The risk of being infected with Delta and Omicron at the same time

The spread of the Omicron and Delta variants could trigger two separate epidemics during which some people could be hit by simultaneous infection with both strains, research suggests.

Experts from the Scientific Advisory Group for Emergencies (Sage) have discussed both Delta and Omicron spreading “concurrently”, predicting that the latter could “partially or largely replace Delta” within weeks. “But the extent of this depends on the degree to which they are infecting different cohorts of people, which is not currently known,” according to the i news site.

Minutes from a Sage meeting on Tuesday reportedly suggest that “both could continue to spread concurrently”. And this prediction has raised fears that some people could become infected with both variants at the same time, largely because Omicron appears to have a higher reinfection risk.

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Can you be reinfected with Omicron after Delta?

The short answer appears to be: yes.

The evidence we have so far suggests you can catch Omicron even if you’ve been infected with another variant of Covid, such as Delta or Alpha.

Cari van Schalkwyk and Juliet Pulliam, from the South African Centre for Epidemiological Modelling & Analysis (Sacema), and Harry Moultrie, from the National Institute for Communicable Diseases in Johannesburg, said that their research found Omicron was “associated with increased ability to evade immunity from prior infection”.

In an article on The Conversation, the trio explained that “a reinfection is defined as a positive SARS-COV-2 test more than three months after a previous positive test.

”We found that the relative risk of reinfection was much higher (at least 3-fold) with the Omicron variant than it was with the Beta and Delta variants,” they added.

Can you have both at the same time?

The evidence suggests that despite the previous infection, people can still catch the Omicron variant, which in turn means that there is “plenty of scope for the variants to exist side by side”, according to the i news site.

This is also compounded by the fact that Omicron appears to evade vaccines more successfully, meaning it can sweep through those who have had one or two jabs, while the Delta variant continues to infect the unvaccinated.

“We may have two simultaneous epidemics, one from Omicron and one from Delta,” said Professor Paul Hunter, from the University of East Anglia.

“This raises the concern about Delta and Omicron co-infections, where both variants infect the same person at the same time. In general co-infections of any respiratory viruses are associated with more severe disease and we certainly saw that early in the pandemic with Covid and influenza co-infections.”

Dr Paul Burton, Moderna’s chief medical officer, also told MPs on the Science and Technology Committee that data published in South Africa showed that it was possible for people to “harbour both viruses”, reported the Daily Mail.

“There’s certainly data, there have been some papers published again from South Africa earlier from the pandemic when people – and certainly immunocompromised people – can harbour both viruses,” he warned. “That would be possible here, particularly given the number of infections that we were seeing.”

Burton also told the committee that the high number of infections in the UK increases the risk of “recombination events”, where strains of virus “swap” DNA, possibly triggering the creation of a new, more dangerous variant.

Most places have dominant variants of the virus, so becoming infected with two strains of Covid-19 remains “unlikely”, said the Daily Mail.

But “huge, poorly controlled outbreaks”, like the ones in the UK and US over the winter, can “significantly raise the risk of the combination events simply because the number of infections is higher”, the paper added.

The “exponential growth” of the Omicron variant means that we could find cases of people being infected with both variants in a “couple of weeks”, said Donato Mancini, the Financial Times’ pharmaceuticals correspondent, during a Twitter broadcast.

But the high levels of vaccine coverage in the UK should “help hedge against severe disease”, he added.