SINGAPORE - About one million people here have downloaded Singapore's contact-tracing app TraceTogether so far, but National Development Minister Lawrence Wong said more need to come on board for the tool to be truly effective.

"In order for TraceTogether to be effective, we need something like three-quarters - if not everyone - of the population to have it. Then we can really use that as an effective contact-tracing tool," said Mr Wong in an interview with The Straits Times on Wednesday (April 1).

At the moment, though the one million downloads are a record for a Government app, they translate to about one in six people here having the app. It is also not sufficient to just download the app - people also need to turn on their Bluetooth function to ensure the app is running, Mr Wong added.

The app leverages short-distance Bluetooth signals between phones to detect other participating TraceTogether users in close proximity.

Mr Wong explained that the app is useful because relying on a person's memory during contact tracing takes time and can lead to lapses. The app will be a better way to "track down all that the person has been to, and the close contacts, then the ability to catch all of the close contacts would be much more comprehensive and faster", he said.

"If we had the app, if once that infected person was identified through the app, you would know who are the close contacts and immediate action could have been taken right away," Mr Wong said.

Launched on March 20, the app is able to identify people who have been in close proximity - within 2m for at least 30 minutes - to coronavirus patients using wireless Bluetooth technology, and is especially useful in cases where the infected persons do not personally know everyone whom they had been in close proximity with for an extended duration.

On its website, TraceTogether developers said that keeping the app running all the time will not drain a phone's battery significantly.

The authorities have also stressed that the app collects only the data it needs.The only data that is collected by the Government through this app is the user's mobile number, which is logged so that the Health Ministry can contact users quickly if they were in close proximity with an infected case.

The app also does not collect or use users' location data, but only records who they might have been close to.

Related Story Tough decisions painful but necessary to save lives, says Lawrence Wong

Related Story Coronavirus explainers: What you should know to protect yourself