Covid-19: Danish agency says infection can occur twice with Omicron variant

Two sub-variants of the Omicron variant of Covid-19  – known as BA.1 and BA.2 – are widespread in Denmark. Infection with one can occur in an individual with a previous history of infection with the other, researchers have found.

A file photo showing Danish Covid-19 test result history
A file photo showing Danish Covid-19 test result history on someone's phone. Photo: Bo Amstrup/Ritzau Scanpix

According to a report published by national infectious disease agency State Serum Institute (SSI) on Monday, infection with one subvariant of the Omicron variant of Covid-19 does not give full immunity against reinfection, since a different subvariant can escape immunity.

Around 2 million people in Denmark have tested positive for Covid-19 – almost a third of the population – since Omicron emerged in the country in November 2021, according to SSI.

The BA.1 subtype of Omicron is the most prevalent but another variant, BA.2, is gaining ground in many places worldwide, the agency writes.

“This pattern is reflected very clearly in Denmark. The majority of those infected with Omicron in December were affected by BA.1. However, in January, BA.2 gradually became ever more prevalent. This variant currently accounts for most coronavirus infections in Denmark, whereas BA.1 is now seen much more rarely,” SSI writes.

Gene sequencing of positive PCR tests by SSI detected “67 cases in which the same individual had become infected twice at a 20-60-day interval and where both infections were due to Omicron subtypes”.

In 47 of the 67 cases, the first infection was with BA.1 and the second with BA.2.

The majority of the reinfected individuals were “young and unvaccinated” according to SSI.

“Most experienced mild symptoms during their infections. The difference between the severity during their first and second infection was negligible. None of the infected individuals had become seriously ill, and none required admission to hospital,” the agency writes.

The SSI study shows that infection with two different Omicron subtypes “is possible” but “seems to occur relatively rarely in Denmark”, the agency writes.

Reinfections “have mainly affected younger unvaccinated individuals”, it also notes.

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Covid-19: Infections trend downwards in all Danish regions

A total of 22,784 new cases of Covid-19 were detected in Denmark in the latest daily update, published on Friday.

Covid-19: Infections trend downwards in all Danish regions

The positive results were found among 90,012 PCR tests, giving a test positivity rate of 25 percent. The proportion of test results has been around 25-30 percent in recent weeks, although the number of tests administered has gradually decreased since Denmark lifted Covid-19 restrictions on February 1st.

The data comes from the national infectious disease agency State Serum Institute (SSI).

Danish hospitals now have a total of 1,762 patients with Covid-19. But a large proportion of these were admitted for reasons other than Covid-19 while incidentally having tested positive for the coronavirus.

Of the 1,762 patients, 45 are admitted to ICU wards and 17 are receiving breathing assistance from a ventilator.

It is 16 days since the highest number of new cases was recorded in Denmark, with 55,120 registered on February 9th.

The last week has seen the number of confirmed cases falling in 97 of Denmark’s 98 municipalities, with the only exception being the island of Samsø. That suggests that western and rural parts of Denmark have now reached the peak of the Omicron wave of infections, following on from the earlier peak in Copenhagen.

Experts in Denmark have long predicted that infections would decrease while stating that the stable number of ICU patients was evidence that the pandemic was not in a critical situation despite high infection numbers.

An additional 40 deaths with Covid-19 were registered on Friday. SSI on Thursday issued a report in which it estimated that around half of recorded deaths with the virus are due to reasons other than Covid-19.

A person is included in data for Covid-19 related deaths in Denmark if they have returned a positive PCR test 30 days or less prior to their death.

READ ALSO: EXPLAINED: Are deaths from Covid-19 in Denmark increasing?