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63% estimate of Covid vaccine by May - Maby Forecast Live


Last week we were joined by UnHerd science writer Saloni Dattani and 41 forecasters on a call to investigate and explore the likely timeline of a coronavirus vaccine.

Before the call, Tom and I narrowed down the scenario that we care about. A vaccine which isn’t widely accepted, approved or available for distribution in large numbers won’t count for much, so in selecting an impactful event we settled on asking about an FDA-approved vaccine available in large numbers of doses in the United States as a scenario which likely indicates vaccine success:

Final question:

When will 25 million doses of an FDA approved vaccine for Covid-19 be available in the US?

Then we decided on the scope. Other public forecasts have asked whether there will be a vaccine before May 2021 as a yes/no binary, but we wanted to have an idea about when that might be if it comes sooner than May. So we decided to ask across five bins:

  1. A: Before Nov 4
  2. B: Nov 4 to Dec
  3. C: Jan to Feb
  4. D: Mar to Apr
  5. E: May or later

The call began with us introducing the concepts and taking the group through a quick calibration quiz. This gave us some data about the group's level of calibration - the better calibrated, the more reliable their forecasts.


Salonium calibration curve

Perfect calibration would mean that the outcome frequency and forecast probability were equal, which wasn't quite the case for our group, but they did better than a lot of groups we have seen recently.

Over time it’s typical to see new forecasters become better calibrated, as they become better acquainted with their own internal sense of probability.

Forecasting - round 1

median forecast initial

We forecast over two rounds. The first round goal was to get the lie of the land among the group, and surface questions for our guest speaker Saloni. The median response for each bin at the end of the first round was as follows:

At the end of the initial round we had a 60% probability the vaccine would arrive before May, with finer grained forecasts on the period in advance of that date.

Each forecaster could submit a comment and/or question anonymously, which were voted for by the group as a whole.


Salonium comments

We then opened the discussion, focusing first on the points most voted for by participants, making sure to cover the standard forecast checklist:

  1. Base rate / outside view / reference class (How do vaccines normally arrive? How do big medical projects normally get organised?)
  2. Inside view, breaking the problem down - what are the steps to this happening, how does the situation in front of us correspond to the base rate / reference class (what's the specific way that a vaccine of this type might progress?)
  3. Scope and scale (is there a difference between 1m, 10m, 25m, 100m doses? What if the time horizon was over a decade?)
  4. Relevant sources- who has been writing on this? Are they reliable? Have we over-reacted/underreacted to recent news (what about the vaccine trial that was halted - is that a big deal?)
  5. Biases - could optimism/pessimism bias play a role? What about political biases? (does Trump talking about vaccines emotionally affect people's forecasts?)

At the end of this discussion we opened forecasting on the update round.


Salonium median forecast

We asked all forecasters to consider the viewpoints and information they’d heard submit an estimate again, altering their response if they felt compelled to by the discussion or some other new information and analysis.

Salonium dot plot

This time the group was slightly more optimistic about the prospects of a vaccine, giving 63% overall to a vaccine before May, most likely in March or April.

Looking at the full distribution of forecasts, we saw that the first round forecasts were more widely dispersed, and it’s easy to identify where the updated forecast became slightly more optimistic.

Lessons Learned

This was our first public test of some of the new app features, as well as our first time forecasting when the team is mostly new to forecasting, and new to each other - our typical client team already knows each other and has worked together before.

With 40 or more people simultaneously forecasting we're glad everything worked according to plan, and we learned a tremendous amount about how to make this work even better in the future - it's all being fed into the design for the next session.

We also collected some benchmark forecasts from other platforms last Thursday (including from our former employers!) so it will be especially interesting to see how things resolve.

Help us improve Maby:

We founded Maby to help any organisation build an efficient forecast capability, and I hope we showed a little of that on Thursday. If your organisation or one that you work with would like be able to produce fast and accurate forecasts then we'd love an introduction, even if they’re not looking to buy anything in right now - we can only make our forecasting knowledge useful if we understand the problems you're facing, so feedback and information is immensely valuable to us as we build our app and systems.

Forecasting Expert vs. Disease Experts

We believe that keeping score of forecasts is the key to assessing and improving your forecast accuracy.

As the covid-19 pandemic hit the United States, we were invited to submit forecast estimates alongside a CDC-funded panel of experts in public health. Our forecasts have been more accurate than virus experts despite having no training in public health, virology, or epidemiology. We simply follow the same sound forecasting techniques that we teach to our clients.

Below you can see a complete record of our coronavirus forecasts.

