Should AstraZeneca shot still be playing role in Irish vaccine rollout?

For the 29th time the HSE is tweaking the Covid-19 vaccine rollout following the latest advice that the interval between AstraZeneca doses should be reduced from 12 weeks to eight.

The recommendation from the National Immunisation Advisory Committee (Niac) once again shines a spotlight on AstraZeneca, the vaccine with the most "issues" among the four authorised products in Ireland.

AstraZeneca was one of the first vaccines out of the traps late last year, but since then it has been dogged by concerns over its effectiveness, safety and supply. Despite playing a lead role in the UK's swift and largely successful vaccine drive, this vaccine is getting the cold shoulder from the EU, where Pfizer has been the main workhorse of an accelerating immunisation programme.

In Ireland about 550,000 AstraZeneca doses had been administered up to May 11th, when HSE records stopped due to the cyberattack on its system. Almost half a million people, a mix of healthcare workers, vulnerable patients and 50s- and 60s-somethings, still have to get a second dose.

Holohan and Donnelly to meet Limerick TDs over rise in Covid-19 cases

---

Niac continues to advise against mixing Covid-19 vaccines

---

Government should set end date on emergency powers, says human rights report

---

Nine-month post-Covid immunity ‘increases fully vaccinated numbers with single dose’

---

Many of these people may now receive their second dose four weeks earlier as a result of the latest Niac recommendation. But only if there are sufficient supplies to allow for this to happen; deliveries of AstraZeneca have been repeatedly subject to delays and changes, mostly due to manufacturing process issues.

But should AstraZeneca be continuing to play any role in our vaccine rollout given the concerns that have arisen over its safety and effectiveness?

Despite accounting for only one in four doses administered, AstraZeneca is the subject of more reports of suspected side effects than Pfizer and Moderna together, according to the Health Products Regulatory Authority (HPRA).

Most of these are minor in nature, but the HPRA has received 41 reports of blood clotting linked to AstraZeneca, and a handful (less than five) of the very rare but serious clotting events combined with low platelet counts.

UK data

A broader picture can be garnered from UK data, with the latest Public Health England update detailing 348 reports of serious blood clots with low platelet counts. These reports occurred in 189 women and 156 men ranging in age from 18 to 93 years; there were 61 deaths, a fatality rate of 18 per cent.

The incidence after one dose was 13.6 reports per million doses, but this dropped to 1.3 per million doses after two doses.

So if serious clotting, though rare, affects all age groups why is Ireland operating an age threshold (officially 50, but in practice, 60) for administering the vaccine?

This point has been made forcefully by Trinity College Dublin immunologist Prof Kingston Mills, who has questioned the advisability of continuing to use AstraZeneca.

We are in a good phase of the pandemic, with cases stable and immunisation proceeding well. The main worry comes from more transmissible variants, principally the delta variant (Indian) that has gained a foothold in parts of London and northern England.

UK studies have shown the AstraZeneca and Pfizer vaccines are only 33 per cent effective in protecting against infection by the delta variant. This rises to 88 per cent after two doses for Pfizer, but only 60 per cent for AstraZeneca.

This means that thousands of Irish people in their 50s and 60s who are waiting months for a second AstraZeneca dose are seriously exposed to infection by the delta variant (though this remains very rare here), even as younger people at less age-related risk benefit from quicker immunisation using the other vaccines available.

Alternatives

Prof Mills has suggested we mix vaccines by given people who got a first dose of AstraZeneca one of the alternatives as a second dose. At least five EU states are doing this, according to the European Centre for Disease Control.

Extra supplies of Pfizer or Moderna would have to be procured to allow this to happen, but in any case Niac has decided against this approach, at least until stronger evidence emerges that it works.

Notwithstanding the issues raised, all the vaccines currently available appear to provide excellent protection against serious illness or death from Covid-19, which is what counts most. AstraZeneca has performed better in real-world conditions in the UK than it did in clinical trials.

The commonly repeated advice to “take the first vaccine you are offered” remains true, though it should be tweaked to “take the first full vaccine course you are offered”.