The Centers for Disease Control & Prevention has confirmed that if any U.S. visa applicant refuses one or more doses of an approved COVID-19 vaccine that is medically appropriate for and available to the applicant, then this will be documented as a refusal to be vaccinated. This would result in the visa applicant being considered to have not completed the vaccine requirements. The result is that the applicant will be inadmissible to the United States.

More information on this can be found on the CDC website. 

In line with CDC guidelines, the U.S. Consulate General in Mumbai has confirmed that visa applicants with medical exams scheduled on or after October 1, 2021, are required to be fully vaccinated against COVID-19. The administered vaccine should be listed for emergency use by the World Health Organization (WHO) or be authorized by the US Food and Drug Administration (FDA). 

It should be noted that the medical examination cannot be completed until the applicant has completed the COVID-19 vaccination series. Applicants who cannot complete vaccination before their appointment should still plan to attend their scheduled visa interview; however, a visa cannot be issued until the medical exam is completed and forwarded to the Consulate.

This information can be found here.