During the COVID-19 pandemic, most of the vaccines have been developed by a collaboration of more

than one companies, for example, Pfizer-BioNTech, AstraZeneca & Oxford, etc. For such cases,

1) why is it necessary or even optimal to have more than one companies?

2) What is the type of such collaboration?

3) Where is the boundary of the firms?

4) Is it not considered collusion?

5) Does it hamper or enhance technical and agency efficiencies?