For starters, a COVID-19 vaccine can be released if it's 'safe and proves effective' on as few as 50% of those who receive it, according to recently released federal guidelines. What's more, the definition of "effective" means that it simply has to 'minimize the most serious symptoms,' according to the report.

"We should anticipate the SARS-CoV-2 vaccine to be similar to the influenza vaccine," said Dr. Kathleen Neuzil, director of the Center for Vaccine Development at the University of Maryland. "That vaccine may or may not keep people from being infected with the virus, but it does keep people out of the hospital and the ICU."

Because of this, experts say that the first round of COVID-19 vaccines probably won't eliminate the need for masks, social distancing and other measures. So – after all the promises made by government officials, a vaccine may only reduce symptoms, and may turn into a recurring shot that only works on half the population.