Government guidance has insisted that anyone who is fully vaccinated and has come into contact with someone who has tested positive for coronavirus is strongly advised to immediately take a rapid lateral flow device (LFD) test every day for 7 days or until 10 days since their last contact with the person.
Since the emergence of the new Omicron variant, government guidance has ramped up testing capacity offering home lateral flow test kits and making more PCR test sites available.
However, with fluctuating test availability and reports of initial lateral flow tests returning negative results followed by positive PCR test results, many are wondering when is the best time to test after being exposed to coronavirus.
Anyone who is not fully vaccinated and comes in contact with someone who tests positive must self-isolate for 7 days.
However, America’s national public health body the Centre for Disease Prevention and Control (CDC) states that individuals exposed to coronavirus should test five days after exposure or as soon as they begin experiencing symptoms.
Edinburgh University public health professor Linda Bauld, told The Independent that with the ready availability of home lateral flow tests, people should seek to get tested as soon as they find out they have been exposed to Covid-19.
“With this variant Omicron we can pick up quite rapidly,” Professor Bauld said.
“What happens is people are carrying more of the virus in their upper airways and it’s replicating quite quickly so even if they’re exposed to a small amount of virus we can pick it up very rapidly.
“If people have access to testing, as in they have it in their home already and they’re informed that they have come into contact with a positive case, it certainly is reasonable that within the first 24 hours to use one of those tests and to continue to do so for several days.”
Professor Bauld added, however, that in a circumstance where lateral flow tests were not readily available and they need to be rationed to the most vulnerable people and frontline staff, it may be best to wait at least two days before testing due to the decreased sensitivity of the home test kits.
“We’re very fortunate in the UK we have good access to regular testing but that is not the case in all countries, in the US and Canada they have to ration their testing” Professor Bauld said.
“The antigen tests which find a protein in the virus rather than the genetic material from the virus are less sensitive than the PCR test which means you may need a bit more virus built up in your body before a test has a positive result – you may have more of the virus replicating in your system if you give it a couple of days.”
Imperial University Public health expert, Professor Azeem Majeed agreed with government advice that people should begin testing immediately from when they are exposed and continue testing for 10 days after. He added that while many people become infectious from two days following exposure, it’s still safest to test daily from contact with a positive person, as the development of symptoms may vary between people.
In France, people who exposed to the virus are advised to get tested as soon as possible, while in Belgium, similar to the CDC, people who come into contact with someone who may be sick are advised to get a PCR test five days after the contact.
