... read more Pericarditis have been reported after the second doses of these vaccines, suggesting there may be an increased risk of these events after vaccination. The observed risk is highest in males 18 to 24 years of age. Vaccine recipients should seek medical attention right away if they have chest pain, shortness of breath, or feelings of having a fast-beating, fluttering, or pounding heart after vaccination.

Dose and Administration

The Pfizer-BioNTech COVID-19 vaccine (mRNA) dose is 0.3 mL (30 mcg) IM, given in a 2-dose series 3 weeks apart, for people 12 years of age and older.

The Pfizer-BioNTech vaccine dose is 0.2 mL (10 mcg) IM, given in a 2-dose series 3 weeks apart, for people 5 to 11 years of age.

The Moderna COVID-19 vaccine (mRNA) dose is 0.5 mL IM, given in a 2-dose series 4 weeks apart.

The Johnson & Johnson COVID-19 vaccine (adenovirus vector) dose is 0.5 mL IM.

An additional primary series dose of the Pfizer or Moderna vaccine has EUA for people with a moderately to severely compromised immune system. This additional dose should be given after an initial 2-dose series is completed. (See COVID-19 Vaccines for Moderately to Severely Immunocompromised People.)

Moderately to severely immunocompromised people 18 years of age and older who received the Johnson & Johnson vaccine should not receive an additional primary dose. However, they should get a booster shot Booster shots COVID-19 vaccines provide protection against COVID-19. COVID-19 is the disease caused by infection with the SARS-CoV-2 virus. There are multiple COVID-19 vaccines currently in use worldwide... read more .

Booster shots

People 18 years of age and older who are fully vaccinated against COVID-19 are eligible for a booster shot (see COVID-19 Vaccine Booster Shots):

  • Booster doses are recommended for all Pfizer and Moderna vaccine recipients age 18 years and older and who completed their initial 2-dose series (or their third primary dose, if immunocompromised) 6 or more months ago.

  • Booster doses are recommended for Johnson & Johnson vaccine recipients who are age 18 years and older and who received their first dose 2 or more months ago.

  • Eligible people may choose to receive a booster dose of any available COVID-19 vaccine (Pfizer, Moderna, or Johnson & Johnson), regardless of which vaccine they initially received.

People 16 and 17 years of age who completed their initial 2-dose series (or their third primary dose, if immunocompromised) of the Pfizer vaccine 6 or more months ago are eligible for a booster dose of the Pfizer vaccine only. Unlike people 18 years of age and older who can choose any available COVID-19 vaccine as a booster shot, only a Pfizer booster shot is available to eligible people 16 and 17 years of age.

People 16 and 17 years of age who received the Moderna or Johnson & Johnson primary dose series are not eligible for a booster shot. (See COVID-19 Vaccine Booster Shots.)

Adverse Effects

The three COVID-19 vaccines have similar adverse effects.

Other adverse effects are common:

  • Injection site pain, swelling, and redness

  • Fatigue

  • Headache

  • Muscle and joint pains

  • Fever and chills

  • Nausea

  • Malaise

  • Lymphadenopathy

Because of the risk of reactive lymphadenopathy after COVID-19 vaccination, health care practitioners should discuss mammography with women who are due for a mammogram and who have recently received COVID-19 vaccination. The Centers for Disease Control and Prevention (CDC) states that some experts recommend getting the mammogram before the vaccine or waiting 4 to 6 weeks after getting the vaccine.

More Information

Drugs Mentioned In This Article

Drug Name Select Trade
No US brand name
No US brand name
No US brand name
DESOXYN
Gammagard S/D
SOLIRIS
ULTOMIRIS
No US brand name
ZOVIRAX
No US brand name
VALTREX
SYNAGIS
DURLAZA
No US brand name
FLUMADINE
RELENZA
TAMIFLU
ADRENALIN
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