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Comparing COVID-19 Vaccines

Comparing the Vaccines

A stylized illustration of a COVID-19 vaccine vial with various related doodles in the background.

While it is tempting to do head-to-head comparisons of the COVID-19 vaccines that have been approved for use in the US, when it comes to medical technology it just doesn’t work like that.

Of the currently available vaccines, two use mRNA technology and one uses technology similar to vaccines we’ve been using for years. The next vaccine likely to be approved for emergency use in the US will also be utilizing familiar technology.

While the world is just now becoming familiar with mRNA medical technology it has been studied for over a decade, with clinical trials that range from vaccines to cancer treatments. So, while it may seem they have been developed quickly, scientists have been working on various types of coronavirus vaccines for decades, with COVID-19 being a variation in the family of coronavirus. All of the approved vaccines have undergone extensive testing and have been proven to be overwhelmingly safe.

mRNA is messenger RNA, which is a strand of genetic material in a special coating that ‘talks’ to the cells in your body and instructs them to create a ‘spike’ protein that is unique to COVID-19.  The initial mRNA strand is broken down by the body, but the ‘spike’ protein triggers the immune system to produce antibodies and memory cells that recognize and respond to that unique protein. The mRNA does not enter our cell’s nucleus and does not interact with our DNA or alter our genetic makeup in any way.

The first vaccine approved for use in the US was the Pfizer-BioNTech (Pfizer) mRNA-based vaccine. Based on testing has been determined to be 95% effective in preventing symptomatic disease and 100% effective in preventing severe disease when given in two doses, 21 days apart. Side effects of this vaccine include pain at the injection site, low-grade fever, chills, headache, and fatigue.

The second approved vaccine was the Moderna vaccine, which is the vaccine currently being used in the Silver Thread Public Health District. This is also an mRNA vaccine and has a 94% effective rate of preventing COVID-19, with a slightly lower efficacy rate of 86% in people aged 65 and older. This vaccine is administered in two doses, 28 days apart. Side effects for this vaccine are similar to those previously described, including pain and swelling at the injection site, low-grade fever, chills, fatigue, and headache.

The latest vaccine approved for emergency use in the US is the Johnson & Johnson (J&J) vaccine, which is a viral vector vaccine, utilizing a modified version of a different virus to deliver genetic instructions to cells to create the spike protein that triggers the immune response. The J&J vaccine is also the only one approved to be administered in one dose. It has a 72% overall efficacy, with an 86% efficacy against severe disease. Side effects from this vaccine are similar to those noted previously but are being reported as less severe than either the Pfizer or the Moderna vaccines.

All the available vaccines are safe and effective in preventing symptomatic disease, in halting the spread of disease, and are invaluable tools in keeping ourselves and our communities safe. When comparing the vaccines, it is important to remember that the right shot for you is the one that is available.

Comparing vaccine efficacy rates is not recommended as ALL currently authorized COVID-19 vaccines afford strong protection against severe COVID-19 disease. We encourage everyone to get whatever vaccine is offered to them at their earliest opportunity.

A full comparison overview of all currently approved vaccines can be found by visiting:

Other sources used were:

Yale Medicine:

Centers for Disease Control:


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