As nations lift lockdowns and experts worry about a potential second
peak in cases, our ability to ward off infection is one of the hottest
topics of scientific debate.
Ever since it became apparent that children were less vulnerable to
COVID-19 early in the pandemic, scientists have speculated that the
regular spread of benign viruses in places like schools could have
bolstered their immune response to the latest coronavirus.
Now the idea of “cross immunity” among the broader population is gaining some ground.
In a recent post on Twitter, Francois Balloux of University College
London noted an “intriguing” lack of an immediate resurgence in COVID-19
cases following the easing of lockdowns in several countries.
Among the possible explanations, he noted, were seasonality and enduring social distancing practices.
But he posited a “wilder” hypothesis as well — that a “proportion of the
population might have pre-existing immunity to #SARSCoV2, potentially
due to prior exposure to ‘common cold’ coronaviruses”.
Balloux said that might explain issues like cases where there is no transmission between spouses.
Earlier this month, an American study in the journal Cell suggested
between 40 and 60 percent of the population could be immunized against
COVID-19 without ever being exposed to it.
Researchers put this down to the action of protective cells, known as T
lymphocytes, that had been activated by other coronaviruses responsible