(Reuters) - Amazon.com Inc is rolling out on-site COVID-19 vaccination for its U.S. front-line employees, it said on Thursday, as companies step up efforts to get their workers immunized against the coronavirus. The e-commerce company, which has also been testing employees for COVID-19, said that on-site vaccination programs would first start in Missouri, Nevada, and Kansas and then expand across the country as more vaccines become available. Amazon will give up to $80 to front-line workers with no access to the on-site clinics, mirroring a move by companies such as hotel operator Marriott International Inc and retailer Kroger Co to provide employees incentives to get COVID-19 vaccines. Earlier in December, Amazon had asked the U.S. government to prioritize essential workers, including its warehouse, grocery store and data center staff, for receipt of the COVID-19 vaccine. (reut.rs/31wnzqB)