Allen Cheng Profile picture
ID physician, epidemiologist/statistician. Past President @ASIDANZ. Opinions my own. RT ≠ endorsement
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Jul 13, 2021 12 tweets 3 min read
Hi @Jan__Fran. I won't try to give you medical advice without knowing your personal circumstances, but I'm sorry that you've had a difficult time seeking advice. I'd thought I'd talk you through the advice ATAGI provided today about vaccines for people in Sydney at the moment.
health.gov.au/news/atagi-sta…
Jul 3, 2021 11 tweets 4 min read
I've been off Twitter for a few months, but just a brief note to confirm that I've completed my secondment to the Victorian Dept of Health and will be resuming my usual roles at Alfred Health and Monash University
The last few weeks across Australia have been a reminder that COVID isn't close to over yet, and I'm sure there will be many challenges to come as we navigate our way through the next stages of the pandemic.
Apr 10, 2021 6 tweets 2 min read
Hi @bruce_haigh - I can't help with the politics, but I might be able to help with the maths. As a person in their 70s in Australia, if you had gotten COVID last year, on average you'd have a 38% chance of being hospitalized, a 7% chance of going to ICU, and a 10% chance of dying.
Apr 8, 2021 25 tweets 5 min read
OK, has been a long week but will try to explain the ATAGI statement published tonight
health.gov.au/news/atagi-sta… Like with all medical treatments, when we have a choice we need to consider the risks and the benefits. In this case we're thinking about the risk of a side effect due to vaccination and the benefit of a reduced risk of COVID.
Jan 12, 2021 23 tweets 5 min read
Why would we use a vaccine that mightn't prevent transmission? Should we use one particular vaccine, or roll out the vaccines we have as broadly and quickly as possible? I'd argue that we should use all available vaccines that prevent COVID, even if they don't reduce transmission as much as we'd like.
Jan 4, 2021 25 tweets 5 min read
I'm seeing commentary asking why Australia isn't just rolling out the vaccine prior to regulatory approval, or why the TGA just doesn't register the vaccine based on approvals in other countries. A thread on what's involved in vaccine regulation. (I'm the chair of the Advisory Committee for Vaccines, which is appointed by Minister Hunt. It's the TGA's responsibility to assess drugs and vaccines but this committee provides advice)
Dec 20, 2020 17 tweets 3 min read
A few comments on endpoints for COVID vaccine trials. For regulators, the main question when considering effectiveness is whether the vaccine reduces the risk of symptomatic COVID. But there are two other relevant questions - whether a vaccine prevents severe disease, and whether it prevents transmission.
Jul 15, 2020 23 tweets 5 min read
A thread about the SARS-CoV-2 vaccines in development. There are a lot of candidate vaccines in development, but we still have a long way to go. Vaccines work by training the immune system on a virus or a component that doesn't cause disease, so that it can respond more efficiently when it sees the real thing.
Jun 16, 2020 22 tweets 5 min read
SARS-CoV-2 infection in patients that don't have symptoms. It's complicated. A thread. Data suggest that viral load does start to increase and is maximal slightly before the onset of symptoms, although there is clearly a lot of variation between patients.
nature.com/articles/s4159…
May 29, 2020 15 tweets 4 min read
A large group of us have expressed concern about The Lancet HCQ/CQ study (10.1016/S0140-6736(20)31180-6). @TheLancet
zenodo.org/record/3862789… There are many criticisms and anomalies, but a few notes about the Australian data. The authors reported 609 admissions and 73 deaths in 5 Australian hospitals on 21 April.
May 9, 2020 16 tweets 5 min read
Where are we now in Australia and what might we expect next? Over the last week, there have been about 20 cases/day reported across Australia, but jurisdictions other than NSW and VIC have very small numbers of cases. NSW cases relate mainly to the outbreak at Newmarch House aged care facility, and Victoria to Cedar Meats, with secondary transmissions from this cluster.
abc.net.au/news/2020-05-0…
Apr 29, 2020 9 tweets 3 min read
There is often confusion about the terms eradication, elimination and control, and these terms are particularly confusing when applied to COVID.
who.int/bulletin/volum… Eradication is the permanent reduction to zero of the worldwide incidence of infection. This was achieved for smallpox - we no longer need smallpox vaccination. This isn't going to happen anytime soon for SARS-CoV-2.
Apr 26, 2020 17 tweets 4 min read
About how the Australian COVIDSafe app helps with contact tracing. A thread.
This is from the perspective of an epidemiologist - I don't have any expertise on the technical or privacy aspects.
health.gov.au/resources/apps… Contact tracing is a manual process. The local state/territory health department routinely calls up people that have been diagnosed with COVID once they are notified.
Apr 7, 2020 10 tweets 2 min read
A second thread to explain how the #COVID19 modelling works. (Stephen Hawking was once told that each equation in his book would lose him half his audience. If the whole Australian population were potential readers, there'd be 6 people still reading to the end of the technical appendix)
Apr 7, 2020 23 tweets 5 min read
The Australian #COVID19 modelling was published today. My thanks to James McCaw (@j_mccaw) for checking this thread. I’ll do two threads - one explaining the results and how we might interpret them; and another to try to explain how these models work. Disclaimer: my contribution to the paper was to fact check some of the parameters and to help with the interpretation. This is the result of hard work by Jodie McVernon, @j_mccaw, @rob_mathbio their team with extensive experience with these complex methods.
Apr 4, 2020 24 tweets 4 min read
The PM has indicated that the Australian #COVID19 modelling will be published during the week. A thread (part 2; note part 1 with my disclaimers)
There are going to be two instinctive reactions to the studies, both wrong.
(These are the reactions I have to every model I see, even with some experience in looking at them)
Mar 27, 2020 20 tweets 5 min read
A thread about epidemic modelling, prompted by calls to "release the modelling" and the MJA paper. #COVID19 Disclaimer: I'm an epidemiologist and ID physician. I have published the occasional mathematical model. I wouldn't dare call myself a modeller - this is a highly specialised area within ID epidemiology.
ncbi.nlm.nih.gov/pubmed/30309313
onlinelibrary.wiley.com/doi/abs/10.111…
Mar 20, 2020 15 tweets 3 min read
Getting a lot of questions about rapid tests for COVID. Just a short thread about the various types of tests available or in development. #COVID19 Disclaimer: I'm not a lab person and others (@MackayIM @kedzierskalab @drdebwilliamson) may want to correct me
Mar 18, 2020 10 tweets 2 min read
A (very long) AHPPC statement on current epidemiology, social distancing, schools and universities, aged care facilities and community sport #COVID19 OK, the Twitter version...
Most of the Australian cases to date are still linked to overseas travel or in their contacts, so the current growth reflects the exponential growth in cases overseas, rather than uncontrolled local spread
Mar 8, 2020 21 tweets 6 min read
A brief thread about what might be coming up in Australia to control #COVID19. I'll emphasise that what interventions are likely to work depend very much on the situation at the time, and not all are being considered in the near future, or even at all. Some principles are that interventions should be proportionate to the risk, reasonable and the least restrictive option, considers equity and burden, and evidence based. This obviously is difficult with uncertain parameters and imperfect surveillance.
Feb 28, 2020 10 tweets 3 min read
I've been getting questions from my non-ID hospital colleagues about what they need to do about #COVID19.
You can reassure them that there is no evidence that COVID-19 is circulating in Australia now. They don't need to do anything differently, but things are likely to change. 1. Be informed from credible sources. There's enough misinformation going around and your patients may ask you questions. The Australian and state/territory government, WHO, CDC, ECDC sites are all good (ID physicians use ProMed)
promedmail.org