Health trusts across England were sent details of an IT security patch that would have protected them from the crippling ransomware attack, NHS Digital said.
Large swathes of the NHS have been paralysed by the cyber attack, which hit 200,000 victims in 150 countries around the world.
But NHS Digital said it had made health trusts aware last month of IT protection that could have prevented the attack.
The governments of the world should treat the cyber attack as a "wake-up call", the president of Microsoft has said.
In a blog post Brad Smith wrote that after a vulnerability was identified a security update was released for newer Windows systems, but "many remained unpatched globally".
Mr Smith continued that engineers had been "working around the clock" to try and help all Micorsoft customers affected by the attack and that "broader and important lessons" should be learnt from the "WannaCrypt" malware.
He continued that users must ensure they update their computer's security systems regularly.
Mr Smith stressed that governments must report vulnerabilities in their computer systems to the companies they have bought them from.
He finished by saying: "We should take from this recent attack a renewed determination for more urgent collective action.
"We need the tech sector, customers, and governments to work together to protect against cybersecurity attacks.
"More action is needed, and it’s needed now.
"In this sense, the WannaCrypt attack is a wake-up call for all of us."
Hospitals have stopped diverting patients following last week's cyber attack which crippled many NHS Trusts' IT systems.
A young computer expert from north Devon who was hailed a hero for helping to stop the global cyber attack said he was just "doing my bit".
One surgery has no access to medical records.