Why Covid elimination remains the best game-plan

Here in Aotearoa, we’re playing Covid-19 in “elimination” mode. Some countries are trying “suppression” mode, while others are running with what seems like “survival-of-the-fittest/wealthiest” mode. Over the last few weeks, I’ve been getting messages from people who don’t think our elimination game-plan is going to work. Some of them point to the fact we are currently experiencing an outbreak. Others send links to interviews with experts from “survival-of-the-fittest/wealthiest” countries, like the UK and the US. And others mention “flu” and the “common cold”. Is any of this evidence our strategy is failing or the wrong one for us to be following?

I’ve explained before why I support elimination, but let’s start by making sure we are all on the same page about what elimination actually means for Covid-19. Because unfortunately, elimination is one of those tricky words that means different things to different people. When epidemiologists use the word eliminate, they mean to bring the disease under control and reduce cases to zero in a particular geographical location. Of course, when anyone who isn’t an epidemiologist hears the word eliminate, they understand it to mean to completely remove or get rid of something. The word epidemiologists use for that is eradication.

So, let’s be clear.

Of course the reality is that even with the best processes in place, those facilities are not surrounded by a magical forcefield that can be 100% guaranteed to keep the virus from sneaking out. Hence our latest outbreak. There are clearly areas we can improve on, but I think we should be proud of the fact that thousands of people have been through our facilities and this is the first time in months we’re seeing community transmission. And hopefully we’ll have it stamped out very soon.

Moving on to the overseas experts. Many are saying lockdowns don’t work. One of the problems is the definition of lockdown itself. Everyone throws that word around and yet it’s really clear one country’s idea of “lockdown” is another’s “only a little bit restricted”. It’s quite obvious that elimination is a pipedream when your country has been playing in “survival-of-the-fittest/wealthiest” mode since the beginning of the pandemic. The more community transmission, the harder it is to bring an outbreak under control. It’s not impossible. Just harder. But that is not the situation in New Zealand. I cannot tell you how many messages I’ve had from my counterparts in the UK and the US who wish their governments had taken the approach ours did.

Yes, I know they are caused by viruses but that’s like comparing apples, oranges, and bananas. For starters, there are hundreds of different viruses that cause the common cold. There are the rhinoviruses of which there are three main species but over a hundred different types. Then there are the adenoviruses of which there are several species and again multiple types within those species. As an aside, adenoviruses are being used as a backbone for some of the Covid-19 vaccines. There are also four species of human coronavirus. These are not to be mistaken for the coronaviruses that cause Covid-19, SARS, and MERS.

But wait, there’s more! Human respiratory syncytial virus. Human metapneumovirus. So yeah, to get rid of the common cold we’d need a hell of a lot of vaccines.

As for the flu? That’s caused by the influenza virus of which there are four species and various subtypes. Influenza viruses undergo what’s called antigenic drift and reassortment. Influenza viruses mutate quite a lot – nearly every new influenza virus that’s made by a cell will have one mistake. These mistakes mean that the proteins recognised by our immune system change over time. That’s antigenic drift. The mutation rate for the virus responsible for Covid-19 is much, much slower. Reassortment is what happens when two different influenza viruses infect the same cell and their genetic material gets mixed as it’s packaged into the newly made virus particles. Antigenic drift and reassortment are why we need a new vaccine every year.

To eliminate the flu, we would also have to stop it circulating in other animals. Just check out the number of different animals besides humans that the influenza viruses can infect. I don’t fancy our chances vaccinating all of those animals.