Prof. Carlos A. Guzmán's department is researching a vaccine against SARS-CoV-2 that can be administered via the mucous membranes, thereby conferring superior protection against virus infection and transmission. Instead of being injected into the upper arm, the vaccine could be administered by nasal spray. An adjuvant developed at the HZI is used in this project. The adjuvant c-di-AMP enhances the immune system's reaction to the vaccine.
The distinction between a variant and a strain hinges on whether the virus in question behaves in a distinct way, according to Dr. Adam Lauring, who studies the evolution of RNA viruses at the University of Michigan, and Emma Hodcroft, an expert on viral phylogenetics at the University of Bern in Switzerland.
“Genomes that differ in sequence are often called variants,” Lauring and Hodcroft explained in the Journal of the American Medical Assn. “Strictly speaking, a variant is a strain when it has a demonstrably different phenotype.”
In other words, a particular coronavirus specimen may contain one or more mutations that another specimen lacks. If there is no detectable functional difference, it is merely a variant.
However, if those mutations make the specimen more transmissible than its predecessors, or endow it with an added ability to evade a drug or vaccine, or alters it in another meaningful way, then it qualifies as a distinct strain.
The two terms have been thrown around interchangeably, especially by those who have become armchair virologists over the course of the pandemic. But they are not synonymous.
“The distinctions are important,” Lauring and Hodcroft wrote.
By these measures, the virus from South Africa qualifies as a strain because its response — or lack thereof — to COVID-19 vaccines sets it apart from other versions of SARS-CoV-2. Its behavior is so singular that vaccine researchers are designing booster shots to target it.
The coronavirus from the U.K. counts as a strain as well because it spreads more readily than other variants. Indeed, researchers at the U.S. Centers for Disease Control and Prevention have forecast that the U.K. virus is spreading so fast that it’s on track to become America’s “predominant variant in March.”
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