Now is not the time to let your guard down.

That’s the message from virologist Dr Cillian De Gascun, who took to Twitter to remind the public that one dose of a vaccine is not enough to consider yourself protected against the new Delta variant of Covid-19.

While the effectiveness of the vaccine is reduced for Delta infections, Dr De Gascun said the protection offered is high after two doses.

“Please remember that you are not fully vaccinated until 2 weeks after your second dose of ChAdOx1 Astra Zeneca vaccine, or 7 days after your second dose of Pfizer/BioNTech vaccine.” said De Gascun, director of the State’s National Virus Reference Laboratory.

“Two doses are required for optimal protection against the Delta variant #VaccinesWork.”

Please remember that you are not fully vaccinated until 2 weeks after your second dose of ChAdOx1 Astra Zeneca vaccine, or 7 days after your second dose of Pfizer/BioNTech vaccine. Two doses are required for optimal protection against the Delta variant #VaccinesWork 14/14

— Cillian De Gascun (@CillianDeGascun) June 29, 2021

Dr De Gascun said a “dramatic” increase in the proportion of Delta in Ireland over the last two weeks “will almost certainly lead to Delta dominance by the middle of July, with a consequent increase in case numbers, hospitalisations, and mortality in the following weeks.”