A Comparison of AstraZeneca, Pfizer, Moderna and Johnson and Johnson’s Vaccines

What is the mRNA Vaccine?

Table with bottle of vaccines
Image by hakan german from Pixabay

First, let us start by defining the mRNA vaccine. It is a new type of disease-killing drug that trains our cells how to make a protein that will trigger our immune system to fight off the virus. 

At least 40% of Americans have received at least one dose of the COVID-19 vaccine and there are many more waiting for it. Pfizer and Moderna vaccines are currently available in the U.S. and other countries, but there are a few more vaccines that might get authorization for use in the U.S. soon. While you might not get to choose the vaccine that you get for immunization, it is still helpful to know about the different types of vaccines administered in other parts of the world. With this in mind, here is a comparison of the four most prominent vaccines for COVID-19. 


The FDA approved the emergency use authorization of the Pfizer-BioNTech COVID-19 vaccine on December 11, 2020. Being the first authorized vaccine for the coronavirus with an efficacy of 95%, people around the world had high hopes for this mRNA vaccine. While initially there were reservations about the rapid development of an mRNA drug, today, an increasing number of people in the U.S. are willing to get immunization against COVID-19. 

The mRNA vaccine for COVID-19 codes the virus’ spike protein. Once injected, the cells trigger the body’s immune system to recognize the invasion of the virus in the body. In the trials, the vaccine demonstrated an efficacy of 95%. However, the vaccine requires specialized storage that can maintain a temperature of around -94 degrees F. Here is a quick overview of the Pfizer-BioNTech vaccine for COVID-19. 

    • Type: mRNA vaccine
    • Doses: 2 doses, 3 weeks apart
    • Emergency Use Authorization: December 11 2020
    • Efficacy: Around 95% efficacy 

Effectiveness against new variants: Clinical research suggests that the vaccine is quite effective against the new U.K., South African and Latin American variants of the virus. 


Another mRNA vaccine authorized for emergency use by the FDA is Moderna. Like the Pfizer BioNTech vaccine, the Moderna mRNA vaccine has an efficacy of around 95% and got authorization for emergency use on December 18, 2020. However, unlike the Pfizer-BioNTech vaccine, the Moderna vaccine does not require a specialized temperature-controlled environment. Rather it remains stable at 36 to 46 degrees F and can be stored in a standard medical or home use refrigerator for up to 30 days. Moreover, the vaccine can be stored at -4 degrees F for up to six months. Here are some quick facts about the Moderna vaccine for COVID-19.

    • Type: mRNA vaccine
    • Doses: 2 doses, 3-4 weeks apart
    • EUA: December 18 2020
    • Efficacy: Around 95%

AstraZeneca-University of Oxford

The third vaccine that has shown the efficacy of 90% in the clinical trials following the first dose is the AstraZeneca vaccine. The efficacy results were from the trials in the U.K. and Brazil. The two doses were administered at least one month apart. However, after the administration of the second dose, there was a decreased efficacy of 62%. The combined effect of the vaccine is 70%. Moreover, it can be stored at 36-46 degrees F for at least six months and does not require a specialized storage facility. 

But unlike Moderna and Pfizer BioNtech, the Oxford-AstraZeneca vaccine is not an mRNA vaccine. Rather, it is an adenovirus-based vaccine that deploys a replication-deficient viral vector based on a weakened version of the adenovirus, the common cold virus that causes infections among chimpanzees. The vaccine contains the genetic materials of the spike protein. Once the vaccine is administered, the immune system is stimulated to attack the coronavirus. 

However, since the very beginning, this vaccine has been a part of several controversies. From the effectiveness of the vaccine to the side effects and halt in the E.U. countries, there are still concerns about the safety and effectiveness of the Oxford-AstraZeneca drug. The Oxford-AstraZeneca vaccine administration is linked to an immune system response in the form of blood clots. As a result, several European countries have put a halt to the distribution of the AstraZeneca-Oxford vaccine. Here are some brief facts about the Oxford-AstraZeneca vaccine. 

    • Type: Adenovirus-based
    • Doses: 2 doses, at least 28 days apart
    • EUA Date: Not approved for use in the U.S. yet
    • Efficacy: Around 70% (as of now)

Johnson & Johnson

The fourth on the list is the Johnson and Johnson vaccine, which is the only single-dose vaccine on the market. Like the Oxford-AstraZeneca drug, the Johnson and Johnson vaccine is also adenovirus-based with an effectiveness of around 66%. It involves the use of an inactivated common cold virus. During the trials, a single dose brought about a robust immune response and was generally well-tolerated. 

However, the administration of the vaccine is associated with a “rare and severe” type of side effect that clots blood. The blood clots are cerebral venous sinus thrombosis (CVST) that occurs along with another medical condition with low levels of platelets. The side effects are observed among women within six to 13 days after receiving the injection. While the FDA recommended a halt on the use of this vaccine, the pause was lifted on April 23 and the distribution was resumed. 

Type: Adenovirus-based
Doses: Single-dose vaccine
EUA: February 27 2021
Efficacy: Around 66%Conclusion 

Man getting injectionWith these four vaccines for COVID-19 and many others that the world is developing, we are indeed a step closer to bringing this pandemic to an end. But it’s still a long way to go. Till then, continue to follow the COVID-19 safety protocols and stay safe!