Amazon workers can take unlimited sick days this month - but only those in quarantine for the Covid-19 virus will be entitled to extra sick pay.
Many US warehouse workers are entitled to only 10 days' leave a year - for all holidays, sickness and emergencies.
And some had asked Amazon to change its policy to stop coronavirus spreading.
Some workers also say they are being told increase their hours, known as mandatory extra time, because of increased demand and staff shortages.
In a blog, Amazon said: "The health and safety of our employees and contractors around the world continues to be our top priority as we face the challenges associated with Covid-19.
"Effective immediately, all Amazon employees diagnosed with Covid-19 or placed into quarantine will receive up to two weeks of pay.
"This additional pay while away from work is to ensure employees have the time they need to return to good health without the worry of lost pay.
"This is in addition to unlimited unpaid time off for all hourly employees through the end of March."
Amazon has also established a $25m (£19.6m) fund to support independent delivery service partners and their drivers, Amazon Flex participants and seasonal employees "under financial distress".