On Wednesday Dec. 2, the United Kingdom approved the Pfizer vaccine, making the UK first to approve and receive it. Britain’s medicines and healthcare regulator judged the vaccine as safe and ready for the public.

“We have carried out a rigorous scientific assessment of all the available evidence of quality, safety and effectiveness. The public’s safety has always been at the forefront of our minds – safety is our watchword,” Medicines and Healthcare products Regulatory Agency Chief Executive, Dr. June Raine said in a statement.

UK officials ordered 40 million doses of the vaccine. Of the doses, 800,000 may be used within the next week. Due to limited supply, the vaccine first must reach residents of nursing homes and their caregivers along with health-care workers. 

After all front-line medical personnel receive the shot, next in line includes those over 75 years of age, then people 70 or older along with clinically vulnerable individuals. Individuals between the ages of 16-64 with underlying health conditions directly follow and, finally, those 50 years of age and over. Directly after these priority high-risk groups, there will be a second phase of vaccinations for younger groups.

Distribution locations remain undecided. However, the vaccine must be stored at cold temperatures of minus 70 degrees celsius. This may pose a challenge in terms of storage and distribution, making only select hospitals suitable for the first rounds of vaccinations.

Prior to UK approval, the Pfizer and BioNTech vaccine went through several rounds of clinical trials and evidence shows that, after two doses of the vaccine, an efficiency rate higher than 90% occurs a week later, with total immunity after 28 days of initial vaccine.

According to a more recent study, CNN reports that, after three rounds of trials, the vaccine has proven 95% effective with no serious safety concerns. However, minimal side effects including pain at the injection site, fatigue, chills and fever may occur.

As for the U.S., the Food and Drug Administration plans on waiting until Dec. 10 to begin considering the approval of the vaccine. Current projections predict the mass of Americans may receive the vaccine in spring of 2021.

The Pfizer vaccine breaks records with its speedy creation, which only took 10 months to push out. This process historically takes up to 10 years before mass administration to the general public.