The app will not show Covid test results but it is hoped that they will be incorporated by the time domestic Covid status certification is due to be introduced for mass events on June 21.
Those without smartphones were told to call 119 to order a letter confirming their vaccination status.
The app, developed by NHS Digital and NHS England, was originally created to allow people to book appointments, repeat prescriptions and see their full medical records.
The Government is urging people to check the entry requirements for their destination country well in advance of travelling.
'You can access the app through mobile devices such as a smartphone or by tablet.
The government website says: "From May 17, you may be able to show your Covid-19 vaccination status as proof of your status when travelling overseas to some countries or territories. We recommend you register with the app before booking worldwide travel".
No. There are not many countries that now accept proof of vaccination and most people will still need to follow other rules when travelling overseas such as getting a negative pre-departure test.
"You can access your Covid-19 vaccination status through the free NHS App from May 17". Proof of your Covid-19 vaccination status will be shown within the NHS App. "A full course is now two doses of any approved vaccine". This must be at least five days after you've completed your course of the vaccine. The letter will take up to five days to reach you.
A post on the Newbury Vaccination Centre Facebook page confirmed the news and appealed to residents to use the app and not contact their GP's surgery to try to gain evidence of a vaccine.
Children can not get vaccination status. Any children you are travelling with may need to show proof of a negative Covid test.