Under the new testing method, samples are no longer taken by swabbing the back of a person’s throat. Instead, the person being tested spits in a cup. However, for the PCR test to work properly, this means the person being tested should not eat, drink, smoke, chew gum, rinse their mouth or brush their teeth half an hour before the test.

The European Centre for Disease Prevention and Control (ECDC) in May that saliva tests showed an overall similar sensitivity compared to nasopharyngeal swabs. “Saliva samples collection is easy, non-invasive, more acceptable for repeat testing and can be performed by non-healthcare professionals,” it said.

Evidence supports that saliva sampling can be used as an alternative for repeated screening of asymptomatic individuals, the ECDC said further. However, it added that “nasopharyngeal specimens remain the gold standards for covid-19 testing.”

Luxembourg at the end of June turned its large-scale testing scheme into an on-demand service. Previously, residents and cross-border workers could only get tested upon invitation as part of an effort to screen the population and weed out asymptomatic cases.

With the introduction of the CovidCheck--a testing and immunity certificate--testing became available on-demand to enable those who have not had the opportunity to get vaccinated to show a valid certificate for travel, events or venues using the system to admit larger crowds.

A private laboratory is at EU level saying the change in regime had caused it to lose business and created an unfair advantage for the provider of the large-scale testing scheme.