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Pfizer vs Moderna vaccines: How do they compare?

(AP Photo/Ted S. Warren, File)

(AP Photo/Ted S. Warren, File)

Published Nov 18, 2020


CAPE TOWN- Two Covid-19

vaccine candidates using similar technology are frontrunners in the race to arrive at a safe and effective vaccine and have been found to be more than 90% effective, according to early data from Phase 3 human trials.

The virus has infected more than 54 million people around the world and killed at least 1.3 million people so far, according to figures compiled by Johns Hopkins University.

Here's how the two top Covid-19 vaccine candidates compare:


Pfizer and BioNTech announced last week that their vaccine candidate was 90% effective in preventing people from infection. Moderna followed shortly after and revealed yesterday that its candidate was almost 95% effective. Researchers behind both vaccines say their trials are ongoing and that the final numbers could change.

Both vaccines use technology known as mRNA, which introduces into the body a messenger sequence that contains the genetic instructions for the vaccinated person's own cells to produce the antigens and generate an immune response.

The Pfizer and Moderna vaccines are currently in phase 3 clinical trials, which have 43 538 and 30 000 participants respectively.

Transport and storage

One of the main differences between the two vaccine candidates is how they need to be stored.

Pfizer vaccine candidate must be kept at around -70 °C during shipment and storage to maintain optimal efficacy.

The Moderna vaccine has been shown to last for up to a month in household fridges, and remains stable for up to six months at -20 °C, which is equal to most household or medical freezers.


The Moderna vaccine is more expensive than the Pfizer vaccine. It was estimated to be for $38 or R585 a dose during the summer - higher than Pfizer, at $20 or R308.

Side effects

Both vaccines, which require two injections, have shown to elicit a few side effects. Moderna’s can result in fatigue, headache, and joint pain; for Pfizer’s, side effects are more flu-like and can include muscle pain and fever.

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