NSW’s hotel quarantine tell us a bit about asymptomatic Sars Cov2 – how prevalent is it? Initial data in NSW (where people were tested either if they were symptomatic, or on Day 10 of Hotel quarantine) showed that 40% of Sars Cov2 cases were completely asymptomatic. In more current data, where everyone is now tested on Day 2 of their quarantine, 88% of positive tests occurred in those with no symptoms (some would probably have gone on to develop symptoms after their positive test).

New South Wales publishes statistics every day of their testing of hotel quarantine. Currently every single person is tested (since 1 July, on Day 2 and Day 10 of quarantine), and in addition, anyone who develops symptoms is tested hen they develop. Before, that, NSW Health was testing everyone on Day 10, plus if they became symptomatic.  So all testing on Day 2 and Day 10 is testing of asymptomatic people. Astonishingly there are still quite a few people who test positive on Day 10 despite having had no symptoms to that point (and those in quarantine are asked about their symptoms daily). That means that they haven’t shown any symptoms since they arrived in Australia, and were isolated, and they have still tested positive to the coronavirus 10 days after they arrived. Since the beginning of the pandemic, asymptomatic transmission has been well known, and these statistics confirm that it is still a major part of the characteristics of this disease, even with serious monitoring of even minor symptoms by health professionals.

The graph shows that the proportion of people in Hotel Quarantine testing positive is quite material  – probably reflecting the prevalence of the virus in the world that we draw our returning citizens from. Even at Day 10 of Hotel Quarantine, without any symptoms, the most statistics shows 0.3% of people tested positive.

In the 156 days since this process started, 442 people have tested positive in Hotel Quarantine in NSW, out of 110,180 tests. 300 people tested positive on Day 2 without symptoms. Another 53 people tested positive after displaying symptoms (1.3% of those tested with symptoms, who would be a mixture of people arriving with symptoms, and people who tested negative at the beginning, and then developed symptoms). Then on Day 10, after no symptoms for all that time, another 89 people tested positive. So 88% of people tested positive before they had any symptoms, and 20% of all positive tests probably never developed symptoms (the day 10 positives).

Before 30 June, NSW Health was only testing people if they were symptomatic, or (after mid May) on Day 10 of their quarantine for all.  It is harder to find statistics about this earlier period, but the best I have found (on 30 June) have 109 cases identified after symptomatic testing, and 67 cases identified from asymptomatic testing on Day 10 of quarantine. Which suggests that around 40% of all Sars Cov2 cases get to Day 10 with no symptoms, consistent with other studies.

I’ve blogged before about asymptomatic coronavirus:

I’ve linked before to several pieces of research which try to work out how many asymptomatic carriers there are. There is more information about the Italian town of Vo in this study which I have just come across (from the filename it was published in the past few days):

On the first survey, which was conducted around the time the town lockdown started, we found a prevalence of infection of 2.6% (95% confidence interval (CI) 2.1- 3.3%). On the second survey, which was conducted at the end of the lockdown, we found a prevalence of 1.2% (95% CI 0.8-1.8%). Notably, 43.2% (95% CI 32.2-54.7%) of the confirmed SARSCoV-2 infections detected across the two surveys were asymptomatic….

And the statistics from NSW Hotel quarantine confirm the high prevalence of asymptomatic Sars Cov2, with 88% of all positive tests coming in asymptomatic people, and around 40% probably never developing symptoms.

As I’ve said before, the NSW Health team probably has the statistics for several really good pieces of research with all the excellent data they are gathering as part of this process (other states may too, but NSW Health seems to publish a lot more for people like me to look at). I hope that they do manage to get some research out – there is value to be added to the wider conversation.

Links

After my last post about vaccines, AstraZeneca has also announced preliminary results. They aren’t as good as the first two vaccines, and this Wired article analyses some other problems with what has been released so far.

THE MAKERS OF a third coronavirus vaccine announced positive results in clinical trials on Monday, setting off yet another round of excited news reports. This one, produced by a partnership between a University of Oxford research institute, its spinout company Vaccitech, and the pharmaceutical company AstraZeneca, does not need to be stored at freezing temperatures and would be cheaper and easier to produce than the high-efficacy vaccines produced by BioNTech-Pfizer and Moderna. Indeed, according to an initial write-up in The New York Times, Oxford-AstraZeneca’s is “expected to be relied upon heavily across the globe, to help curb a pandemic that has killed more than 1.3 million people.”

