Almost 35,000 people who tested positive for Covid in Scotland have had the virus before, according to the latest figures, which also show intensive care admissions have risen by 21%.
Public Health Scotland (PHS) data has shown for the first time how many people are contracting the virus again after a previous infection.
Scientists say it is important to include re-infections in order to understand the dynamics of the spread of immune-evasive variants that emerge, while it also sheds light on why some individuals may get infected over and over.
As of January 24, 3.1% of positive PCR test results (34,774 out of 1,158,822 total cases) were determined to be re-infections but the rate climbed to almost 10% earlier in the month.
The highest numbers have been reported amongst people aged 20 to 24, with more females affected “likely due to higher rates of routine occupational screening by women in healthcare roles”.
The overall rate of re-infections in Scotland remained low at 0.6% until the emergence of the more transmissable Omicron variant, when re-infection rates climbed to 6.4% in December 2021 and 9.8% in January 2022.
Repeat infections have been highest in Greater Glasgow and Lanarkshire and Scotland’s rate is broadly in line with England where 4% of cases were recorded as re-infections as of January 31.
Possible re-infections were first reported by Hong Kong in August 2020. Scientists say a key issue in identifying cases is distinguishing between viral persistence and true re-infection.
In Scotland, they are defined as a positive result 90 days or more after a previous test.
Professor Rowland Kao, an epidemiologist at the University of Edinburgh said repeat infections are likely to be due to exposure risk and “inherent likelihood of becoming infected, once exposed.”
He said: “The additional data on reinfections will be useful information, particularly at this time, when it is likely that re-infections will be occurring with increasing frequency and therefore the rate of new infections occurring decreasingly representative of the true course of the epidemic.
“If there are high numbers of reinfections then this will be due to a combination of the sheer number of people already infected, and the fact that, as immunity wanes, the likelihood is that protection is also waning.
“Thus having an estimate of the rate of re-infection (and remember it is only an estimate as many people will not know they previously had covid) will help to determine how quickly immunity is waning across the country and therefore crucially, when further boosters may need to be considered.
“We need to know these things in order to better target interventions of various sorts – how important, for example, particularly workplaces are likely to be, and how some individuals are therefore going to be exposed to more risk.”
Nicola Sturgeon said yesterday in her update to parliament that she is confident Scotland is “entering a calmer phase of the pandemic” but has warned “case levels are likely to remain high for some time.
The First Minister said 26 cases of a new sub-variant of Omicron, known as BA.2, have been identified.
She said there was no evidence at this stage to suggest that BA.2 causes more severe disease than the Omicron variant but said it does appear to have the ability to “out-run” it which may indicate that it is more transmissible.
While hospital admissions with a laboratory confirmed test of Covid-19 have continued to decrease, today’s PHS report shows there has been an increase of 21.7% in intensive care admissions.
In the week ending January 30, there were 28 new admissions to ICUs with a laboratory confirmed test.
As of January 25 January, there were 704 admissions to hospital with a positive test, a decrease of 18% from the previous week. The highest number of new admissions are now in those aged over 80 while 50% are among those aged 60 and over.
Hospital admissions continue to be 3-4 times lower in individuals who have received a booster or third dose of a vaccine, than in unvaccinated individuals.
The figures also show that 71.3% of those in the least deprived areas have received either their third dose or booster vaccination, compared with 51.0% in the most deprived areas.
Uptake amongst pregnant women has been consistently lower among black, Caribbean, or African ethnicity compared to white, South Asian or mixed ethnicity