Counterfeit vaccine passes have forced pharmacies in Germany to stop issuing the certifications.
The passes allow citizens more freedom, especially when it comes to travel.
Authorities in the country say hackers managed to spoof two passes using fake pharmacies on digital forms.
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The German Pharmacists’ Association said it found no signs of other counterfeiting after a tip off from the Handelsblatt newspaper.
Vaccine centres can also approve the accreditation.
It comes as the Italian government announced that proof of coronavirus vaccination or immunity will be needed from next month to access services like gyms, pools, sports stadiums, casinos and museums.
The restrictions start from 6 August, as the country battles a fresh surge in COVID cases.
France introduced similar requirements from Wednesday this week, with negative tests also being a way to prove validity for entry.
Restaurants and cafes are also included in the restrictions.
Many parts of the EU are using the bloc’s certification process to allow more parts of society to open up, separate from requiring proof of status on arrival.
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And It was announced earlier this week that proof of vaccination will be required at “crowded” venues in the UK from September.
In Greece indoor hospitality venues, as well as nightclubs, music venues and indoor cinemas, require proof of immunity.
Spanish regions have individual rules, but some areas – like Barcelona – require proof of vaccination, a negative test or proof of antibodies before attending events of more than 500 people.
In low risk parts of Portugal, proof of status is needed for those looking to check in to hotels.
Other areas with higher rates require vaccination, antibodies or a negative test for activities like eating indoors.
In the Netherlands, requiring a digital COVID certificate allows venues to operate at a higher capacity.
Nations are working to try and encourage vaccination uptake, especially among younger groups.
While many parts of the continent struggled to get their efforts up and running at the start of the year, most are now seeing good inoculation rates.
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Around 60% of Germans have had one shot and 47% are fully vaccinated,
Some 48.2% of Italian have had two vaccine shots, while 14.1% are waiting for a second dose.