The future of AstraZeneca's vaccine rollout hinges on 2 crucial decisions, after a month of suspensions and dose shortages

• The EMA is set to conclude Thursday whether AstraZeneca's COVID-19 vaccine caused blood clots.
• If the vaccine is deemed safe, as expected, up to 18 countries could give it out again.
• Separately, the US awaits the results of a trial that could determine FDA authorization of the shot.

Oxford University and the drug giant AstraZeneca have found themselves at the heart of European political theater over the past few weeks. The groups' COVID-19 vaccine was suspended in more than a dozen European countries after reports of blood clots, including some with "unusual features" such as low platelets, among some immunized people.

Vaccine regulators and the World Health Organization have said the vaccine is safe. But after Denmark suspended the shot on March 11, several countries followed, saying they would wait on the results of an investigation by the European Medicines Agency.

The stakes for the EMA's investigation, expected to conclude on Thursday, are high: A finding that the vaccine is indeed safe, as experts expect, would mean the 18 countries that have suspended the shot could begin administering it again. But if the saga stretches on, it could jeopardize the vaccine rollout in Europe and beyond.

The investigation is set against a backdrop of vaccine shortages in the European Union and mixed messages on AstraZeneca's shot from EU leaders since the start of the year.

In January, AstraZeneca said it would cut its vaccine supply to Europe by 60% in the first quarter, to 31 million doses from 80 million, citing production issues. Italy and France have threatened to sue AstraZeneca, alleging a breach of contract, and Europe has insisted on authorizing any exports of homemade vaccines, including AstraZeneca's, which is made at various sites in Europe.

At the same time, AstraZeneca's vaccine has become the least favored shot in Europe, partly thanks to confusing rulings about its effectiveness, especially in older people.

After erroneous reports in Germany in late January that the shot was only 8% effective among older people, the country did not authorize it for people over 65, citing insufficient evidence in this age group - despite the EMA's ruling that the vaccine was safe and effective. German Chancellor Angela Merkel said at the time that she wouldn't get AstraZeneca's vaccine because she was 66. Germany has since backtracked.

Suspensions of the vaccine in several countries are unlikely to help bolster public confidence in it.

EMA investigation could unlock AstraZeneca vaccine in 18 countries

If the EMA finds that the vaccine does not cause blood clots, the 18 countries that have paused the shot are expected to lift their suspensions, avoiding significant delays to their vaccination programs. French Prime Minister Jean Castex said on Tuesday that he would "very quickly" get AstraZeneca's shot if France lifted its suspension.

Countries beyond Europe, such as Indonesia and the Democratic Republic of Congo, have also paused the shot after the reports from Europe. The EMA's investigation could end those suspensions too.

AstraZeneca's vaccine protects against COVID-19, doesn't require ultra-cold storage temperatures, and is fairly cheap, making it a useful tool in tackling the pandemic, especially in low- and middle-income countries. AstraZeneca said in November that it was planning to manufacture up to 3 billion doses of the vaccine in 2021.

But a different ruling or further delays after the EMA's investigation could mean fewer people get vaccinated in Europe and beyond. The European Commission has already said the suspension could affect the EU's target of vaccinating 70% of adults by September 21, The Telegraph reported.

The US is also awaiting results from AstraZeneca's clinical trial involving more than 30,000 people, expected within weeks. The trial results will be fundamental to the Food and Drug Administration's decision whether AstraZeneca's shot can be rolled out in the US.

The US results are also expected to clear up confusion about the vaccine's efficacy, because the trial's design was less complicated than others that combined multiple studies with variable methodologies. In the US trial, participants all got two full doses of the vaccine - during trials in the UK, some participants were given half-doses, which initially seemed to affect how well the shot worked.

Emer Cooke, the EMA's executive director, said on Tuesday that the agency was "firmly convinced" that the benefits of the shot outweighed any risks, while adding that it was the prerogative of each country to suspend the shot if they wanted.

The EMA would be guided by "science and independence" in its investigation, she said. The results are expected Thursday afternoon - the world awaits its recommendation.