Moderna and Pfizer-BioNTech have both developed safe, effective vaccines protecting against severe COVID-19 illness that have received an Emergency Use Authorization (EUA) by the Food and Drug Administration in December. To better understand the differences and similarities between the two vaccines – and what that means for you – please reference the information outlined below.
The two vaccines are virtually identical in most aspects, which include:
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Technology
- Both Moderna and Pfizer vaccines are based on mRNA technology, which shows our bodies how to make the spike protein found in the SARS-Cov-2 virus (and that it uses to invade our cells). If ever infected with the actual virus, the immune system is then triggered to produce antibodies toward it to prevent illness.
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Efficacy
- Both vaccines are approximately 95% effective in preventing COVID-19 illness after two doses.
- No other vaccines should be administered within 14 days prior or after receiving either the Moderna or Pfizer COVID-19 vaccine.
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Safety
- Both vaccines were found to be extremely tolerable, with no serious safety concerns identified in Phase 3 clinical trials.
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Side effects
- Approximately 80% of people may develop a mild local symptom (pain at injection site).
- Some may develop more systemic symptoms (fatigue, body aches, chills, fever, etc.) that subside after approximately 24 hours.
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Second dose requirement and interval
- UW Medicine is scheduling second doses of both the Pfizer and Moderna vaccine at a minimum 24 days after the first dose.
- There is no upper limit to receiving second dose, but the ideal timing is before 28 days since the first dose.
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Full vaccination status
- Patients can be considered fully vaccinated one to two weeks after receiving either vaccine.
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COVID-19 exposure or illness
- If you have had COVID-19 in the past 90 days, you may wait to receive the vaccine until the end of the 90-day period.
- With both vaccines, if you are diagnosed with COVID-19 between doses, you should defer your second dose until your symptoms have completely resolved and your healthcare provider has deemed you are safe to return to work.
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Bell’s Palsy or Guillain-Barre Syndrome (GBS)
- No cases of GBS have been reported with either of the two COVID-19 mRNA vaccines. Per CDC guidance, persons with a history of GBS may receive either of the mRNA vaccines. Similarly, there have not been cases of Bell’s Palsy reported higher than baseline rates among unvaccinated individuals.
There are also a few key differences between the two vaccines:
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Storage
- Pfizer – must be shipped and maintained at -94 degrees Fahrenheit for long-term storage, but can be placed in a refrigerator for up to five days
- Moderna – can be shipped and maintained at a standard freezer temperature of -4 degrees Fahrenheit, and can stay in a refrigerator for up to 30 days
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Dilution
- Pfizer – vial must be thawed and then diluted with saline prior to injection
- Moderna – ready to be administered as is
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Minimum age to vaccinate
- Pfizer – 16 years of age
- Moderna – 18 years of age (however the company has begun testing the vaccine in 12- to 17-year olds)
If you have any other questions, please read the UW Medicine COVID-19 Vaccine FAQ, reach out to your manager or contact the UW Medicine vaccine team at uwm-eoc-vaccines@uw.edu. Employees and students may also call the vaccine hotline at 206.520.8788.
