Public Health

Pfizer vs. Moderna COVID Vaccine - How are they different?

Khang T. Vuong, MHA30 Dec 2020

The COVID vaccine front runners in the United States are currently Pfizer-BioNTech and the biotechnology company Moderna. Pfizer’s vaccine has been granted emergency use authorization by the Food and Drug Administration and health care workers already started receiving the vaccine. Moderna’s vaccine may be approved this week. Due to increased funding from operation warp speed, the vaccine development process was able to be highly expedited. In this guide, we explain the difference between Moderna and Pfizer COVID vaccines. 

Moderna vs Pfizer vaccine effectiveness in different groups:

Overall effectiveness: Pfizer’s phase three clinical trial included 43,000 participants, half of which got the vaccine. There were 162 cases of COVID-19 in the placebo group and 8 in the vaccine group. Therefore, the vaccine was 95% effective in protecting against COVID-19. 

Moderna’s phase three clinical trial included 30,000 participants, half of which got the vaccine. There were 185 cases of COVID-19 in the placebo group and 11 in the vaccine group. Therefore, Moderna announced that its vaccine was 94.1% effective in protecting against COVID-19. 

Older adults: Pfizer’s vaccine was 93.7% effective in people aged 57 and above. Moderna’s vaccine was 100% effective in people aged 65 and above. 

People with pre-existing conditions: Both Moderna and Pfizer vaccines were tested on people with pre-existing conditions, such as diabetes, lung disease, heart disease, HIV and obesity. Moderna’s vaccine was 95.9% effective in this group and Pfizer’s vaccine was 95.3% effective. 

Men vs women: Both vaccines were about 95% effective in men and a little over 93% effective in women.

Type of vaccine: 

Both Pfizer and Moderna created vaccines that use genetic material from the virus, or mRNA (messenger RNA). mRNA vaccines give instructions for our cells to make a spike protein. That protein is recognized by our immune system, which triggers an innate immune response and the production of antibodies. mRNA vaccines do not affect our DNA at all; in fact, they do not even enter the nucleus of our cells, which is where our DNA is stored. 

The structure of the mRNA molecules used in the Pfizer and Moderna vaccines are different. That’s why the vaccines require different storage temperatures. 

The number of doses: 

Both the Pfizer and Moderna vaccines require two doses in order to be effective. It is essential that both doses of the vaccine are taken. 

The doses of the Pfizer vaccine must be taken 21 days (3 weeks) apart. The doses of the Moderna vaccine must be taken 28 days (4 weeks) apart. 

Dr. Ramin Ahmadi, MD, MPH, explains why we need to get two doses of the vaccine. According to Dr. Ahmadi, “During the vaccine study phase, the majority of the recipients developed the neutralizing antibody after the second dose. 

Developing critical antibodies is only one part of immunity against the virus. Memory cells and other immune cells also have to be recruited and developed. While it is possible to become immune after one dose, the second dose ensures that the body has developed the necessary immunity for increased efficacy.”


Pfizer’s vaccine must be stored at -94 degrees Fahrenheit. Therefore, this vaccine must be transported using special storage and dry ice to maintain the necessary temperature. At 25 degrees Fahrenheit, the Pfizer vaccine can last 5 days. 

Moderna’s vaccine must be stored at -4 degrees Fahrenheit. At 25 degrees Fahrenheit, the Moderna vaccine can last 1 month. Because the Moderna vaccine can be stored at warmer temperatures, it may be a better option for more rural areas of the country. 


Pfizer’s vaccine has been bought by the U.S. government for $19.50 per dose. Since two doses are needed, the vaccine will cost $39 per person. 

Moderna noted that the cost of its vaccine will be anywhere from $32-37 per dose. Since two doses are needed, the vaccine will cost $64-72 per person. 

Most private insurance companies, Medicaid, and Medicare will cover the cost of the vaccine. If you do not have insurance, there will likely be locations where you can access the vaccine for free. However, you may need to pay fees to cover the administration of the vaccine and the cost of storage. See our article for more information on the price of the COVID-19 vaccines. 

Side Effects Pfizer vs. Moderna: 

Some people who took the Pfizer and Moderna vaccines experienced mild reactions. Below are the most commonly reported vaccine 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%

It seems as if most participants were able to recover within 1-2 days after receiving the injection and did not experience symptoms after that. It is important to note that these side effects are commonly reported after receiving other vaccines as well, such as Shingrix.

Dr. Ahmadi explains that “every good vaccine stimulates the immune system. During the course of this stimulation, some inflammatory substances are released in the body and cause symptoms like aches, fatigue, or fever.” 

Timeline for approval:

Pfizer was granted emergency use authorization from the FDA last week. Many health care providers and people in nursing homes already began receiving the vaccine. Only people over the age of 16 can get this vaccine for the time being.

Moderna filed for EUA on November 30th, 2020. The FDA will be reviewing Moderna’s request on December 17th, 2020. If Moderna’s vaccine is approved, it can start being administered to people over the age of 18 this weekend. 

Will I get to choose if I want the Pfizer-BioNTech or Moderna coronavirus vaccine? It's not likely

If Moderna and Pfizer’s vaccines are approved in the coming weeks, we will likely not be able to choose which vaccine we want to get. There are not currently enough supplies to vaccinate everyone in the U.S., so for the next few months, we will just have to take whatever vaccine we can get. 

By the second half of 2021, there will likely be more vaccines on the market and greater supplies available. At that point, we may be able to choose between several vaccine options. 

Will there be other coronavirus vaccines available soon? 

While Moderna and Pfizer are likely to be the first to get a vaccine approved, others are vaccine candidates following close behind. 

On November 23rd, AstraZeneca released promising results from its COVID-19 vaccine trials. When participants were given half a dose of the vaccine followed by a full dose one month later, the vaccine was 90% effective in preventing COVID-19. However, when participants were given two full doses, the vaccine was only 62% effective in preventing COVID-19. Follow-up studies are being completed to determine the most effective dosages. 

In addition, Johnson & Johnson is currently enrolling participants for a phase three trial. They are going to be testing the efficacy of both one and two doses of the vaccine. 

We will likely see the approval of several other vaccines over the next year. There are currently 13 vaccines in phase 3 clinical trials, 17 vaccines in phase 2 clinical trials, and 41 vaccines in phase 1 clinical trials. 


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