Risk needs to be kept in perspective

Views from around the world. These opinions are not necessarily shared by Stuff newspapers.

Every day, people take medicines with known side-effects. The risk is accepted when weighed against the benefit. But Covid vaccines are unfamiliar. There is no record of use over time to build public confidence. Still, they have been tested and proven to offer protection against the virus. By all usual medical standards, they are safe. That remains true for the AstraZeneca vaccine, despite an evolving picture that sideeffects might include a rare blood clotting disorder.

The European Medicines Agency on Wednesday recommended adding blood-clotting to the list of ‘‘very rare’’ side-effects of the AstraZeneca vaccine; not sufficient to require a change in patterns of use.

According to the UK’s Joint Committee on Vaccination and Immunisation, there were 30 cases of cerebral venous sinus thrombosis (CVST), including seven deaths, by March 24, from 18 million people given the AstraZeneca jab. The chance of a severe reaction is probably no higher than 0.0001 per cent, no comfort to those affected, but when it comes to public policy, statistical perspective matters. A very small number is not zero, but nor is it a reason to refuse vaccination.

The human mind pays disproportionate attention to rare events precisely because they are exceptional. Politics often exploits that cognitive weakness.

Politicians like certainties; scientists prefer probabilities. The vaccine challenge is accepting the existence of risk while keeping it in perspective. As long as facts are communicated transparently, it should be possible to process new information and navigate risk without derailing public confidence.