This change in vaccine validity was first announced by the government in November.
Approximately 260,000 people have been vaccinated with the J&J vaccine in Austria since the start of the vaccination campaign.
Of those, around 75,000 have not received a booster.
The Austrian government has for some time recommended people who received the J&J vaccine – along with those who were vaccinated with Astra Zeneca – to get an mRNA vaccine (either Moderna or Pfizer/Biontech) as a booster.
Anyone who has received the Johnson and Johnson jab is recommended to get a booster shot 28 days afterwards.
The reason for the policy change is a belief that the J&J jab has a lower effectiveness against the Omicron variant, the government confirmed on Wednesday.
“The requirement for a second vaccination with Janssen in order to receive a valid vaccination certificate is based on the latest scientific data that are available to us in Austria” the government said on Wednesday.
“In the case of a Janssen vaccination, a refresher of the vaccination protection seems to be necessary – especially in view of the Omikron variant.
“Therefore, we call on all people who have been vaccinated once with Janssen to be vaccinated again for their own protection.”