Using would denotes a certainty that the vaccines will be available for this time scales However from the context I would seriously doubt this definition. (see reference below).
The use of “WILL” again denotes certainty. However "Will" is most often used to discuss things or situations that may take a long time to happen. "Going to" is used instead of will for events that are going to happen in the near future.(see reference below).
A. "With India administering 30_40 lakh doses daily, this suggests that existing stocks are going to be available for 10_13 days, though there is a considerable variation within the states in the number of doses being made available".
A . *"With India administering 30_40 lakh doses daily, this suggests that existing stocks could be available for 10_13 days, though there is a considerable variation within the states in the number of doses being made available"
I believe both are better answers. Although, because of context, I would use could.
The use of will relates to a more distant (future) action or occurrence so I would not use will in this instance.
Ref Expressing a Future Action: When To Use “Will” And “Going To”.
Will can be a present tense verb that means to cause something to happen through force of desire. It can also be a modal auxiliary verb in various tenses.
USE WILL FOR A FAR FURTHER FUTURE ACTION One important detail about “WILL” is that it is most often used to discuss things or situations that may take a long time to happen.
WHEN TO USE “GOING TO” One huge difference in using GOING TO versus WILL, is that you use GOING TO when the action was already decided on even before speaking of it.
'will' and 'would' Ref
would is the past tense form of will which denotes both ability and certainty. In this scenario we are talking about a future event, we have no need to be polite in this context. It is however "hypothetical" so it would be grammatically correct to use "would".
However, because the situation in debate is a possibility as opposed to a certainty and it is not a conditional hypothesis. it therefore leads me to conclude could is a more appropriate word.
[Ref] Because it is a past tense, would it is used:
to talk about the past
to talk about hypotheses (when we imagine something)
Is it could or would?
Both could and would are verbs that have many senses.
Could is a conditional verb that expresses possibility.
Would is a conditional verb that expresses certainty, intent, or both.
Ref writing explained