Multiple COVID-19 vaccines: What’s the difference?

Archive, March, Month

All vaccines are deemed safe and effective, but how do they differ?

Doctors, researchers and the population as a whole rejoiced when a third COVID-19 vaccine was approved.

More effective vaccines out there mean more vaccinated people means the closer herd immunity is to being achieved and protection against the coronavirus, ending the pandemic.

Both Pfizer and Moderna were granted emergency use authorization just before the end of 2020, with Johnson & Johnson’s vaccine endorsed in February.

Johnson & Johnson was described as a “game-changer” by public health experts because it’s the only vaccine that requires a single shot whereas the others are two-shot vaccines spaced weeks apart.

Most importantly, though, all vaccines have demonstrated that they are safe and effective against the coronavirus.

There are, however, some differences between the vaccines.

How they’re designed

The main difference between the vaccines are in how they’re designed.

Both the Pfizer and Moderna vaccines’ underlying technology uses mRNA, which is genetic material delivered to the cells that triggers a response from the immune system. It’s a process that’s not been used in vaccines before but has been researched for more than a decade.

Johnson & Johnson, though, uses the more traditional approach of an adenovirus. Misconceptions exist that this vaccine injects patients with a weakened form of the virus to trigger an immune response. But the vaccine virus is not related to the coronavirus.

The vaccine virus differs from the COVID-19 virus, but still instructs the body’s immune system on how to defend against and defeat the coronavirus after an exposure.

The virus does not cause an infection, and it does not replicate within the body.

Transportation and storage

One of the largest logistical challenges the mRNA vaccines posed was the fact that they had to be stored at ultra-cold temperatures. And once they were removed from cold storage, they had to be used within a certain time window.

Johnson & Johnson, though, can be stored and transported at standard cold temperatures similar to other vaccines.


When COVID-19 officially became a pandemic, public health experts would have gladly accepted a vaccine that was determined to be 60 percent effective.

The Pfizer and Moderna mRNA vaccines are both more than 90 percent effective, and Johnson & Johnson was shown to be 72 percent effective.

Yet there’s a perception that the Johnson & Johnson vaccine is inferior.

This is not the case. The annual flu shot some years has been shown to be 50 to 60 percent effective, yet the medical community still credits it with helping millions of Americans get through the worst of the flu season (by either avoiding infection after exposure or severe symptoms following an infection).

The Johnson & Johnson vaccine — and the mRNA vaccines — has shown to be effective against COVID-19 by preventing infections and avoiding hospitalizations.


Three vaccines have met the criteria for emergency use authorization by the FDA.

In spite of the misconceptions that the vaccines were rushed, the FDA has deemed them all to be safe and effective. And although there have been some adverse reactions, those incidents are isolated and thoroughly investigated.


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