Because it's mostly not like you can throw a folder with a "recipe" over a fence and just have someone manufacture a vaccine in the required amounts and quality.
The closest ones to this are probably vector vaccines like the AZ one, because they use a "relatively" well-known delivery technique (as in: one that was at least already used for a single market-ready vaccine before the Covid-19 ones). For that reason, AZ has several production partnerships around the world already, for example with the Serum Institute of India, and the AZ vaccine is considered the likely "workhorse" for global immunization because of this relative ease of manufacturing (and storage, of course).
But it quickly gets harder with the mRNA vaccines. While those are also produced in production partnerships and subcontractor scenarios, the original producer appears to be much more intertwined with its subcontractors, performing some steps by themselves and outsourcing other steps. mRNA vaccine mass production technology is relatively proprietary and new, even newer than the already-pretty-new vector vaccine stuff, and the entire mass production scale-up has only been done very recently under massive time pressure for these Covid-19 vaccines. This basically dictates that with these outsourcing initiatives, the original producer cannot simply hand over some instructions and wait for finished vaccines to appear at the loading bay of a subcontractor, but has to transfer significant amounts of very specialized know-how to the subcontractors, which makes such operations very personnel-intensive and hard to scale.
> The closest ones to this are probably vector vaccines like the AZ one, because they use a "relatively" well-known delivery technique (as in: one that was at least already used for a single market-ready vaccine before the Covid-19 ones). For that reason, AZ has several production partnerships around the world already, for example with the Serum Institute of India, and the AZ vaccine is considered the likely "workhorse" for global immunization because of this relative ease of manufacturing (and storage, of course).
AFAIK the Serum Institute wasn't manufacturing any vector based vaccines prior to the Oxford/AZ vaccine, despite being the largest vaccine manufacturer in the world. They put in $100 Million of their own money to adapt to the AZ pipeline & scale it up.
The closest ones to this are probably vector vaccines like the AZ one, because they use a "relatively" well-known delivery technique (as in: one that was at least already used for a single market-ready vaccine before the Covid-19 ones). For that reason, AZ has several production partnerships around the world already, for example with the Serum Institute of India, and the AZ vaccine is considered the likely "workhorse" for global immunization because of this relative ease of manufacturing (and storage, of course).
But it quickly gets harder with the mRNA vaccines. While those are also produced in production partnerships and subcontractor scenarios, the original producer appears to be much more intertwined with its subcontractors, performing some steps by themselves and outsourcing other steps. mRNA vaccine mass production technology is relatively proprietary and new, even newer than the already-pretty-new vector vaccine stuff, and the entire mass production scale-up has only been done very recently under massive time pressure for these Covid-19 vaccines. This basically dictates that with these outsourcing initiatives, the original producer cannot simply hand over some instructions and wait for finished vaccines to appear at the loading bay of a subcontractor, but has to transfer significant amounts of very specialized know-how to the subcontractors, which makes such operations very personnel-intensive and hard to scale.
Two highly recommended links that provide very informative details about mRNA manufacturing hurdles in particular are these: https://blogs.sciencemag.org/pipeline/archives/2021/02/02/my... https://blog.jonasneubert.com/2021/01/10/exploring-the-suppl...