NEARLY one in five confirmed Covid cases in Scotland in the past week were reinfections. 

Official figures from Public Health Scotland show that 21,914 people tested positive in the week to July 3, up 42.5 per cent on the previous week. 

Of these cases, 4,001 (18.3%) were detected in people who had previously tested positive for Covid more than 90 days ago. 

PHS cautions that the true number of infections will be much higher since routine PCR testing is no longer available and most people now have to purchase lateral flow kits. 

HeraldScotland:

Estimates based on surveillance by the Office for National Statistics suggest that one in 18 people in Scotland had Covid by the week ending June 24, the highest virus rate in the UK.

Updated hospital data also shows that there were 1,538 people in hospital with Covid as of July 3 - up by 18% from 1,298 the previous week, and from 590 at the end of May.

HeraldScotland: Hospital occupancy for patients with Covid is increasingHospital occupancy for patients with Covid is increasing

At the BA.2 peak in April, there were 2,406 patients in hospital with Covid. 

As all hospital patients continue to be screened for Covid on and during admission, this remains an accurate guage for the prevalence of the virus in the community.

It comes as a new analysis by PHS, published on Tuesday, said that the existing indicators used to evaluate Covid's impact on the NHS are "no longer optimal for describing the severity and impact of Covid-19 in Scotland" and should be reviewed.

READ MORE: Why Covid reinfections could be a much bigger problem than expected

Between January to April this year, only 43% of deaths which occurred following a positive Covid test were considered to have been caused by the virus, compared to 94% during the first wave of the pandemic. 

By the end of April, it found that approximately 30% of the Covid positive patients in hospital were there "because of" the infection. 

However, infection control protocols mean that all Covid patients, regardless of symptoms, have to be isolated. 

As a result, PHS stressed that all Covid admissions "contribute significantly to hospital pressures". 

Reinfections have become more common since Omicron became dominant in December. 

This is partly due to mutations which make it more "stealthy" and less likely to be remembered by the immune system. 

Research by Imperial College London found that UK healthcare workers who had been triple-vaccinated but never infected and then caught Omicron actually mounted a stronger immune defence against previous Covid variants such as Delta and Alpha than they did against Omicron, leaving them exposed to repeat infections as new forms spring up.

READ MORE: BA.4 and BA.5 Omicron causing 80 per cent of new cases

As a result, new Omicron waves - caused by BA.2 and now BA.4/5 - have been able to occur just two to three months apart. 

Danny Altmann, a professor of immunology at Imperial, described Omicron as an “especially stealthy immune evader”, adding: “Not only can it break through vaccine defences, it looks to leave very few of the hallmarks we’d expect on the immune system – it’s more stealthy than previous variants and flies under the radar, so the immune system is unable to remember it.”