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The most common question being asked right now is, “when are we going to go back to normal?” We would love dates and we would love certainty. Businesses want to reopen, people want to socialise and see family members they haven’t seen in a long time and we all want to resume our sporting and cultural lives. In early December, the question for many was whether we could have a normal Christmas. This focus on a particular date had disastrous consequences for us all.
This week, UK prime minister Boris Johnson published his roadmap to bring England out of the countrywide lockdown that has been in place here since Christmas. Despite the modelling group of the Scientific Advisory Group for Emergencies (SAGE) committee explicitly advising against it, Johnson published a roadmap with dates attached.

If we want to avoid repeats of the catastrophic surges in viral numbers and subsequent lockdowns that were seen in late December and all through January, then it’s clearly safer to stick to data and not dates

Johnson’s dates were couched in terms of the “earliest possible date” or “not before”. However the UK public have taken them to heart as definite dates for openings. Gyms are currently emailing their clients telling them that they will open on March 29th, pubs and restaurants have signage in their windows saying they will be open for business on April 12th. The organisers of the Reading and Leeds festivals, which attract crowds of more than 100,000, are advertising that the festivals will go ahead on August 27th-29th. It would be an understatement to say that the roadmap announcement with definite dates attached has been very well received by much of the British public. In fact, euphoria might be a good adjective to use in some cases.
It is possible that these dates will end up being fine but if we want to avoid repeats of the catastrophic surges in viral numbers and subsequent lockdowns that were seen in late December and all through January, then it’s clearly safer to stick to data and not dates.
It is axiomatic at this stage to say that all bad things come from high viral transmission rates. Within weeks of transmission rates rising, hospitalisation rates and rates of mortality increase and restrictions on our freedoms follow with monotonous regularity, and last for a long time. Nobody wants that.
The source of all the optimism and euphoria is found in the highly efficacious vaccines that have been developed. A half dozen are in widespread use around the world, with several more in the process of being approved for use. Many have demonstrated efficacy levels that we could only have dreamed of six months ago. Polio, by comparison, was pushed to extinction by a vaccine that was only 80 per cent efficient, while some of the new Covid-19 vaccines have efficacy rates above 90 per cent. For most people, this is evidence enough that the vaccine on its own will return us to normality. The reality, if we are not careful, might be somewhat different.
Normality is taken by most of us to be a situation where there are no artificial restrictions being placed on our movements or activities. A situation where the virus is being controlled solely by the immune systems of the population.
In order to surpass the threshold for “herd immunity”, we need to have a certain proportion of the population immune to the circulating virus. This proportion is dictated in large part by transmissibility of the virus – the now-famous R0 (pronounced R naught). This number is not the “R number” being quoted daily in briefings, and which is seen to swing up and down with every change in the rules of lockdown. Rather it is the transmissibility of the virus in a situation where there are no other restrictions or controls in place.
Since 1970, we have known that there is a simple relationship between R0 and the herd immunity threshold. A rule-of-thumb calculation for the B117 variant that is dominant in Ireland would suggest that the threshold for herd immunity is at least 78 per cent. This means if more than 78 per cent of our population was immune to all variants of Covid-19, then we could expect the pandemic to go into decline without any other intervention. Normality, as defined above, could be restored.
The difficulty for Ireland resides in the 10-12 per cent of people that cannot be vaccinated because of health or age reasons and if we are to believe the recent poll in The Irish Times, 14 per cent of the Irish population have indicated that they would not take any vaccine. Also, even if we assume that vaccine efficacy is as high as 90 per cent against all variants – and this is unlikely to be the case – this would leave significant numbers of people susceptible.

If we remain focused on data and use it to drive viral numbers as low as possible, then we can have a summer that looks somewhat like the summer of 2019

In the UK, the SAGE group has reported that, for the reasons outlined above, it expects no more than two-thirds of the population to be immune at the end of the vaccine rollout, leaving more than 20 million people susceptible and herd immunity still a long way off.
These numbers leave us with problems. Even if new variants do not arise with even greater transmissibility than the current variants, we are very unlikely to see global herd immunity any time in the near future. Yes, the vaccines will do a lot of the heavy lifting but the mathematics are against us right now.
Decision-making on easing restrictions, dealing with viral imports through travel and responding quickly to the characteristics of new variants should be entirely based on data and not dates. High levels of community testing and contact tracing for positive cases must continue long into the future. Outbreaks, when they occur, must be identified early and ruthlessly stopped. Financial support must be made available for those who need to isolate, so they don’t have to make the choice between staying home and going to work.
Large sporting and cultural events, if they go ahead at all, should be planned with the virus in mind. SARS-CoV-2 virus doesn’t understand dates and attaches no particular significance to the day of the week or the week of the year. If we remain focused on data and use it to drive viral numbers as low as possible, then we can have a summer that looks somewhat like the summer of 2019. We could see recovery in the economy and the return of sporting and cultural events. Whereas if we focus on dates we risk having a summer as disastrous as January of 2021.
There are reasons for huge amounts of optimism but we need to learn from the mistakes of the past. Stick to data, not dates.
James McInerney is head of the School of Life Sciences at the University of Nottingham