The group - which also recently increased profit expectations for 2018 - said trading had been boosted by “extensive publicity” surrounding the launch of the new savoury product at the start of January.
It cheered an “exceptionally strong” start to 2019 as the stir caused by the launch of the snack saw a jump in customer transactions.
The group posted a 9.6% rise in like-for-like sales for the seven weeks to February 16, while total sales lifted 14.1%.
This compares with a 2.9% hike in like-for-like sales a year earlier, when trading was hit by extreme weather.
Greggs said: “The rate of growth has eased slightly in February but the strength of trading is likely to have a material impact on the first-half result for 2019.”
It added: “Overall the board now anticipates that 2019 full-year underlying profit before tax (excluding exceptional charges) is likely to be ahead of its previous expectations.”
January’s news that Greggs was to sell a vegan-friendly sausage roll drew a flurry of responses online, including comments from Good Morning Britain TV host Piers Morgan and comedian Ricky Gervais.
Greggs sells 1.5 million sausage rolls a week but created the new option due to public demand after an online petition by Peta, calling for a vegan version, was signed by more than 20,000 people last year.