A new study shows the first shot alone of the Pfizer vaccine can be 85% effective in preventing symptomatic COVID-19.
That's according to an Israeli study published in the Lancet medical journal.
The findings could push countries to delay giving out the second dose until more people get the first one.
The study also found that the vaccine can be stored in regular freezers. When it first rolled out, a major concern was transferring it because it needed to be stored at super-cold temperatures.
Pfizer says it's working to get permission from the FDA to change the vaccine's storage rules.