The world is making big changes as it tries to move on from the COVID-19 pandemic. One of them is the closure of the NHS COVID-19 app that prevented about a million cases and saved thousands of lives.

The app, downloaded around 30 million times since it launched in 2020, served as a tool to help people become aware if they got exposed to the virus. But just this Thursday, the app version available in England and Wales stopped working, according to the BBC.

The other versions for Scotland and Northern Ireland had already closed. The app will officially leave the Apple and Google Play stores in May. Before this, the app already sent notifications to its users, informing them of its imminent shutdown.

The app required Bluetooth to identify nearby devices that also had it installed. When a user reported a positive COVID-19 test in the app, alerts would be sent to every user who had been in close contact with that case. User data was shared anonymously, so the cases were not identifiable via the app.

Once users received the alert, they were encouraged to self-isolate to prevent the further spread of the virus. It basically provided a simple alert system amid the pandemic. However, the NHS COVID-19 app was not free from issues.

In December 2021, the app sent around 700,000 alerts, prompting many to complain about a possible problem with its algorithm. In addition, there was also no means to determine if users were indeed self-isolating since everyone on the app remained anonymous.

But researchers revealed in a study published in February that the app helped prevent around one million COVID-19 cases and an estimated 44,000 hospitalizations and 10,000 deaths during its first year of use.

"The NHS COVID-19 app experienced high user engagement, identified infectious contacts well, and helped to avert appreciable numbers of cases, hospitalizations and deaths," the research team wrote.

"We conclude that digital contact tracing - a relatively low cost and rapidly available intervention - is a valuable public health measure for reducing transmission in any future epidemic waves of SARS-CoV-2 or other applicable pathogens."

The demise of the app was to be expected, especially after all COVID-19-related restrictions got lifted. Despite this, the app will have "a positive legacy" for future public health crises, Tony Blair Institute for Global Change chief policy strategist Benedict Macon-Cooney told the BBC.