(10%-90% interval)
Accuracy Score
(Brier score)
(green is better, red is worse)
0.177 0.251
5/10 How many cases per day will Washington state average for the week ending June 7? 170
155 0.289 0.713
5/10 How many confirmed US cases will there be on May 17? (in millions) 1.48
1.48 0.062 0.135
5/10 How many deaths will Pennsylvania report as of June 13? (in thousands) 7.6
6.2 0.214 0.180
5/3 What will the 7 day average new cases be in Texas for the week ending June 13? 1150
1779 0.323 0.166
5/3 How many US COVID deaths will occur in 2020? (in thousands) 160
5/3 How many confirmed US cases will there be on May 10? (in millions) 1.33
1.33 0.066 0.129
5/3 How many US states/territories will report more new cases for September compared to June? 7
4/26 How many confirmed US cases will there be on May 3? (in millions) 1.14
1.152 0.174 0.195
4/26 When will weekly new US deaths first fall below 5,000 (Sunday to Saturday)? 5/23
6/20 0.376 0.158
4/26 What will the average new daily cases be for Georgia between 5/10 and 5/16 inclusive? 900
659 0.159 0.173
4/19 How many deaths due to COVID-19 will occur in the US in 2020? (in thousands) 80
4/19 As of May 9, how many COVID-19 related deaths will have occurred in the US? (in thousands) 56
73 0.420 0.170
4/19 As of May 9, how many COVID-19 related deaths will have occurred in Illinois? (in thousands) 2.4
3.3 0.294 0.170
4/19 As of May 9, how many COVID-19 related deaths will have occurred in Louisiana? (in thousands) 1.85
2.2 0.129 0.170
4/19 How many confirmed US cases will there be on April 26? (in thousands) 930
959 0.222 0.127
4/12 How many US COVID-19 cases will there be on April 19? (in thousands) 755
751 0.093 0.151
4/12 How many US COVID-19 deaths will occur by May 1? (in thousands) 50
59 0.111 0.180
4/12 How many states will report more than 1000 deaths by May 1? 12
14 0.193 0.712
4/12 Which of the next 6 months will see the highest total number of deaths nationwide in the US for COVID-19 illness? April
April 0.037 0.108
4/12 How many US COVID-19 deaths will occur by June 1? (in thousands) 71
99 0.178 0.180
4/5 How many US COVID-19 cases will there be on April 12? (in thousands) 520
551 0.103 0.336
4/5 Which month (March-August) will see the highest total number of hospitalizations nationwide in the US for COVID-19 illness? April
April 0.043 0.370
3/29 Which month (March-August) will see the highest total number of hospitalizations nationwide in the US for COVID-19 illness? April
April 0.137 0.344
3/29 How many deaths due to COVID-19 will occur in the US in 2020? (in thousands) 240
3/29 Will NY state report fewer than 1,000 new cases on the day of April 28? 28%
no 0.157 0.500
3/29 How many US COVID-19 cases will there be on April 5? (in thousands) 410
332 0.123 0.145
3/22 Will US COVID-19 deaths exceed 245,500 by the end of 2020? (percent probability YES) 45%
3/22 Will there will be a second wave of US cases in 2020? (US active cases declines by 50% and subsequently increases by 50% AND 2nd wave must be at least 50% as high) (probability YES) 52%

Click here to see how the Brier scores were calculated.

Build your team's forecasting capabilities

Maby helps your team produce accurate forecasts using our custom software, expertise in forecasting best practices, and experience making forecasting practical for busy organizations. Gain the confidence that you know the what top organizations are already doing.

calibration curve demo dot plot demo

Goals: We’ll work with you to identify the most important estimates for your organisation. From project completion dates, key risks, quarterly outlook projections, we compile a register of required estimates.

Training: We can offer as much or as little training as you require. For some clients, building up their in-house forecasting capacity is the most important goal. Other clients prefer monthly sessions.. Either way, we have feedback and training tools to improve your team’s forecasts, and avoid the risk of common cognitive biases which can throw off estimates.

Facilitation: We’ll gather your team and walk them through the estimates they need to make- harnessing the wisdom of your crowd. Our process and software to rapidly record, anonymise, share and aggregate information. We find that 15 minutes per topic is enough to see measurable improvement in accuracy. Want an outside view into your future timelines? We can supply expert forecasters to join your team and add their insights.

Reporting: At the end of the process, you will receive a full report of every estimate, aggregated for accuracy, with qualitative commentary drawn from your team’s comments. Each participant will receive a report of their own estimates for future review, and we can check back in and update the forecasts as new information comes to light.

Feedback and improvement: For longer run projects, we can gather multiple forecasts from your team and offer detailed feedback as forecasts resolve - from calibration to resolution to noise and bias reduction, we can help your team improve their predictive accuracy over time, creating a valuable in-house resource for you to call on any time you’re facing uncertainty.

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