Pfizer and BioNTech have confirmed data related to their coronavirus vaccine was accessed during a cyber-attack targeting the European Medicines Agency.
The EMA earlier confirmed they had been targeted by hackers, and launched a 'full investigation' into what had happened.
The agency is currently deciding whether to approve the Pfizer / BioNTech vaccine, with regulators set to meet to assess it on December 29th 'at the latest'.
In a statement, the two pharmaceutical companies confirmed some documents related to their vaccine candidate had been 'unlawfully accessed' in the EMA cyberattack.
They said: "It is important to note that no BioNTech or Pfizer systems have been breached in connection with this incident and we are unaware that any study participants have been identified through the data being accessed.
"At this time, we await further information about EMA’s investigation and will respond appropriately and in accordance with EU law. EMA has assured us that the cyber attack will have no impact on the timeline for its review."
They add that their focus remains on ensuring the vaccine is brought to people around the world 'as safely and as efficiently as possible'.
The UK became the first country to approve the Pfizer vaccine last week, with a vaccination programme now rolling out.
People at risk of severe allergic reactions have been advised, for now, to avoid the new vaccine.
Investigations are ongoing into two cases in which healthcare workers in the UK with a history of allergies suffered side effects after receiving the jab.
Both are said to be recovering well.
Meanwhile, Canada has become the second country to approve the vaccine for use - with officials saying it meets their "safety, efficacy and quality requirements".
US regulators are expected to decide as early as tomorrow whether to approve the vaccine.