WORCESTER, Mass. — They gave away lunch. They gave away grocery gift cards. They gave the experience of getting vaccinated on a train. But it turns out there’s another reason why some vaccine hold-outs finally rolled up their sleeves when the Vax Express pulled into Union Station Thursday.
“We’ve definitely seen lately that people have come in and told us that the variant had been one of the main reasons that they finally decided to get the vaccine,” said Samantha Joseph, the community outreach director for CIC Health, one of the groups partnering with the state to use commuter trains as rolling clinics.
The variant in question was recently renamed Delta but it’s closely associated in many minds with the soaring number of COVID-19 cases and deaths that hit India in recent months. Technically known as B.1.617.2, scientists are now studying Delta to see if it’s more transmissible, if it causes more severe disease and whether it can evade available vaccines.
On the issue of transmission, there seems to be growing support that, like the British variant before it – B.1.1.7, renamed by the World Health Organization as Alpha – Delta does seem to spread more quickly.
“There is definitely, from the epidemiology and the clinical studies, there is a smoking gun for sure,” said Dr. Pei-Yong Shi, a professor and researcher in biochemistry and molecular biology at the University of Texas Medical Branch in Galveston.
In Dr. Shi’s lab, they are trying to determine, using animal models, whether Delta exceeds Alpha in terms of transmission capabilities. But Dr. Shi also said the actual numbers on the ground are important to look at, too.
“It is important to look at the trend or trajectory,” Shi said. “Whether this is in the ramping up mode or stabilized or declining. We just have to look at that very closely.”
At the moment, it appears to be ramping up. The Centers for Disease Control and Prevention reports that, from early to mid-May, market share for the Delta variant in the U.S. more than doubled from 1.2% to 2.7%. That still pales in comparison with the Alpha strain, which dominates U.S. infections.
Despite the tiny proportion of havoc Delta is causing now, Alpha proved that more transmissible variants could exhibit explosive growth. In March, the Alpha variant was found in about 27% of infections sequenced in the U.S. It took just two months to get to 70%.
“It does seem, to my surprise, that Delta has a transmission advantage over Alpha,” said Dr. Jeremy Kamil, an associate professor of microbiology and immunology at Louisiana State University Health Shreveport.
But that’s not all.
“It also seems to have, according to Public Health England, a substantial advantage over Alpha in resisting convalescent or antibody responses that came from earlier variants,” Kamil added.
That raises the troubling possibility that those infected with previous strains of COVID-19, who assume they have natural immunity against another infection, may not actually be protected.
As for Delta producing worse disease than earlier variants, that is less certain.
“I’m not quite sure yet,” Shi said. “To clearly validate that, I think it needs more studies in controlled settings.”
But it is possible, Kamil said.
“The assumption that viruses always evolve to become less pathogenic is not a safe one,” he said.
What’s reassuring is that even if Delta is found to be more pathogenic, it appears those fully vaccinated should have little problem fighting the virus off.
However, one study suggests skipping the second dose of vaccines that require such a regimen would be a big mistake with Delta in the mix. It found single doses of the Pfizer and AstraZeneca vaccines provided just 33% effectiveness against the new variant.
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