Sounds like great news, right? Monday’s press release from AstraZeneca presents “convincing evidence that [the vaccine] works,” said Science. But not everyone has been convinced. The price of AstraZeneca’s shares actually dropped on the news, and an analysis from an investment bank concluded, “We believe that this product will never be licensed in the US.” Over at STAT News, Anthony Fauci cautioned that we’ll need to see more data before coming to a conclusion. The skeptics have strong reasons to be concerned: This week’s “promising” results are nothing like the others that we’ve been hearing about in November—and the claims that have been drawn from them are based on very shaky science.

And the US has moved to debating how to start vaccinating people –  how should the vaccines be rolled out? Stat news has more.

Vaccines that prevent symptomatic Covid infection in roughly 95% of people vaccinated — as the data from clinical trials of the Pfizer-BioNTech and Moderna vaccines suggest — should, over time, help the country and the world return to a life where we can travel without quarantining; where sporting events can be played before live audiences, not cardboard cutouts; and where snowstorms are the only reasons school gets canceled.

But if we’re not careful, we could fail to take full advantage of the opportunity scientists and governments, pharmaceutical companies and philanthropic foundations have created for us.

And there’s a possibility that the pandemic off-ramp doesn’t merge with a straight road back to Normalville, but instead becomes a meandering country lane with the occasional detour. We may need to choose the right turns and avoid the potholes as we make our way to our destination. It will require patience.

Do read the whole thing, it discusses vaccine hesitancy, the ethical problems of testing new vaccines now that we have effective vaccines available, and how likely it is that the vaccines stop infection as well as symptoms.

The Australian Vaccination strategy is here,  and once again, reading it compared with the article about the US makes me glad to be in a country with a well functioning public service. So many of the questions in the article have already been answered. In particular, we’ve identified priority groups:

When vaccines are available, supplies will initially be limited and directed towards priority groups for vaccination. Deciding upon which groups to prioritise is difficult and contentious. Different candidate vaccines will vary in their efficacy to prevent or modify clinical endpoint outcomes, their safety profile, and their suitability for different age groups or people with underlying medical conditions.

The three priority groups identified by ATAGI are:

  • Those who are at increased risk of exposure and hence being infected with and transmitting SARS-CoV-2 to others at risk of severe disease or are in a setting with high transmission potential. This includes health and aged care workers; other care workers, including disability support workers; and people in other settings where the risk of virus transmission is increased, which may include quarantine workers.

  • Those who have an increased risk, relative to others, of developing severe disease or outcomes from COVID-19 including Aboriginal and Torres Strait Islander people, older people and people with underlying select medical conditions.

  • Those working in services critical to societal functioning including select essential services personnel and other key occupations required for societal functioning.

And one last fun link – a data analysis of Amazon reviews of scented candles, showing the correlation of one star reviews with the pandemic.

Life Glimpses

I spent time in an office this week – the first time since the 17th of March. It was… strange. The streets around felt completely normal to me, but in reality I imagine most companies in the office blocks in the CBD are still at a maximum of 50% occupancy, which probably means I’m not really used to a crowded street any more. It was nice to feel a bit of normality, even if the office I was in was probably at more like 25% occupancy. According to Citymapper, we are back to 48% of normal movements in Sydney.

My choir is now meeting in person! (outdoors) now that the NSW Department of Health allows up to 30 people to sing outside. We have found a lovely spot in the local area which was quite spectacular in this week’s thunderstorms. Next week NSW is relaxing the rules even further.

I had been hoping that this next post would be celebrating 28 days of no new local cases in NSW. Sadly, that’s not the case as we had a new one today, probably transmitted by hotel quarantine. Regardless, for all of my readers in places with few to no local cases – please get yourself tested for the slightest of symptoms. The Adelaide outbreak was stopped quickly because it was found quickly. Even though the chances of your sore throat being Covid19 are small, they are still not zero, even in Tasmania, the Northern Territory or the ACT (where it has been more than 100 days since the last local case).

Bit of Beauty

For anyone who has spent time on an Australian beach and been stung, this picture of a beach covered in bluebottles is hard to look at. But take a step back and forget the pain you have experienced from these little creatures, and they are beautiful. This picture was taken by GeekinSydney on our recent trip to the NSW south coast.

Blue jelly fish on the beach

1 Comment

  1. Congratulations on the way you coped with Covid, cannot report same from this end.
    My compliments to Geekinsydney , the bit of beauty is so blue, so lovely
    Love

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