BOSTON (CBS) – The pharmaceutical company AstraZeneca said Monday that late-stage trials show its COVID-19 vaccine is up to 90-percent effective.

This vaccine was developed by researchers at Oxford University and manufactured by AstraZeneca. In a phase 3 clinical trial, they found the vaccine was 90-percent effective when volunteers were given a half-dose of the vaccine then a full dose one month later.

When two full doses were given one month apart, the efficacy was only 60-percent.

It’s unclear why a smaller first dose may be more effective, but combining those two outcomes, they’re saying the vaccine is on average 70-percent effective.

This vaccine doesn’t require special storage conditions, unlike the Moderna and Pfizer vaccines. Those two vaccines need to be stored long-term in very low temperatures. The AstraZeneca vaccine can be refrigerated, which is how most standard vaccines are stored. That would make worldwide distribution a lot easier than a vaccine that requires special freezers.

Here are some questions to consider going forward:

How does this vaccine work compare to the Pfizer and Moderna vaccines?

The Pfizer and Moderna vaccines use a small piece of genetic material from the coronavirus to stimulate the immune system. The AstraZeneca vaccine uses a weakened form of a common cold virus combined with genetic material from the spike protein of the coronavirus to stimulate the immune system to recognize the coronavirus as an enemy invader.

What’s next for the AstraZeneca vaccine?

The clinical trials will continue. In the meantime, the company plans to apply for emergency use authorization in countries that require it and produce up to 3 billion doses of vaccine in 2021.

When it comes time to get vaccinated, how will people know which vaccine is best?

The results that have been reported for these three vaccines are preliminary and may change as the trials continue. We have always known that it would take more than one company and more than one vaccine to vaccinate the world’s population. We now have three vaccines that appear to be safe and effective, and there are more on the horizon. When it comes time for you and your family to get immunized, it will be with a vaccine that is deemed both safe and effective.

Dr. Mallika Marshall