University of Amsterdam researchers followed 10 volunteers for 35 years and tested them every month for four seasonal and weaker coronaviruses, which usually cause mild illnesses similar to the common cold.

They found those who had been infected with the strains — from the same family as SARS-CoV-2, the type that causes Covid-19 — had ‘an alarmingly short duration of protective immunity’.

Levels of antibodies, substances stored by the immune system to allow the body to fight off invaders in the future, dropped by 50 per cent after half a year and vanished completely after four years.