Pfizer vs. Moderna COVID-19 vaccine: What’s the difference?


ALBANY, N.Y. (NEWS10) — After months of anticipation, the Federal Food and Drug Administration (FDA) approved the emergency use of Pfizer’s COVID-19 vaccine. On December 18 the FDA also approved Moderna’s version for emergency use.

Both vaccines are administered in two doses and have similar effective rates. After the second dose, Pfizer’s vaccine is 95% effective, Moderna’s 94.5% effective but there are many differences.

The Pfizer vaccine is stored at temperatures between -112 to -76 degrees Fahrenheit, is distributed in a five dose vial, and must be diluted with .9% sodium chloride before being administered. The Moderna vaccine is stored at temperatures between -13 to -5 degrees Fahrenheit, is distributed in a ten dose vial and does not have to be diluted before administration.

Pfizer’s vaccine is approved for use in people over the age of 16, the Moderna vaccine will be approved for use in people over the age of 18, according to the FDA’s briefing document. Moderna’s vaccine will also be administered 28 days apart to Pfizers 21 days.

Moderna’s clinical trial had 30,350 participants, Pfizer’s 36,621. The most commonly reported side effect was injection site reaction (84.1%) for the Pfizer COVID-19 vaccine and injection site pain (91.6%) for Moderna’s.

Most commonly reported side effects:


  • Injection site reaction- 84.1%
  • Fatigue- 62.9%
  • Headache- 55.1%
  • Muscle pain- 38.3%
  • Chills- 31.9%
  • Joint pain- 23.6%
  • Fever- 14.2


  • Injection site pain- 91.6%
  • Fatigue- 68.5%
  • Headache- 63%
  • Muscle pain- 59.6%
  • Joint pain- 44.8%
  • Chills 43.4%

The FDA found that side effects were more likely after the second dose. However, severe adverse reactions were reported in between 0-4.6% of participants who were administered the Pfizer vaccine. Between .2-9.7% of participants administered the Moderna vaccine experienced severe adverse reactions.

Clinical trials for both vaccines found older people were also more likely to experience side effects. The FDA said people over the age of 65 were more susceptible to side effects from the Moderna vaccine, and those over the age of 55 more susceptible to side effects from the Pfizer vaccine.

Copyright 2022 Nexstar Media Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

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