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What we know about the Delta strain and how it's spreading in Ireland

It’s not all bad news: one dose of a two-dose vaccine still gives strong protection against hospitalisations from Delta.

Image: AAP/PA Images

THE DELTA VARIANT of the coronavirus SARS-CoV-2 now accounts for 20% of all of last week’s case numbers – but things aren’t as scary as they first appear.

The B1.617.2 variant, first identified in India in December 2020, has now spread to 60 countries and has caused Covid-19 outbreaks in England, Lisbon in Portugal, Moscow in Russia and in Sydney, Australia.

NPHET is due to advise the Government next Thursday on the epidemiological situation in Ireland, ahead of the next phase of reopening due on Monday 5 July.

Why is the Delta variant so concerning?

In short, because it is so much more transmissible and also possibly more dangerous.

Several lab tests have also shown that the Delta variant seems to have a slightly stronger resistance to vaccines than other variants do.

Dr Kim Roberts Assistant Professor in virology at Trinity College Dublin told RTÉ’s Morning Ireland that the Delta variant is “very nasty” and its several mutations make it more infections and easier to spread from one person to another.

How much more transmissible is it?

It’s estimated to be around 40-64% more transmissible than the Alpha (or British) variant, which was around 50% more transmissible than the original strain of SARS-CoV-2 – the virus that causes Covid-19.

Roberts said that there have been cases abroad where the variant spread after brief exposures of a few seconds with another person – but in many cases, the people involved were not wearing masks.

nsw-coronavirus-covid19 Cars line up for Covid-19 testing at Bondi in Sydney today. Source: AAP/PA Images

In Australia, a cluster is thought to have emerged after a person infected with the Delta variant had “fleeting” contact with other customers, and is concerning New South Wales authorities.

Security camera footage showed “they just passed each other in the store” – but it’s important to note that neither were wearing masks. The virus was also transmitted to a person who was sitting outside the café the infected person had visited.

“We also need to recognise that this Delta variant… is actually a gold medallist when it comes to jumping from one person to another,” New South Wales state Premier Gladys Berejiklian told reporters in Sydney.

How are symptoms different?

There is some suggestion that the symptoms of the Delta variant are slightly different – though it isn’t clear if this is linked to the younger ages of the population that it infects.

The global ZOE Covid Symptom study, which has tracked Covid-19 symptoms since May, has found that the main symptoms of Covid-19 in the UK have changed to a headache, a sore throat, runny nose, and a fever, in that order of frequency.

A loss of taste and smell, and a cough are much less common with Delta than had been with previous variants.

shutterstock_1283704306 Source: Shutterstock/fizkes

Is it more dangerous?

This is also unclear, but there is some suggestion that the variant is more dangerous if contracted – the Delta variant is associated with more severe Covid disease than previous variants, according to one study.

The spread of the Delta variant is leading to increased hospitalisations in the United Kingdom, but at a lower level than would have been expected due to vaccination.

A study by Public Health England showed that there were 73 deaths among people who had contracted the Delta coronavirus strain, from 1 February to 14 June.

Of that 73, 47% were unvaccinated, 14% were more than 21 days after their first dose, and 36% were more than 14 days after their second dose.

Vaccines vs Delta: the bad news 

A British study published in the Lancet medical journal in early June looked at levels of neutralising antibodies produced in vaccinated people exposed to the Delta, Alpha (first identified in Britain) and Beta (first identified in South Africa) variants.

It found that antibody levels in people with two doses of the Pfizer-BioNTech shot were six times lower in the presence of the Delta variant than in the presence of the original Covid-19 strain on which the vaccine was based.

The Alpha and Beta variants also provoked lower responses, with 2.6 times fewer antibodies for Alpha and 4.9 times fewer for Beta.

A French study from the Pasteur Institute concluded that neutralising antibodies produced by vaccination with the Pfizer-BioNTech jab are three to six times less effective against the Delta variant than against the Alpha variant.

Vaccines vs Delta: the good news

The studies on vaccine efficacy in a lab setting is a bit different to those in the real world. 

In particular, these types of scientific studies do not take into account a second immune response in the form of killer T-cells – which attack already-infected cells and not the virus itself.

As a result, real-world observations are crucial to measuring vaccine effectiveness – and the first results are reassuring.

According to data published last week by Public Health England, vaccination with Pfizer-BioNTech and AstraZeneca is almost as effective at preventing hospitalisation in the case of the Delta variant as it is in the case of the Alpha variant.

Two doses of the Pfizer-BioNTech jab prevent 96% of hospitalisations due to the Delta variant, while AstraZeneca prevents 92%, according to a study involving 14,000 people.

