Lockdowns work. That’s the evidence from many different countries now, including Australia. To be more precise, lockdowns reduce the effective reproductive rate of the virus to the point where it is below 1, meaning that, on average, each infected person passes the disease on to less than one other person. As long as this is sustained, the number of new cases will keep declining, as we have now seen. Potentially, as has been claimed to be the case in China, it will reach zero.

Although some people are still talking about “flattening the curve”, it now seems clear that the best strategy is (near) eradication, pushing the number of infections down to (or near) zero, and preventing any resurgence. But what comes next?

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As soon as the government released its modelling of the pandemic a few days ago, I realised something was badly wrong. The modelling showed infections increasing even under lockdowns, which obviously wasn’t happening. The crucial parameter here is R, the number of new infections generated by each existing infection. If R is greater than 1, the number of infections grows exponentially, but if R is less than one, it declines, eventually approaching zero. The knife-edge case is R=1, when the number stays constant.

On checking the paper on which the modelling was based, I found that it did indeed assume R>1, even with social distancing. This was less surprising when I realized it was based primarily on data from the initial outbreak in Wuhan, before the lockdown in China had taken full effect. (I later discovered that the report had been given to the government in February, which makes its release now rather pointless).

I quickly drafted an article explaining the importance of R and the fact that the modelling was out of date. I thought it would attract plenty of interest, but in fact it was very difficult to place. A lot of editors were unwilling to challenge the government on this. I eventually managed to get it run in Inside Story.

My time outside the tent didn’t last long. Today, the Deputy CMO Paul Kelly gave an analysis that matched mine almost exactly, and effectively abandoned the “flattening the curve” strategy in favour of eradication. The only difference is that he thinks R is “on the cusp of” falling below 1, while I think it’s already there. Some conservativism is called for here.

This has been the whole story of the pandemic for me. Almost every time I’ve criticised the government for not doing or saying something, they’ve got it right (or nearly right) a day or two later. Compared to my usual experience of waiting years for any kind of vindication of my argumetns on policy, it’s a strange feeling.