Anyone travelling to the Australian Open who previously tested positive to the coronavirus, like Sandgren, must provide additional and detailed medical information as proof they are recovered or no longer infectious.
Three-time Grand Slam champion Murray, now ranked 123rd in the world, had pulled out of the season-opening Delray Beach Open in Florida earlier this month to reduce the risk of contracting COVID-19.
It follows news that former world number 1 Andy Murray had tested positive for COVID-19.
"I have big goals that I want to achieve and I do want to change people's perspectives not just on tennis but on sport and how they approach sport", she said in an interview.
The women qualifiers include two-time Australian Open and Roland Garros doubles champion Timea Babos of Hungary and British player Francesca Jones, who has a rare genetic condition.
Before boarding, competitors must test negative and will undergo a series of tests once in the country, while undergoing a 14-day quarantine period in Melbourne.
Tennis Australia is in the middle of getting 1,200 players and their staff across 15 separate charter flights into Melbourne and Adelaide.
"I look forward to being back on tour next month", Keys wrote.