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'Antigen tests are just not as good as PCR': The five main points from today's NPHET briefing

‘Don’t travel unless you’re vaccinated’, why there hasn’t been a Delta surge here yet, and ‘buffer, not butter’ were discussed by NPHET members today.

Image: Leah Farrell

PUBLIC HEALTH OFFICIALS today reported a further 373 new cases of Covid-19 in Ireland, with 54 people with Covid in hospital, and 19 in ICU.

Although data relating to the number of deaths associated with Covid-19 have been affected by the cyber attack on the HSE’s IT systems, preliminary figures given at today’s briefing indicate that there have been 38 Covid-related deaths from 18 May-16 June.

There have been a total of 24 deaths notified in May so far.

Today’s briefing was lead by Chief Medical Officer Dr Tony Holohan, deputy Chief Medical Officer Dr Ronan Glynn, and chair of the NPHET Irish Epidemiological Modelling Advisory Group, Professor Philip Nolan.

1. Antigen tests: I can’t believe it’s not butter

Dr Tony Holohan was asked about an Oireachtas committee appearance yesterday, and a particular demonstration given by a member of NPHET on antigen testing.

Consultant immunologist Professor Mary Keogan gave a demonstration to show that if tonic water is mixed with the antigen test, it can produce a positive Covid result.

At this evening’s briefing, Holohan clarified two things:

  • During that demonstration, Keogan had produced a negative Covid antigen test using a buffer – not butter, as had been erroneously reported yesterday
  • The demonstration wasn’t suggesting that people would use the tests to fake a Covid positive test, but to show the volatility of the tests compared to PCR tests.

Holohan said that antigen tests should be used in outbreak settings, in high-risk environments, and have been used in these cases.

Holohan acknowledged that in the settings where antigen tests are suggested for use, they wouldn’t be self-administered, but said that there are broader concerns, particularly around their effectiveness in asymptomatic cases, which could be as low as 51%.

It’s just not as good as PCR… It’s not a skepticism of antigen testing, it’s the absence of evidence to show that they work well enough to recommend their use.

A pilot use of antigen tests for screening purposes is taking place at four universities this summer, after academics suggested they use these settings for trialing the real-world effectiveness of antigen testing. 

In response to using antigen testing to help the resumption of tourism and the aviation sector, Holohan said:

“‘Don’t travel unless you’re vaccinated’ I think will continue to be our message.

“If we can do that, and keep disease incidence low across Europe, we can see the safe resumption of airline travel without the need for any form of testing, which, frankly, would get in the way of the experience. It would be a strange experience to have us all having to subject ourselves to substantial testing as we move in and out of airports.”

2. NPHET’s one big worry

When asked whether the much-criticised gathering on South William Street in Dublin City a number of weekends ago had resulted in more cases of Covid-19, Dr Holohan said that there have been a number of outbreaks related to “all sorts of activities”. 

We have much less concern to express about that than we would have for people being able to mingle and come into close contact… We are seeing a persistent high rate of transmission among the 19-20 age group – that comes as a result of contact among people who are still not vaccinated, and we have to express a continuing concern about that.

“If we had one key concern about how this could all go wrong – the confluence of a number of different things that could all occur in the coming weeks.

It will be a fact that we have still a proportion of the population that are unvaccinated, the potential or opportunities for people to go travel, and if people engage in travel before they are vaccinated, mix with other people in other countries who are not vaccinated, the potential for variants of concern to be transmitted, and then those people come back here unvaccinated, and indoor hospitality is open, our third level is open in the autumn, the confluence of those things could lead to a significant change in transmission. 

3. Travel to Great Britain and Northern Ireland

Dr Holohan advised the public against non-essential travel to Great Britain amid concerns over the Delta variant.

Advice on travel to Northern Ireland from the Republic has not been formally made, but Holohan said they are “concerned” about the situation across the border.

He said this evening: “We’re strongly advising against non-essential travel between here and the UK, because of the concerns in terms of transmission of the Delta variant.”

Asked if the advice applied to Northern Ireland, he said: “The seven-day incidence that we’ve seen across Northern Ireland, and particularly Derry, in recent days, we know it will be of concern to our colleagues in Northern Ireland and it is of concern to us.

We are expressing our concern about that. We haven’t formally advised on that at this moment in time. We’re keeping a very close eye on that.

4. Why isn’t the Delta variant an issue here the way it is in the UK?

In short, there hasn’t been a huge surge of the Delta variant here because we’ve been able to catch it so far in those who have tested positive after travelling from the UK.

There have been 188 cases of the Delta variant confirmed in Ireland – on Wednesday evening Cabinet was told there were 139 cases. Dr Holohan said that “well in excess of 80%” of the Delta variant cases reported in Ireland have been in Dublin.

Professor Nolan said that there hasn’t yet been a Delta surge here “largely because the majority of these cases have been intercepted at, or soon after the point of entry”.

So, in the UK, there are very significant levels of community transmission and community spread, and therefore, normal exponential growth.

Frankly, it is a testament to the work of our public health colleagues that the variant hasn’t been allowed to escape into the country.

Holohan said that they have not recommended that mandatory hotel quarantine be introduced for the UK.

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5. Low number of deaths and hospitalisations

And finally, in some good news, Dr Holohan said this evening: “We are now experiencing near elimination of Covid-19 in the vaccinated population.”

Expanding on that point, Professor Philip Nolan said that there are “very few cases”, or, on most days “no cases” in those aged 65 and older. He said that the number of cases 

In relation to hospitalisations, Nolan said: “The number of people in hospital and the number of admissions to hospital is declining quite quickly.”

“And if you look at the slope at the end of that red curve there, the number of people in intensive care, the number of people requiring mechanical ventilation, and you can barely see the admissions bars, because we’re looking at typically 2 admissions every 5 days – so less than one admission per day.”

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