It is important not to overstate the impact of the latest recommendation for the AstraZeneca vaccine on the national immunisation campaign.

To use a musical analogy, the chords may have changed but the song remains the same.

It will now be about re-jigging the existing vaccine dose quantities expected, to meet the changed age profiles. While it is more complex, it can be managed.

The campaign will have the same number of vaccines, that has not changed. But the latest development may result in a short pause in the programme, while it readjusts to reflect the changed recommendations.

The reliance on AstraZeneca may lessen over time but it will still be needed to vaccinate people between 60 and 69 years and there is a significant number of people in that group yet to be immunised.

Indeed, there is the possibility that this tighter age group will get vaccinated faster now, with over 800,000 AstraZeneca doses due between now and June.

Most people who have already received one dose of the AstraZeneca vaccine, will get their second shot as usual.

Also, the bonus for people who will now get the Pfizer vaccine instead is that they will be fully vaccinated faster, as the gap between the first and second dose is shorter with Pfizer (28 days) than with AstraZeneca (12-week gap).

The HSE is now assessing the impact of the National Immunisation Advisory Committee (NIAC) recommendation that the AstraZeneca vaccine only be used for people over 60 years.

Most people who have already received one dose of the AstraZeneca vaccine, will get their second shot as usual, even if they are under 60 years.

Deputy Chief Medical Officer Dr Ronan Glynn has said he hopes the change will not be too disruptive and that it will not result in prolonging restrictions.

NIAC says that the risks of severe Covid-19 decrease in younger people. That is the rationale for the decision.

The changes are complex and some people will be understandably confused about what it all means for them. The cancellation of AstraZeneca vaccination clinics today will also have caused some anxiety, although the HSE says these will be rescheduled. It will have affected many thousands of people.

The Irish College of General Practitioners said today that GPs will be facing an extra workload and calls from patients today, anxious about the changes. People are being asked to be patient while the impact is being assessed.

Health authorities have stressed that all of the vaccines authorised here are effective.

The age cut-off for the AstraZeneca vaccine has been introduced because the benefits versus the risks of the vaccine may vary with age.

The very rare side effects of the AstraZeneca vaccine are of high consequence and increase as you go down in age groups. In contrast, NIAC says that the risks of severe Covid-19 decrease in younger people. That is the rationale for the decision, based on an abundance of caution.

Under the vaccination programme, people are not given a choice of vaccine. They are being urged to accept the brand they are offered.

Latest developments are another bump on the road but they should not throw the plans off course to a significant degree.

The changes will have to be fully explained to and absorbed by the public.

The HSE will also have the task of explaining precisely how it will affect the national vaccination programme.

Politically, the Government will want to ensure there is no change to the target to have over 80% of the adult population vaccinated by June and everyone fully vaccinated by September.

The nature of the pandemic and the new vaccines to deal with Covid-19 means that twists and turns can be expected. More vaccines will be coming on stream soon.

If there had been only one vaccine available, NIAC would not have recommended this change with AstraZeneca because it says the benefits hugely outweigh the risks.

The latest developments are another bump on the road but they should not throw the plans off course to a significant degree.