Vaccines have different temperature requirements

Pfizer-BioNTech

The vaccine is being shipped in special containers filled with dry ice that can maintain a temperature of fewer than -94 degrees Fahrenheit and must be stored at that temperature.

Vials may be placed in a regular refrigerator for up to five days. The vaccine must be used between 30 minutes and two hours once it’s thawed to room temperature.

Moderna

The vaccine can be shipped and maintained at standard freezer temperatures of -4 degrees Fahrenheit.
Vials may be stored in a standard freezer for up to six months.
The vaccine can stay in a standard refrigerator for up to 30 days. The vaccine must be used within 12 hours once it’s at room temperature.

Preparation varies slightly
Pfizer-BioNTech

Once the vial is thawed, the vaccine must be diluted with saline, which is basically salt water, before it can be injected.

Moderna

This vaccine comes ready to be administered. No dilution required.

Who can take the vaccine?

Pfizer-BioNTech

People 16 years old and older

Moderna

People 18 years old and older

Side effects

Pfizer-BioNTech

The most common side effects were pain at the injection site, followed by tiredness, headache, muscle pain, chills, joint pain, and fever, according to the FDA.

In the United Kingdom, two health care workers reported severe allergic reactions after being vaccinated; two health care workers in Alaska reported a serious allergic reaction after receiving the Pfizer-BioNTech vaccine.

In the U.S. trial, four people who received the vaccine developed Bell’s palsy, which causes usually temporary paralysis in facial muscles

Moderna

The most common side effects were pain at the injection site, followed by tiredness, headache, muscle pain, joint pain, and chills, an FDA analysis found.

Three trial participants who received the vaccine developed Bell’s palsy.

How many shots?

Pfizer-BioNTech

Two shots of the vaccine — 21 days apart — are required for it to be fully effective.

Moderna

Two shots are required, 28 days apart.