A row has broken out between EU member states over coronavirus vaccine allocation in the latest fallout from AstraZeneca’s worsening supply shortfalls to the bloc.

Leaders of a group of European states wrote to the presidents of the European Council and European Commission complaining of “huge disparities” in the allocations of vaccines between member states. The letter, which was signed by Austria, Bulgaria, Croatia, the Czech Republic, Latvia and Slovenia, calls for a debate at leaders’ level.

However, other member states countered that the six member states are complaining about the adverse results of their own procurement decisions. The commission defended the system, saying the allocation of doses had followed a “transparent process”.

The EU is grappling with the consequences of a fresh round of shortfalls in AstraZeneca deliveries as it struggles to get its vaccination drive on track. The British-Swedish company has confirmed to member states that it will only deliver 30m doses in the first quarter of the year, less than the 40m figure expected. That number was itself a big cut from the 100m or more shots the EU had originally expected by the end of March. 

The company says it is now planning to deliver only 70m doses in the second quarter of the year, instead of 180m. This is in part because it has not been able to source supply from outside the EU because of restrictions on exports being operated around the world. 

The delivery shortfalls have once again focused attention on the systems under which vaccines are shared out between member states under the auspices of the EU’s vaccine procurement strategy. The current dispute is coalescing around the distribution of an accelerated delivery of 4m BioNTech/Pfizer doses, diplomats said, as member states scramble to get vaccines as quickly as possible. 

While all EU countries have the right to pro-rata population-based shares of every vaccine bought by the European Commission, they can opt to buy more or less of each jab as they wish. Any unused shares can then be purchased by other member states.

A number of countries decided earlier in the process to weight their portfolios towards the AstraZeneca jab and buy less of the BioNTech/Pfizer and Moderna products, the first two to receive EU regulatory approval. They are now lagging on deliveries because of AstraZeneca’s production problems.

Their original reasons for going long on AstraZeneca include that the company had a big international supply network and its vaccine seemed likely to come to market quickly, said one diplomat from a country that bet on the jab. Other attractions are that the Oxford/AstraZeneca vaccine is much cheaper than the other two and does not require the ultra-low temperature storage they do.

“At the time of contracting they seemed to be the fastest in development and [to have] the biggest capacity,” the diplomat said of AstraZeneca.

But the consequence of AstraZeneca’s supply problems is that those countries have received fewer vaccines to date proportionally than member states weighted towards the Pfizer and Moderna drugs.

In their letter, the six countries complained that deliveries of vaccine “are not being implemented on an equal basis following the pro rata population key,” adding: “If this system were to carry on, it would continue creating and exacerbating huge disparities among Member States by this summer, whereby some would be able to reach herd immunity in a few weeks while others would lag far behind.”

Sebastian Kurz, the Austrian chancellor and one of the signatories, tweeted that if the current distribution continues “it would result in significant unequal treatment — which we must prevent.”

However, the commission said it was the member states themselves that had agreed to allow departures from the pro rata of population allocation system that Brussels favours. “It would be up to the Member States to find an agreement if they wished to return to the pro rata basis,” it said.

There is “full transparency between Member States as to who gets what” on vaccines, since the allocations are decided by a procurement steering board on which they all sit, an EU official stressed.

Countries that went heavy on Pfizer rather than AstraZeneca and are enjoying the benefits in the form of more timely deliveries are likely to look askance at efforts to reshuffle the distribution key.

“Some countries did not buy all they could. They chose another strategy betting on other vaccines that was cheaper and easier to transport to be available for them,” said one EU diplomat. “It is not fair nor has it anything to do with solidarity to change the allocation system as has been agreed. It would not be fair to those who for months have enforced strong measures and lockdown.”

The question of vaccine strategy is set to be debated at an upcoming EU summit on 25 and 26 March.