The administrative error was identified on Wednesday, after letters had gone out to the individuals informing them that they had coronavirus.
The letter they should have received was the one telling them that they had been identified as a contact of a confirmed case.
Correct letters have now been sent out, and each of the individuals have been contacted by telephone to explain the mistake and apologise for the upset it may have caused.
A spokesperson for Public Health said the letters must have been a big shock for the people involved.
‘Since the beginning of the pandemic, one of Public Health’s many roles has been to support and advise people who have tested positive for Covid-19.
‘The team know from their first-hand experience how distressing such news can be and apologise sincerely to all of those who have been wrongly given such information today as a result of this mistake.
‘To be clear, no one will receive a letter confirming they have tested positive for Covid-19 and are subject to mandatory quarantine without having first received a telephone call from a Public Health Services clinician.’
Yesterday there remained three known active cases of coronavirus in the island, and those people have been told they must self-isolate.
Guernsey’s borders strategy is currently based on three groupings of countries and regions.
People arriving from Group A destinations, which includes London, have to quarantine for 14 days.
Travellers from Group B places, including Jersey and the south of England, can take a test after seven days of quarantine and if they are negative they are free to be released out, unless they have sat close to a positive case.
Only visitors from the Isle of Man are not subject to any restrictions.
The island’s authorities are working towards phase 5c, which will replace much of the quarantine periods.
However, the authorities are also keeping a watchful eye on the worrying situations in the UK and France, where there are fears that the rate of infections could grow exponentially.