And this is the main aim of what we want vaccines to do: to prevent serious illness, hospitalisation, and death from Covid-19.

If the vaccines also stop the transmission of SARS-CoV-2, then that’s just a nice bonus.

The vaccines are still quite effective at preventing transmission of Covid-19, however: the Pfizer vaccine’s efficacy is between 79% and 88% against infection from the Delta strain of Covid, while AstraZeneca’s is between 60% and 67%, both after two doses.

One-doses give strong protection against Delta hospitalisations

But lab and real-world tests both conclude that one dose of any vaccine only gives limited protection against the Delta variant.

Studies suggest that a single dose of Pfizer will drop your protection from the Delta variant from about 50% to about 36%.

Both Pfizer and AstraZeneca offer significantly less protection against infection after just one dose (AstraZeneca: 30%, Pfizer: 36%), but still offer good protection against hospitalisations (AstraZeneca: 71%, Pfizer: 94%).

Not enough data exists yet to determine the Janssen vaccine’s effectiveness against the Delta variant, and Moderna’s efficacy is estimated to be the same as Pfizer’s.

How did it take such a strong hold in the UK, and how long before it takes hold in Ireland?

The UK is one of the best countries in the world for sequencing variants of coronavirus – this is the process of not simply testing for SARS-CoV-2, but testing what strain of the virus it is.

Because of this, the UK was very fast at identifying the Delta strain in the UK, and tracking its spread in the UK – meaning the UK was aware very early on how many cases of the Delta strain they had compared to other countries.

It can take roughly two weeks for a sample of the coronavirus to be sequenced in Ireland to determine what variant it is.

It’s also the case that the UK Government has been accused of being too slow to put travel quarantine restrictions in place for countries where the Delta variant was surging in the Spring.

Similarly, the Irish Government had resisted putting travellers from the UK on its mandatory hotel quarantine list – though it did increase the number of restrictions on those travelling to Ireland from Great Britain last week

How exactly are Delta cases spreading in Ireland?

The two places on the island of Ireland where suspected Delta outbreaks are thought to have fuelled a Covid surge are Athlone and Derry.

At last week’s NPHET briefing, Dr Holohan warned people that the Delta variant makes up over 20% of new cases in Northern Ireland, and that people should be mindful of that if they are thinking of travelling to the North.

“We can already see that there is a significant change in the spread of infection in some parts of Northern Ireland, including in the region of Derry,” he said, “where the seven-day incidence is in the region of about 130 per 100,000.

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“On the island of Ireland, that would be one of the highest incidences we’re experiencing.

“And so, no more than anywhere else within the country, people should take all those things into account.”

In Athlone, where a gathering took place on the west side of the River Shannon on 11 June linked to the local community.

14 primary cases have been identified as associated with that gathering, but have not yet been officially confirmed by whole genome sequencing.

The HSE is appealing for people who were socialising by the river Shannon in Athlone on 11 June to attend Covid-19 test centres, saying that identified cases are “probably” the Delta variant.

Dr Una Fallon, director of public health at HSE Midlands, told RTÉ Radio that it is difficult to investigate this gathering as it didn’t take place in a setting where contacts can be easily traced, such as a workplace or a school. 

Cases would’t have spread due to outdoor transmission alone, as people would have travelled to and from locations together, and some attended house parties that evening.

Up until last week, Ireland was doing well at keeping the Delta variant at bay, which NPHET members said was due to the travel restrictions and work of public health teams in enforcing them. Over 80% of the Delta variant cases reported in Ireland have been located in Dublin, CMO Dr Tony Holohan said last week.

Will the surge impact re-opening?

There are no plans to delay the 5 July easing of restrictions, which includes the reopening of indoor dining, sources have told The Journal.

It had been suggested that the sudden increase in the proportion of Delta variant cases in the daily confirmed cases may derail reopening plans as they have in the UK.

In England, the spread of the Delta variant delayed the lifting of the final set of restrictions on 21 June by four weeks. Social distancing restrictions were to be lifted and nightclubs had been due to reopen for the first time in over a year.

Similar delays were announced in Northern Ireland and in Scotland. 

Northern Ireland’s Department of Health have estimated that there could be 1,000 cases a day by the end of the summer, if the Delta variant becoming dominant in the region; 85% of the adult population having received two doses of vaccine; and the public continuing to adhere to social distancing and hygiene guidance.

Despite the concern, discussions around the Delta variant at Cabinet today have been described as “calm” – as authorities are more concerned at a rise in hospitalisations or ICU numbers, rather than daily case numbers.

With reporting from Nicky Ryan and AFP.

 

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