February 4, 2021

expert reaction to non-peer reviewed modelling presented on a dashboard suggesting that herd immunity may be reached in the UK in July if the vaccination programme stays on track

The summary dashboard, based on modelling at University College London (UCL), suggests herd immunity may be reached in the UK by July if the vaccination programme stays on track.

Prof Mark Woolhouse, Professor of Infectious Disease Epidemiology, University of Edinburgh, said:

“At the present time it is very difficult to estimate when or even if the UK’s COVID-19 vaccination programme will bring us to the herd immunity threshold.

The UCL study estimates the extent to which vaccination interrupts transmission which is one – but only one – of several unknowns about the long term impact of the vaccination programme.

The report highlights that the herd immunity threshold could be reached in July. However, this is very uncertain indeed. According to the model it could be as early as late May. More pessimistically, it might not be possible to reach the herd immunity threshold at all.

Failing to reach the herd immunity threshold would not mean that COVID-19 could not be controlled. But it would require additional measures.

The nearer we can get to the herd immunity threshold then the less we will need those additional measures.

It is still too early to say with confidence what the long term impact of the vaccination programme will be. The UCL study – and others – will make the picture clearer over the next few week.”

Dr Adam Kucharski, Associate Professor in Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, said:

“Unfortunately, the modelling approach used to produce this analysis has a history of making over-confident and over-optimistic predictions. In early September, a pre-print claimed that, ‘The best model of UK data predicts a second surge of fatalities will be much less than the first peak (31 vs. 998 deaths per day, 95% CI: 24-37) – substantially less than conventional model predictions.’ In late September, the lead author claimed, ‘When one models what is likely to happen – in terms of viral spread and our responses to it – a plausible worst-case scenario is a peak in daily deaths in the tens (e.g. 50 to 60) not hundreds, in November. This may sound rather precise; however, this kind of modelling has already proved to have predictive validity to within days.’

“There is currently a lot of uncertainty about vaccine effectiveness on reducing transmission, the duration of vaccine protection, characteristics of new variants, and the future control measures countries may keep in place or relax. However, it is not clear from the online model description how it incorporates these uncertainties, or what has been updated since it made its predictions above. Models can be a useful tool for exploring potential dynamics under different assumptions about transmission and control measures, but it’s crucial that these assumptions are made clear, and known biases in past model performance are addressed before new results are publicised.”

https://www.fil.ion.ucl.ac.uk/spm/covid-19/forecasting/

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www.sciencemediacentre.org/tag/covid-19

Declared interests

None received.