BRUSSELS — Bruised by major disruptions in supplies of the AstraZeneca and Johnson & Johnson Covid-19 vaccines, the European Union on Wednesday said that it was putting trust and money into the Pfizer-BioNTech shot to salvage its vaccination rollout and secure doses for the future.
The pivot away from AstraZeneca, once a pillar of the E.U. inoculation program, comes after months of discord over delayed shipments and as the company battles worries over rare potential side effects of its shots.
In announcing the change in strategy, Ursula von der Leyen, the European Commission president, said Pfizer had agreed to an early shipment of doses that she said should likely allow the bloc to reach its goal of inoculating 70 percent of adults by the end of the summer.
That goal was in jeopardy after AstraZeneca failed to deliver on expected doses in the first quarter of the year, then suffered fresh setbacks over potential side effects related to blood clots. The European vaccine campaign was dealt a further blow on Tuesday when Johnson & Johnson said it would delay its own rollout in Europe because of similar concerns and after regulators paused its use in the United States.
There was no indication that the European Union was going to cancel existing orders for dozens of millions of doses from AstraZeneca and Johnson & Johnson, or that European health officials had changed their minds that the benefits of the shots outweighed any risks. But E.U. officials indicated that they would negotiate new deals only with companies that are producing Covid vaccines based on messenger RNA, or mRNA, like Pfizer and Moderna.
“We need to focus now on technologies that have proven their worth: mRNA vaccines are a clear case in point,” Ms. von der Leyen said as she announced that the bloc had begun negotiations with Pfizer for 1.8 billion doses for 2022 and 2023.
The Johnson & Johnson and AstraZeneca vaccines use a harmless virus to deliver a piece of genetic material from the virus that causes Covid, prompting an immune system response to it. The mRNA vaccines, based on a newer technology, also use a piece of genetic material from the coronavirus, but not an entire virus, to provoke the immune response.
The E.U. move is an attempt “get ahead of what they see as a race to lock up mRNA vaccine supplies,” said Thomas J. Bollyky, the director of the global health program at the Council on Foreign Relations. He called it “very much an aggressive attempt to try to head off a repeat” of the supply concerns that have slowed the bloc’s vaccination drive.
The European Union was criticized early on for its slow procurement of doses. And it has fallen further behind the United States and Britain as it suffered blow after blow in its inoculation campaign, first with major supply disruptions from AstraZeneca in late January, and then with the emergence of the potential rare blood disorder that has battered the public’s confidence in vaccines and led to appointment cancellations.
“As we can see with the announcement by Johnson & Johnson yesterday, there are still many factors that can disrupt the planned delivery schedules of vaccines,” Ms. von der Leyen said on Wednesday.
Ms. von der Leyen said the Pfizer doses under negotiation for the next two years would include potential booster shots to extend the immunity of people who have already been inoculated, as well as possible new shots or boosters targeting emerging variants that might prove resilient against existing vaccines.
The AstraZeneca and Johnson & Johnson vaccines performed well in clinical trials, and the possible dangerous side effects have been rare. But trials of the Pfizer and Moderna shots shows that they were even more effective in preventing infection, and similar side effects have not emerged. Another mRNA vaccine, from CureVac, is in clinical trials.
Naor Bar-Zeev, a vaccine expert at the Johns Hopkins Bloomberg School of Public Health, said the E.U. decision reflected difficult trade-offs for a region that has struggled to secure doses quickly. “They were trying to find the least worst call to make here, not the best call,” he said.
On Wednesday, the European Medicines Agency, the bloc’s top drug regulator, said it was expediting its investigation of “very rare cases of unusual blood clots” in recipients of the Johnson & Johnson vaccine, and expected to issue a recommendation next week. While the evaluation is ongoing, the agency reiterated its view that the benefits of the vaccine outweigh the risks.
In a setback for AstraZeneca, Denmark on Wednesday became the first country to permanently stop the administration of the company’s vaccine, saying the potential side effects were significant enough to do so given that it had the pandemic under control and could rely on the Pfizer and Moderna inoculations.
With the fresh commitment by Pfizer to bring forward the delivery of 50 million doses originally slated for the end of the year, the company expects to deliver 250 million doses in total to the bloc by the end of June.
Ms. von der Leyen said more than 100 million people in the European Union had received at least one vaccine dose, and 27 million had received both. The additional Pfizer vaccines, together with 35 million doses expected from Moderna over the next three months, and a more limited use of AstraZeneca doses already in the pipeline, should be enough to get the bloc to the coveted milestone of reaching 255 million people by September, E.U. officials said.
In stark contrast to the criticism of AstraZeneca’s handling of its E.U. dealings, Ms. von der Leyen praised Pfizer effusively, highlighting how important the company’s ability to respond quickly to help the European Union has been.
“I want to thank BioNTech/Pfizer — it has proven to be a reliable partner,” Ms. von der Leyen said. “It has delivered on its commitments, and it is responsive to our needs.”
Addressing another sore point, Ms. von der Leyen said that the future Pfizer doses would be produced in the European Union.
Ample exports from the factories within the bloc to the rest of the world have enabled countries like Mexico and Canada to begin their vaccination campaigns, but those exports have also been identified as one reason there were not enough vaccines to go around in Europe.
The United States and Britain, by contrast, held tight to the vaccines made in their countries, helping speed along their inoculation efforts.
Monika Pronczuk and Rebecca Robbins contributed reporting.