The NHS Covid-19 app has been downloaded more than 10 million times since its launch last week.
Some six million people downloaded the contact-tracing app on the first day it was launched, the Department of Health and Social Care said.
The app was launched for people in England and Wales on 24 September.
Health secretary Matt Hancock said: “The enthusiastic response of over 10m people downloading the app in just three days has been absolutely fantastic.
“This is a strong start but we want even more people and businesses getting behind the app because the more of us who download it the more effective it will be.
“If you haven’t downloaded it yet I recommend you join the growing numbers who have, to protect yourself and your loved ones.”
The app uses Bluetooth technology to track time and distance between devices. It also offers a QR code check-in capability at bars, restaurants and other venues, designed to aid NHS Test and Trace in contacting customers with public health advice should there be a Covid-19 outbreak.
More than 1.5 million venue check-ins were recorded on Saturday, 26 September, while more than 460,000 businesses have downloaded NHS Test and Trace QR code posters.
Dido Harding, executive chair of NHS Test and Trace, said: “The integration of contact tracing and venue check-in is a key feature of the NHS Covid-19 app, giving us a easy and straightforward way for us all to help protect one another.
“I urge any businesses yet to print and display the posts to join this effort and download them now.”
NHS Test and Trace has not said how many downloads would constitute success, but highlighted Oxford University research that found a “well-staffed manual contact-tracing workforce combined with 15% uptake of an exposure notification system could reduce infections by 15%”
Despite the positive reception to the app it was launched with issues reporting test results.
Users were unable to record a positive test result if they had booked a test elsewhere and not through the app.
The Department of Health and Social Care (DHSC) said everyone who receives a positive test result can now log their result on the app.
“If you get a test in a NHS hospital, through a PHE lab – which carry out tests for NHS hospitals – or in a surveillance study, you can request a code from NHS Test and Trace to log a positive result,” it said in a statement.
Test results taken as a result of Office for National Statistics surveys, and those processed by an NHS hospital or Public Health England lab were initially not able to be shared via the app.
A DHSC spokesperson confirmed further developments to the app are underway to allow negative test results to be entered.
Currently a user will only receive a code if they tested positive for the virus. Those who enter their symptoms without entering a test result trigger the self-isolation countdown timer.
The isolation countdown timer was designed to remind people to quarantine if they are thought to have Covid-19.