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According to this document dated December 29, 2022 from the Indian Ministry of Health and Family Welfare (MoHFW), vaccination is preferred, but not required for US citizens.
https://www.mohfw.gov.in/pdf/GuidelinesforInternationalArrivals29thDecember2022.pdf
It does appear that you may be subject to screenings for symptoms and testing, especially if symptomatic, but there is not a vaccine requirement to enter unless you are entering from one of the "high risk" countries. (Currently China, Singapore, Hong Kong, Republic of Korea, Thailand, and Japan)
If the above document is updated in the future, a new version will be posted under resources>travel advisories on this page.