General exemptions for COVID vaccination will apply in countries where the vaccine is not routinely available or where the vaccine is not age appropriate. The Department of State encourages all immigrant visa applicants to get vaccinated against covid-19 as soon as possible so as not to experience delays in processing their visa.
The CDC announcement can be found at the following link: https://www.cdc.gov/immigrantrefugeehealth/panel-physicians/covid-19-technical-instructions.html.