Petra Vlhova was best placed to catch the American but she made a couple of mistakes and didn’t build the sort of lead that would have been required to stop Shiffrin.
However such was the nature of Shiffrin’s performance that it wouldn’t have even mattered.
Shiffrin’s second run put her 2.29 seconds ahead of Vlhova, a staggering margin from the best slalom skier of all time.
'Remarkable!' - Shiffrin storms second run to win again in Killington
“That was crazy, that was really a rough ride. I though I was going to fall at every single gate,” Shiffrin said afterwards.
“I was really, really on the limit but it was fun and this crowd is so amazing and they were taking me down the hill again.”
Shiffrin - I thought I was going to fall at every gate
It is her 42nd slalom victory and her fourth in a row at Killington in front of the American fans.
She also goes to 62 overall World Cup wins, level with Annemarie Moser-Proll but still 20 behind the women’s leader Lindsey Vonn.
Elsewhere Sweden’s Anna Swenn Larsson rounded out the podium whilst Nina Haver-Loeseth continued her hugely encouraging return from injury to finish fifth.
Great Britain’s Alex Tilley couldn’t repeat her giant slalom heroics from Saturday but still managed a respectable 24th place finish.
How do you stop Mikaela Shiffrin? Is it possible? In the slalom it certainly doesn't seem possible.
She may have been beaten by the Italians in the giant slalom on Saturday but in the slalom she is in a league of her own.
What is most astonishing is that it still seems as if Shiffrin is making mistakes. They're not the sort of catastrophic mistakes that will lose her races but she's clearly got another level to hit if she tidies up a few things, which is positively terrifying for everyone else.
On a side note this is Shiffrin's second run without her mum Eileen by her side. Eileen has stepped away to be with the rest of the family more following the death of Shiffrin's grandmother, something she spoke to the New York Times about on Friday.
To maintain her levels during this difficult time speaks volumes of her character.