Studies suggest Omicron is less severe because lungs are spared

A spate of new studies on lab animals and human tissues are providing the first indication of why the Omicron variant causes milder disease than previous versions of the coronavirus.

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NEW YORK

In studies on mice and hamsters, Omicron produced less-damaging infections, often limited largely to the upper airway: the nose, throat and windpipe.

The variant did much less harm to the lungs, where previous variants would often cause scarring and serious breathing difficulty.

In November, when the first report on the Omicron variant came out of South Africa, scientists could only guess at how it might behave differently from earlier forms of the virus. All they knew was that it had a distinctive and alarming combination of more than 50 genetic mutations.

Previous research had shown that some mutations enabled coronaviruses to grab onto cells more tightly. Others allowed the virus to evade antibodies, which serve as an early line of defence against infection.