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The AstraZeneca Covid-19 vaccine has developed an unfortunate degree of notoriety as supply difficulties and, of late, increased reports of blood-clotting complications post-vaccination have undermined its rollout.
It remains a highly effective vaccine in preventing severe Covid-19 illness and death, though those side effects – and a small number of fatalities – are being linked to the jab.
The latest twist is the European Medicines Agency (EMA) has concluded after extensive evaluation that unusual blood clots in the brain are a very rare side effect of the vaccine, but the health benefits of the protection it provides from Covid-19 greatly outweigh the risks – especially in older people.
Its decision coincided, however, with the UK vaccination advisory body abruptly changing its guidance by recommending healthy adults under 30 should be offered an alternative vaccine to the AstraZeneca jab if there is one available in their area, and they are not at high risk of Covid.
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It has not advised against use of the vaccine for any other age groups.
From an Irish perspective, with the country at the initial stages of its vaccination programme, the associated uncertainty is not helpful, especially when widespread vaccination is the best way to getting closer to normality in the quickest possible time.
What are the latest indications on the clotting problem linked to the AZ jab?
Of 34 million people who had received the vaccine in the UK and the European Economic Area, the EMA has received reports of 169 cases of cerebral venous sinus thrombosis and 53 cases of splanchnic vein thrombosis – both rare kinds of blood clots. Most cases were in women aged under 60, but the current evidence does not suggest age or gender is a risk factor for the side effects, the EMA said. All these cases arose some 14 days after receiving the first dose.
No cases of blood clotting with low platelet levels similar to those in other countries have been reported in Ireland.
The cases, none the less, prompted the EMA to advise that product information on the vaccine be updated to describe the conditions as a very rare side effect of the vaccine, with a warning to be aware of early symptoms including severe persistent headache, blurred vision, and skin bruising beyond the site of injection.
How reliant is Ireland on the AZ vaccine?
The AstraZeneca vaccine is one of four approved for use in Ireland. In the first quarter of 2021, a total of 340,800 doses out of 1.19 million delivered were AZ jabs (29 per cent). For the second quarter it is estimated 813,000 doses will be delivered out of 3.9 million expected by the end of June (21 per cent).
This contrasts with the UK where the vaccine has been the workhorse in its successful vaccination programme. Equally, many countries were banking on it as it is cheap and easier to administer as it can be stored at normal refrigerator temperatures for at least six months.
What are people, particularly women under 60, to make of varying advice?
The risk-benefit profile of the AstraZeneca vaccine is strongly in favour of its use, notably when factoring in high clot risk associated with severe Covid-19 among older people.
That said, there is an inevitable perception issue which requires careful management and balanced public health messaging, especially in relation to younger women.
Germany, France, Belgium and Spain have opted to restrict the vaccine to older groups. Others, such as Norway and the Netherlands, have suspended it entirely. So concerns are understandable.
The latest difficulty has prompted speculation in the US that it won’t need the AZ vaccine because of increased availability of other vaccines – it has yet to approve it for use. All this is an invidious position to be in for what was once called a “game changer” vaccine in the global fight against the virus.
The insidious traits of Covid-19 and emergence of new variants, however, will not allow for choice among the vast majority of recipients – though advice will continue to be evaluated and adjusted, if necessary, based on reported side effects.
Is the Irish advice likely to deviate from the latest EMA position?
This is unlikely as Ireland's regulator, the Health Products Regulatory Authority, together with other EU medicine regulators, was part of the EMA review through membership of its safety committee.
Meanwhile, the National Immunisation Advisory Committee (Niac), which advises on issues related to vaccination, did not change its current advice – issued in mid-March – after the EMA announcement.
That recommended continued use in all age groups though it stressed the need for careful monitoring of side effects. Niac will, none the less, review the latest EMA verdict in detail.
Its response will take in the latest evidence and it will conduct its own risk evaluation. This may result in revised guidance on the AZ vaccine in relation to younger peope – but the overall risk-benefit assessment is still likely to come down in favour of its continued use given the risk of catching Covid-19 is hundreds of times more likely than suffering a blood clot after being vaccinated with the AstraZeneca jab.