Judging vaccination success requires numbers, not guesswork

BY George Yarrow | tweet george_yarrow   /  12 January 2021

There is no doubt that hospitals are currently under severe pressure, particularly in those regions of the UK where the new variant of the virus has made most progress. But there are reasons to challenge the ever-pessimistic views of the Chief Medical Officer when he states that the vaccination programme is going to take several weeks for its effects to be felt.

The programme started on 8 December and, although numbers were relatively modest to begin with, considerable progress had been made by the end of the year in vaccinating those in the most vulnerable groups. Although the vaccines take some time to build up to maximum effectiveness, their ‘training’ of immune systems begins almost immediately. While the training may be insufficient to prevent infection and disease, it may nevertheless mitigate the severity of an early, post-vaccination infection.

There is, therefore, a possibility that December vaccinations are already beginning to have benign effects on hospitalisations and deaths and that we will not have to wait weeks to begin to evaluate those effects. If so, that has major implications for public policy.

It is often pointed out that UK policy has been behind events since the beginning of the epidemic and there is plenty of evidence to support that proposition. With a greater foresight that allows for the development of reasonable expectations about the future course of things – going beyond the speculative ‘what ifs’ of epidemiological models and the enduring pessimism of the medical advisors – it would be possible to plan ahead for the liberalisation that is hopefully destined to come. Such planning could aid the development of economic and social policies, not just Covid policies.

Given these points, I have suggested a simple metric, now published daily on Twitter, to assess the emerging effects of the vaccination programme. It compares the number of Covid-related deaths of over 80s each day to the number of deaths of those in the 60-79 age bracket. Specifically, it records the percentage deviation of the over 80s rate from the 60-79-year-old rate in the mortality data published daily by NHS England.

The argument behind it is straightforward. In the first phase of the vaccine programme it is the over 80s who are being vaccinated in substantial numbers, whereas the 60-79 years will have to wait a while. The effects of vaccination should, therefore, show up first in reduced mortalities among the over 80s, leading to a fall in the percentage deviation.

The approach is clearly open to elaboration – for example, by examining relative hospitalisation rates for the two groups or extending to deaths outside hospitals – but its simplicity at least gets the ball rolling. The approach focusses on objective numbers that reflect the impacts of a policy programme, rather than speculative projections from models resting on myriad assumptions or on prognostications devoid of evidential support – like propositions about the effects of restrictive social measures on Covid cases which, over the course of ten months now, have still never been subject to rigorous, empirical evaluation.

The results of the exercise are shown in the diagram above. The latest observation, for 11 January, is striking. A quick check suggests it is the lowest recorded number since 1 December 2020, which itself was an exception at the time.

Will we have to wait weeks to see the effects of the vaccines? We will likely have to wait a few days (not weeks) to see more clearly, but it should be a straightforward empirical matter, requiring no call for the guesswork that has been so characteristic of public announcements to date.

The writer is the former chairman of the Regulatory Policy Institute and emeritus fellow at Hertford College, Oxford.



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