Without zero-COVID, will cases surge in China?

Key takeaways:

• When the zero-COVID policy becomes unsustainable, we expect a major death toll among the 80+ population in China.
  • The reason: Low vaccination rates, less effective vaccines than in other countries, and no widespread availability of antivirals.
• What can be done to minimize the death toll?
  • Try to increase vaccination rates in the 80+ population, including use of more effective vaccines.
  • Increase availability of antivirals.
• Until now, China has avoided major outbreaks, leaving the population largely susceptible to new infection. Higher rates of infection also increase the probability of new variants developing.
  • New variants may not be more severe than past ones, as was the case with Omicron sub-variants.

This transcript has been lightly edited for clarity

High death toll expected in 80+ population

In this week’s Global Health Insights, I would like to address the question of what we think is going to happen in China. During the past year, trying to model the course of the epidemic in China has been extremely challenging. When we saw Omicron pass through Hong Kong, the surprise to many was the large number of deaths in the elderly, and at the root cause of Omicron’s toll in Hong Kong was that in the over-80 population particularly, there was relatively low vaccine coverage because of lack of confidence in some aspects of vaccination.

And so the question comes, what will happen in China when there is widespread transmission of Omicron? And at various points, we have predicted that this would happen in the spring or in the summer or in the fall, given the economic costs of pursuing the zero-COVID strategy.

Now, many people have expected that China would ease the policy once the party Congress was over. And again, we’re hearing rumors that there may be a shift away from a zero-COVID strategy.

But the basic Hong Kong problem still exists in China: you have a substantial fraction of the over-80 population, in almost every province, that is not vaccinated. In the rest of the population, you have a vaccine that has less effectiveness than some of the mRNA vaccines that many other countries have used. And there is not widespread availability at all for antivirals, such as Paxlovid.

So we do expect that at the point, at some point in the future, when it’s unsustainable to continue a zero-COVID strategy, there will be widespread transmission of Omicron, and that will actually have a considerable death toll in the over-80 population.

What can be done to minimize the death toll when the zero-COVID strategy ends?

Now, things can be done to manage this, given we do expect you can’t maintain that forever, or we don’t believe you can. Then the question is, can you slow the transmission and keep the burden on the health system at a more manageable level, so that hospitals are not overwhelmed?

And that’s one of the options that are available, using some less restrictive, but still some form of mandates to slow Omicron transmission. There’s already pretty widespread mask use, so that’s not going to change very much of the trajectory.

The other strategy or option is would China change course and actually try to vaccinate, particularly the older population, with the more effective mRNA vaccines? But even there they still have the fundamental problem of lack of trust in that population with the vaccines, even the Chinese-made vaccines. And it’s not at all clear that there will be enough trust to get high enough vaccination coverage to avoid the death toll in that age group.

And then lastly, is the strategy of trying to acquire and have antivirals available, particularly for that high-risk group, the over-80s.

Implications of widespread infection for immunity rates

However we look at it, it’s very likely that the next few months are going to be quite challenging for China. If we’ve learned anything from our systematic reviews around the patterns of resistance after infection, it’s that infection with different strains of the virus does induce considerable immunity that lasts, for preventing death, quite a long time, and for preventing infection, quite a long time, as long as there isn’t a new sub-variant that comes along.

And in fact, our systematic reviews do show, and we expect they will be coming out more publicly in the near course, that the immunity from natural infection is as good as and longer sustained than immunity from vaccination. So put that together, it means that the populations at greatest risk in the world are those that have avoided a lot of transmission and have gaps in vaccination. And that’s exactly the case for China.

Potential for new variants to develop

So there’s always the concern around the large volume of transmission leading to an increased probability of new variants. And certainly that has to be true at some statistical level, that if you have billions of infections, you’re more likely to see new variants emerge.

But it’s not clear how big an issue that is because all the people who are susceptible in China will eventually get infected. Are we better off seeing that spread over six months, or nine months, or three months, or two months? Not clear, since risk of a new mutation, for example, is proportional to the number of infections.

The news that should make us less alarmed is that we’ve had billions of Omicron infections this year and yes, we have seen new sub-variants emerge – BA.2, BA.5, XBB, B.111 – but none of them have been a dramatic change. They’ve had some immune escape, but they have not had increased severity.

So we don’t know, of course, but it’s not as if having a concentrated period of  half a billion infections is really that different from having it spread over a few more months, which would happen with stronger controls on transmission.

As we look forward there’s also the risk that as time goes by, the natural immunity from, for example, the huge Omicron wave that infected so many people in the world, will start to wane and we will start to see more people at risk of future sub-variants of Omicron or other variants, which could be more concerning.

And so it’s not as if the only place in the world that’s at great risk is China. It’s just that that’s the biggest concentration right now for that at-risk population.

So it’s a situation for which there’s no obvious solution because neither the zero-COVID strategy forever is going to work, nor is there any indication that China will try to deploy better vaccines or have access to antivirals.

And that leaves us in this situation where it’s probably going to be a balancing act they pursue of trying to have transmission and having it be slower. And so that is the situation we find ourselves in for COVID in China in the coming months.