Britain began the mass-vaccination of its population against COVID-19 on Tuesday, becoming the first Western nation to do so in a global endeavour that poses one of the biggest logistical challenges in peacetime history.

Margaret Keenan, a 90-year-old grandmother from Britain, became the first person in the world to receive the Pfizer vaccine outside of a trial following its rapid clinical approval on Dec. 2.

Pfizer said in November final results from the late-stage trial of its COVID-19 vaccine showed it was 95% effective.

Below are the main details of the vaccine, progress on supply deals and potential approvals:

TYPE

• The vaccine, called BNT162b2, is based on messenger RNA (mRNA) technology, which uses a chemical messenger to instruct cells to make proteins that mimic the outer surface of the new coronavirus, thereby creating immunity.
• mRNA relies on synthetic genes that can be generated and manufactured in weeks, and produced at scale more rapidly than conventional vaccines.
• The new technology has not been approved for any other vaccines so far; Pfizer and BioNTech have already collaborated to develop influenza vaccines based on mRNA.
• The vaccine needs to be kept at minus 70 degrees Celsius (-94 F) or below

DOSAGE AND EXPECTED COST

• Based on the supply deal with the United States, the price tag amounts to $39 for what is likely to be a two-dose course.
• Pfizer has said it will not charge other developed countries a lower price for the vaccine than what the United States will pay.

PROTECTION DURATION

• BioNTech Chief Executive Officer Ugur Sahin has said he is optimistic the immunization effect of the vaccine would last for a year. Scientists do not know how long the effect will last.

PENDING APPROVALS

• India is accelerating its review of Pfizer's vaccine to for emergency use, a senior official said on Dec.7.
• Canadian health authorities could approve the vaccine within the next week, medical officials indicated on Dec. 3.
• The European Medicines Agency said on Dec. 1 that if its experts have received enough data from Pfizer about the vaccine, the agency will complete its reviews by Dec. 29.
• Pfizer and BioNTech submitted approval requests for their vaccine candidates to the European drugs regulator on Dec. 1.
• U.S. FDA granted the vaccine a 'fast track' status in mid-July, and is expected to give more indications of its use this week.
• Pfizer signed a deal worth up to $750 million with BioNTech in March to co-develop the potential vaccine, and it ran clinical trials in April.
• Testing of the vaccine began in the United States in May after trials started in Germany the previous month.

TRIALS

• Trials are continuing globally in 154 locations, including in Germany, Japan, Brazil and in several locations within the United States in participants aged 12 years and older. The global Phase I/II/III trials enrolled about 44,000 volunteers.