Differences between Moderna and Pfizer's COVID-19 vaccines

MILWAUKEE (CBS 58) -- The FDA authorized the emergency use of Moderna’s COVID-19 vaccine on Friday, and with Pfizer’s COVID-19 vaccine already being distributed to the area, doctors are breaking down the differences between the two.

While there are some differences, doctors say both Moderna and Pfizer’s vaccines are safe and work equally as well, with nearly 95-percent effectiveness.

“In terms of how they’re working, very, very comparable,” said Dr. William Hartman, UW-Health’s principal investigator for AztraZeneca’s vaccine trial.

Dr. William Hartman says while both the Moderna and Pfizer vaccine are safe, more people report having symptoms with the Moderna vaccine than with the Pfizer vaccine. Doctors still don’t have an explanation as to why just yet.

“More fever and chills, more headaches, muscle aches, things like that. They all resolve within a day or two, but people are reporting that a little bit more often with Moderna,” Dr. Hartman said.

There are also differences in the way each vaccine needs to be stored. The Pfizer vaccine requires ultra-cold storage at minus 70 degrees Celsius, whereas Moderna’s vaccine could be stored at minus 20 Celsius, a temperature of normal freezers.

“That’s important, because it’s going to make it available to a lot more places throughout our country and throughout the world,” added Dr. Hartman.

Moderna and Pfizer’s COVID-19 vaccines both require two doses, and use messenger RNA to create antibodies that would attack the coronavirus if it enters a vaccinated person.

“It’s just a small message that they give into the cells, kind of like passing a note,” Dr. Hartman said.

“They use similar ingredients to help you build an immune response,” said Dr. John Raymond, president and CEO of the Medical College of Wisconsin.

Pfizer’s vaccine has a 21-day wait between the first and second dose, while the Moderna vaccine's waiting period is 28 days.

Beyond Pfizer and Moderna, other companies like AstraZeneca are likely to bring other types of vaccines to the market, with findings expected to be released in February.

“The thinking is that they could be applying for their emergency use authorization sometime in early part of February,” Dr. Hartman said.

Doctors say if your end goal is to protect yourself from COVID-19, it doesn’t matter which vaccine you get.

“If that is your end point, they’re all equally effective, they’re all going to do the job and keep you safe,” added Dr. Hartman.

“It’s so much more important that we build immunity, both as individuals and as community, than exactly which vaccine you take,” said Dr. Raymond.

Whether it’s Moderna, Pfizer or AstraZeneca, doctors say none of these vaccines have the COVID-19 virus in it, which means you cannot get the disease from the vaccine.