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The US has a few options. Two of them are mRNA and Novavax. The latter is a previously preferred choice by the then Chief Scientist. It is like a slice of the inactivated virus. However, the process is taking a long time. The US is also aware of the mRNA failure. It is faster to develop and distribute.

They got vector J&J as well.
Novavax adhere grown spike proteins to a protein body.

All vaccine will have more or less affected by variant 
as inactivated vaccine is using whole piece, it yield more consistent results.
Others fluctuate wider range.

So far manufacturers look more on high efficacy so as to get authority approval, than making it safer.