A SARS-CoV-2 variant with traits similar to that of the Delta variant might cause a more severe pandemic with more infections and breakthrough infections/reinfections than variants with either trait alone, finds a new study.

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The study, published in the journal Cell, indicated that a variant with enhanced transmissibility alone would likely be more dangerous than a variant that could partially evade the immune system. Yet a variant with both traits could cause more infections, reinfections, and breakthrough infections than a variant with either trait alone.

"Thus far, evidence of immune escape the ability of a variant to evade the immune system and cause reinfections or breakthrough infections has been a red flag," said researcher Mary Bushman from Harvard University. "Our findings say it's maybe more of a yellow flag -- this is not such a big deal on its own. But when it's combined with enhanced transmissibility, then it can be a really big deal," Bushman added.

The traits of the Delta variant include enhanced transmissibility and an ability to infect people who had previous infections/vaccination. The analysis simulated a SARS-CoV-2 pandemic with several different hypothetical variants including combinations of the two traits -- enhanced transmissibility, similar to the Alpha variant; partial immune escape, similar to the Beta variant; enhanced transmissibility with partial immune escape, similar to the Delta variant; and a variant with neither trait.

The analysis also factored in how certain variables, such as masking/physical distancing or vaccinations, would affect the pandemic's trajectory. For each of the scenarios, the team analysed the total number of infections as well as the number/percentage of infections averted by vaccination.