British pharmaceutical giant AstraZeneca (AZN  ) in partnership with Oxford University announced on Monday that late-stage clinical trials for its coronavirus vaccine demonstrated that the drug is highly effective in preventing infections. Results for the trial showed that the vaccine has an average efficacy of 70%, but has the potential to be as much as 90% effective.

AstraZeneca is the third major drug company to report late-state trial data for a coronavirus vaccine, adding to the other highly effective vaccines developed by Pfizer (PFE  )/BioNTech (BTNX  ) and Moderna (MRNA  ), which both demonstrated efficacies of about 95%.

The AstraZeneca vaccine was studied using two different dosing regimens: one where participants were given a half dose of the drug, followed by a full dose administered at least one month apart; and the other were participants were given two full doses at least one month apart. The first dosing regime demonstrated 90% effectiveness, while the second regime showed 62% efficacy.

Researchers combined analysis from both dosing regimens to find an average vaccine effectiveness of 70%. The vaccine's developers do not know why the half-dose-then-full-dose vaccine regime was more effective, but plan to investigate further and find which dosage of the vaccine will produce the most protection. The studies did not report any hospitalizations or severe coronavirus infections in participants that received the vaccine.

The trial results reported on Monday came from studies in the United Kingdom and Brazil that involved 23,000 participants. Of the thousands of volunteers, 11,636 participants received doses of the vaccine, which the rest were given an inert placebo. Overall, there were 131 cases of coronavirus infection during the study. AstraZeneca has not released a breakdown of which group the sick participants belonged to, but noted that those details will be publicly released by Tuesday.

Late-stage trials of AstraZeneca's vaccine are still being conducted in the United States, Japan, Russia, South Africa, Kenya and throughout Latin America. The company also have further clinical trials planned for other European and Asian countries.

The vaccine's efficacy is subject to change as more trial data is gathered and analyzed.

Vaccine Check-Up

AstraZeneca's vaccine differs from its other frontrunners in various ways. The first is its technology. While Pfizer, BioNTech and Moderna have developed their shots using new messenger RNA (mRNA) technology that "trains" an individuals immune system to develop antibodies against the coronavirus to prepare the individual for when they are exposed the the real virus. AstraZeneca's vaccine uses traditional vaccine technology, or a modified common cold virus to carry coronavirus genes into human cells which prepare the immune system for the real coronavirus.

Next, the vaccine is relatively cheaper. Since the beginning of development, Oxford University and AstraZeneca set out not to profit from the vaccine during the pandemic and wanted the vaccine to be equitably distributed. The pair's vaccine costs about $2.50 per dose, based on agreements reached with multiple governments and global health organizations. To compare, Pfizer's/BioNTech's vaccine costs $20 per dose, while Moderna's ranges from $15 to $25 each, based on the agreements that companies have reached with the United States government.

Last, AstraZeneca's vaccine can be stored, distributed and handled at average refrigerator temperatures of 2 to 8 degrees Celsius (36-46 degrees Fahrenheit). Pfizer's/BioNTech's and Moderna's vaccines must be stored at low freezer temperatures, with Pfizer requiring sub zero, ultra cold storage temperatures. AstraZeneca's vaccine can be potentially easier to distribute than other frontrunners, especially in developing countries with poorer health care infrastructures.

All three vaccines still need to be approved by national health regulators before they can be widely distributed globally. Pfizer's/BioNTech's and Moderna's vaccine are expected to be approved by the end of the year. AstraZeneca stated that it will immediately prepare to submit for emergency use authorization with various global health regulators.