Will variants cause new lockdowns for the US or UK this year?

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Covid vaccination is moving forward in the UK and US at a rapid pace, but new variants are constantly emerging with the potential for vaccine escape. So this week we looked at whether we’re likely to see new lockdowns in 2021 in the US or UK caused specifically by covid infections among the vaccinated. (we may look at whether vaccine progress will stall in a future edition- for this week we assumed that vaccination pace will continue).

Our median estimates: a 12% likelihood of national UK lockdowns caused by infections among vaccinated people, and 13% likelihood of a statewide lockdown happening in at least one state in the US for the same reason.

First, defining terms- the UK’s current state of partial, ongoing restrictions with no stay-at-home order does not count as a lockdown, nor do mask mandates; we’re really interested in the most costly measures: a stay-at-home order.

Forecasting on future lockdowns subsumes a number of lower-order questions, some fuzzier than others. Will a largely vaccine-escaped variant emerge? What about the willingness of lawmakers to order more lockdowns? Does the answer change when you have a large percentage of the population vaccinated with a slightly less effective vaccine that may be less resilient versus new variants? In the event of a new variant causing havoc, how quickly could modified vaccines be manufactured and distributed, thus mitigating the need for lockdowns? Could existing vaccines be used as heterologous booster shoots to keep antibody titres sky-high? 

This was all quite tricky for us, because there’s no obvious reference class. Looking to how lawmakers reacted last year isn’t especially informative. Lawmakers will likely behave very differently once most of the population is vaccinated, or has been given the opportunity to get a vaccine. Even when confronted with death tolls several times greater than a bad flu season, the public and their representatives alike may prefer to bite the bullet and accept high mortality concentrated amongst the unvaccinated, confident that vaccines will keep the majority safe. 

A closer look at the forecasts.

As always, we followed the Delphi method- anonymously collecting the first round of forecasts (shown in blue) and comments, discussing and reviewing, then collecting another anonymous round of estimates (shown below in red).

Here’s the distribution of forecasts on the likelihood of a US statewide lockdown caused by covid cases among the vaccinated:

From the comments, you can see very similar reasoning leading to divergent forecasts:

28%: There are lots of states in the US - 50! We only need one to lock down. However, lots of lockdowns have been enforced by cities in the US. One idea is the most vaccinated states are more likely to lock down as they are taking covid more seriously, but there is the cases/hospitalisations link. Variants are undoubtedly going to come up throughout the rest of 2021, but the origin is not likely to be in the US/more vaccinated countries, and then they have to get to the US. Boosters against variants are on order and production is seemingly high, therefore I think there is a risk this will happen in some blue states, but broadly am hopeful this won't happen.

Contrast with:

6%: Factors pushing me towards single digits:

1. Nearly all US vaccinations done w/most effective vaccines (Pfizer, Moderna)

2. Uncertain but not super high probability of a vaccine-escaped variant emerging and spreading in the US over this timeline anyway

3. Lockdown weariness

4. Possibility of much faster vaccine development and production this time around, making lockdowns less likely as policy response vs surge vaccinations even in the event of a bad variant emerging?

Of course, individual forecasters - even generally well-calibrated ones - generally have a slight bias towards underconfidence or overconfidence, so it’s not surprising that faced with such a complex question with no real reference class, we see forecasters A and B thinking similar things but giving very different estimates.

The team ranked the probability of a national lockdown in the UK by the end of the year as almost identical to the probability of a single statewide lockdown in the US:

From the comments:

7%: The UK is much smaller than the US so a national lockdown is a much bigger deal than a statewide lockdown. On the flip side, a very high % of the population is vaccinated with a somewhat lower-efficacy vaccine (AstraZeneca) which is probably easier for variants to escape from (as perhaps partially demonstrated by SA variant)

Against that, however, there are already plans for booster jabs underway, using both more effective vaccines than the AstraZeneca shot (more Pfizer jabs, Novavax) and it seems also a new version of the AstraZeneca vaccine specifically targeting the SA variant (although will this need a whole new viral vector due to acquired immunity vs the vector?)

Again, compare to the similar logic, but very different estimate given by another forecaster:

21%: The UK is widely vaccinated with Oxford/AstraZeneca which is likely to be less effective against variants than Pfizer and Moderna. The need to control outbreaks for travel to the EU may be a larger driver of a decision to be proactive. Current politics goes against lockdowns and is unlikely to change significantly before the end of the year.

All together, we’re looking at a pretty low likelihood of more lockdowns from vaccine escape at an individual level- our group of forecasters mostly agrees that rapid booster deployment, a lockdown-weary public and perhaps altered tradeoffs around virus deaths compared with 2020 mean that freedoms will most likely not be restricted again to the levels they have been in recent times. But for governments, a greater than 10 percent chance of future lockdowns is the kind of thing to justify some planning time.

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Next edition, we’ll be looking to the Taiwan Strait- if you have a suggestion for a topic you’d like to see, or to vote on the topics you’d like us to cover, we’re all ears!