The 18-year-old only made his first Premier League start in November 2012, but he is now a serious contender to make it into Hodgson's World Cup squad.
"It's a very proud day for me, I still cannot believe it," Shaw told Southampton's website.
"I'm only 18. I cannot believe it. I am really excited. It's a massive confidence boost for me.
"Roy rang me this morning and told me I was in the senior team, and that I was there on merit.
"I wasn't expecting it. I didn't know what to say."
A picture of Shaw rubbing his eyes while talking on his phone, captured shortly after he heard he had been called up to the squad, showed just how much the news meant to the teenager.
Shaw came through the famed Southampton youth academy before he was fast-tracked into the first team by former manager Nigel Adkins.
His form this season has led to speculation that he could be called up to the senior squad, but he says he was only expecting to be included in the Under-21 squad for next week.
"I saw (speculation about a senior call-up) on Twitter over the past month but I tried to ignore it," the 18-year-old said.
"I was always thinking I was going to be called up to the Under-21 squad but to get a senior one is unbelievable."
With Ashley Cole now out of the Chelsea team, Shaw stands a reasonable chance of being included alongside Everton left-back Leighton Baines in Hodgson's 23-man World Cup squad.
But when asked whether thoughts of playing in Brazil this summer had crossed his mind, Shaw said: "No, nothing.
"There is a friendly and hopefully I will get some game time and keep up the performances I have been having at Southampton and then who knows what will happen."
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