Mission statement explains the company’s reason for existence. It describes the company, what it does and its overall intention. The mission statement supports the vision and serves to communicate purpose and direction to employees, customers, vendors and other stakeholders. The mission can change to reflect a company’s priorities and methods to accomplish its vision.

Vision statement: Describes the organization as it would appear in a future successful state.
Also I think as your company grows and as the competitive environment changes, your mission may require change to include additional or different needs fulfilled.

For example: Philips Healthcare

Mission statement: ” Improving people’s lives trough meaningful innovation.”
Vision:
“At Philips, we strive to make the world healthier and more sustainable through innovation. Our goal is to improve the lives of 3 billion people a year by 2025. We improve the quality of people’s lives through technology-enabled meaningful innovations – as co-creator and strategic partner for the Philips businesses and complementary open innovation ecosystem participants. ”

Philips is one of the greatest companies in Medical Imaging Technology (comes after Siemens),at 2015 Philips improved 2 billion people live,this number verified by marketing intelligence officers, product marketeers, clinical scientists and finally by the Director Sustainability Healthcare of Philips. It seems to be a good number and great success, since Philips mission to improve 3 billion people lives by 2025.

https://www.philips.com/b-dam/corporate/about-philips/sustainability/downloads/ecovision-methodologies/Methodology-for-calculating-Lives-Improved-2016.pdf

https://2015.annualreport.philips.com/#!/improving-peoples-lives