90 days - don't understand

[123456LA]

So I'm confused. They tell you not to test again within 90 days of having covid because the PCR can pick up inactive viral fragments and show you as positive, yet they also say if you have new symptoms within these 90 days you must actually do a PCR test? But that to me makes no sense because your test may come back positive when it isn't actually positive? Am I being thick here?

It’s about probabilities. Most people won’t still be testing positive on a PCR after 90 days. Especially if they had a milder bout of Covid.

But until omicron, the chances of having a reinfection within 90days was so vanishingly small that if you did get a positive it was more likely you were one of the people who did still test positive than having a new covid infection.

With omicron that’s changed because even a recent delta infection doesn’t provide much protection from getting omicron. So with the huge levels of infection in the U.K. it’s far more likely that anyone with new symptoms has a new infection than they are one of the few still testing positive from an old infection weeks later.

@InCahootswithOrwell

It’s about probabilities. Most people won’t still be testing positive on a PCR after 90 days. Especially if they had a milder bout of Covid.

But until omicron, the chances of having a reinfection within 90days was so vanishingly small that if you did get a positive it was more likely you were one of the people who did still test positive than having a new covid infection.

With omicron that’s changed because even a recent delta infection doesn’t provide much protection from getting omicron. So with the huge levels of infection in the U.K. it’s far more likely that anyone with new symptoms has a new infection than they are one of the few still testing positive from an old infection weeks later.

...only the problem is that what OP says has been the official advice for months and months now AND long before omicron was even on the horizon. This is one of many mindless rules the govt forces upon us with not many questioning it.

it makes perfect sense!

If you have no symptoms then dont pcr as its likely old covid infection fragments

if you go from no symptoms to new symptoms+ postive pcr then balance of an accurate positive test chages so you isolate

it's not rocket science fgs its basic maths!

The problem really comes with being asked to do lateral flows (for work/school/before meeting up with others) and whether you should be doing these or not. I've done a few when requested despite having covid a month ago, and luckily seem to have returned to negative, but the govt advice very much suggested you shouldn't originally (unless you presented with new symptoms... Which I haven't.. but if I'm meeting up with friends who ask us all to test before getting in close proximity, also now govt advice, the two things then contradict).

@123456LA It's a really good question and one that I'd thought of too

@InCahootswithOrwell Great answer... All
these things are based on probabilities... Even a negative PCR has a non-negligible probability of being a false negative. I think many people struggle with that though and conclude that if a test can't give a 100% certain result, it's rubbish.

I think many people struggle with that though and conclude that if a test can't give a 100% certain result, it's rubbish

Which is weird in itself since most people happily accept less than 100% in other pretty important areas of life. There would be significantly less drivers on the road if everyone could only pass a test with100%!