The precautionary principle is not a real-life situation. It tells us not to do something until we’re sure it’s safe. It urges us to err on the side of caution, and not to risk new things that might be damaging. The “weak” precautionary principle rules out things that might just have unquantified risks, but the “strong” one, favoured by the EU, forbids things until they have been proven safe.

Of course, in the real world we can never be sure that anything is completely safe. Everything has associated risks, from climbing downstairs to taking a bath. We might, over time, be able to assess the risk level of innovations, be they drugs, foods, additives or modes of transport. We don’t usually then ban them once they have an established risk level. Instead we assess the benefits of the innovation and calculate if they’re worth the risks involved. This is “cost benefit analysis,” and we do it every day as we cross the road, take a drink, or eat a chocolate. 

On an individual basis we assess whether the gains justify the risk of the possible consequences. When governments take over these decisions, they tend to err on the side of caution, giving more weight to the potential risks than to the benefits delivered. They do this for political reasons, wanting to avoid the wrath of those who might be adversely affected. They tend to do “cost” analysis instead of “cost-benefit,” leaving out the likely benefits.

Many governments, in response to the coronavirus epidemic, have decided that a lockdown will have a better outcome than continued contacts. They’ve weighed up the scientific advice about possible illness and death, and decided that the economic shutdown is the preferred course. They may be right, but the shutdown will have consequences in terms of mental illness, suicide, possible domestic abuse, as well as making people poorer, which seems to increase sickness and lower the quality of life. It’s been a balancing act.

Vaccines against covid-19 have been and are being developed by several teams, and some are in preparatory testing. The process of thorough testing and regulatory approval would usually take years. But there is a strong case for softening the normally stringent regulatory requirements in order to speed up the availability of vaccines. The sooner a vaccine is deployed in large quantities, the more lives can be saved, and the quicker can be the economic recovery. 

Yes, there may be risks involved in rushing an effective vaccine through the hurdles, but the risks of not doing so are almost certainly greater and more predictable. In this case sensible cost benefit analysis should push the precautionary principle to the back seat.