The 47-year-old had been due to make his debut presenting the ITV daytime show with Rochelle Humes on Tuesday but had to pull out after testing positive for COVID-19.
Kay tweeted while watching Humes co-host the show with Eamonn Holmes: "Missing out on my This Morning debut today cause of COVID. I was up for a bit of fashion and cooking with Rochelle.. Hopefully we’ll go again soon… P.s Feeling ok….(so far!) Really appreciate your well wishes..xxx"
Watch: Vernon Kay earned no money while modelling – he was actually in debt!
It was announced earlier this month that Kay – who took part in I’m A Celebrity... Get Me Out Of Here! last year – would be stepping in to guest host This Morning while regular hosts Phillip Schofield and Holly Willoughby are on their summer break.
Kay was due to host the show for three days, while Alison Hammond was scheduled to join Humes for the other two days.
However, Hammond has also been absent due to feeling "unwell". She joked on Instagram that she was still recovering after having a great time partying at Manchester Pride over the weekend.
Kay – who is married to Strictly Come Dancing host Tess Daly, 52 – first entered the spotlight when he was spotted by a model scout at the BBC’s Clothes Show Live and went on to win "Model of the Week" on Channel 4 show The Big Breakfast.
He began his presenting career at the age of 26 on weekend and school holiday morning show T4 in 2000, alongside June Sarpong.
The Bolton-born celebrity went on to host game show All Star Family Fortunes from 2006 to 2015.
Earlier this year he presented ITV's Game of Talents earlier alongside wife Daly.
The couple – who have two daughters, Phoebe, 16, and Amber, 12 – renewed their vows in 2015 in a surprise ceremony in France, organised by Kay.
The two TV stars worked to save their marriage after Kay confessed in 2010 to sending inappropriate messages to glamour model Rhian Sugden and four other women.
Watch: Vernon Kay discusses how he saved an ITV producer from drowning...