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Safety & Efficacy

Are Coronavirus Vaccines Safe? 

Dr. Angela Branche, an infectious disease expert who led clinical trials of coronavirus vaccines, discusses the safety and efficacy of the vaccines, and how they were developed and approved so quickly.

Rigorous Safety Standards

All of the clinical trials for coronavirus vaccines are conducted according to the rigorous standards established by the FDA. This includes safety monitoring and frequent oversight of the trials by independent safety review boards and regulators. 

Once a vaccine is approved for use, the FDA and CDC have many safety monitoring systems in place to watch for possible side effects as vaccines are distributed to the wider population. Learn more about how the CDC is ensuring the safety of coronavirus vaccines in the U.S.

Ensuring Efficacy

The clinical trials for coronavirus vaccines included thousands of study participants from the U.S. and around the world. For example, the Pfizer/BioNTech vaccine study included 44,000 participants, and the AstraZeneca/University of Oxford vaccine study included more than 23,000 participants. 

URMC researchers tested both the Pfizer/BioNTech vaccine and the AstraZeneca/University of Oxford vaccine, and thousands of people from our region volunteered to take part in the studies. These trials determine how well vaccines work and are used by the FDA to review and approve new vaccines. 

Learn more about how the CDC is ensuring COVID-19 vaccines work.

Unprecedented Speed

These vaccines were developed and tested faster than ever before. Many factors, such as scientists’ familiarity with the coronavirus family, advances in technology, and the availability of funds to study and manufacture vaccines, contributed to this swift progress.

Read more about how the world made enormous progress on a COVID-19 vaccine so fast.

Review this chart for more information on the vaccines that may be approved for use in the coming weeks and months.

  Pfizer/BioNTech AstraZeneca Moderna
Tested at URMC Yes Yes No
How It Works The vaccine being tested by Pfizer/BioNTech is a messenger RNA (mRNA) vaccine. Learn more about how mRNA vaccines work. The vaccine developed at the University of Oxford and tested by AstraZeneca is a vector vaccine. Learn more about how vector vaccines work. The vaccine being tested by Moderna is a messenger RNA (mRNA) vaccine. Learn more about how mRNA vaccines work.
Doses 2 doses, 3 weeks apart 2 doses, 3 weeks apart 2 doses, 3 weeks apart
Efficacy Latest study results show that the vaccine is 95% effective in preventing infection. Latest study results show that the vaccine is up to 90% effective in preventing infection depending upon the dosing regimen. Latest study results show that the vaccine is 94.5% effective in preventive infection.
Safety No serious side effects were identified. Common side effects include injection site soreness and low grade fever. No serious safety events related to the vaccine have been confirmed. No significant safety concerns related to the vaccine were reported. Common side effects include injection site pain and fatigue.