It's important to note that the AstraZeneca vaccine is adenovirus based [0], not mRNA based like the Pfizer and Moderna candidates. It was to be expected that this approach could cause more complications. mRNA vaccines have their own issues, but they do not involve live viruses being injected [1]. Instead they use lipid nanoparticles as a substrate to enter the body's cells [2].
[0] https://www.astrazeneca.com/media-centre/press-releases/2020...
[1] https://www.phgfoundation.org/briefing/rna-vaccines
[2] https://www.nature.com/articles/s41586-020-2639-4