Vaccination commenced in Britain and Northern Ireland.
The Covid-19 vaccination programme has received an early setback in the UK.
Regulators there have said people with significant allergies not to take the Covid-19 vaccine after two health workers who were given Pfizer/BioNtech Covid jab suffered allergic reactions.
The Medicines and Healthcare Products Regulatory Agency (MHRA) advised that: "Any person with a history of a significant allergic reaction to a vaccine, medicine or food (such as the previous history of anaphylactoid reaction or those who have been advised to carry an adrenaline autoinjector) should not receive the Pfizer/BioNtech vaccine.
"Resuscitation facilities should be available at all times for all vaccinations. Vaccination should only be carried out in facilities where resuscitation measures are available".
It is reported that the NHS staff involved had significant histories of allergic reactions and needed EpiPen or similar device.
They developed symptoms of "anaphylactoid reaction" shortly after being vaccinated.
The UK authorities, which are the first in the world to approve the vaccine, say the issue did not emerge in the clinical trials process. The MHRA fast-tracked vaccination.
Ireland's rollout of vaccination will not commence until the European Medicines Agency approves the vaccines. It is currently examining data around the use of the vaccine being administered in Britain.
The Irish Government has ordered 2.3 million doses of the Pfizer vaccine. More than 7.5 million vaccines made by four firms have been placed by Irish authorities.