Does your organization have a COVID-19 immunization policy? Perhaps you do not need one. If everyone who works in the organization is willing to get vaccinated then likely there is no issue.
Where the issue arises is if you have some employees who do not want to be vaccinated. This will create some tension in the workplace. Can you insist all of your employees get vaccinated for COVID-19? Is this policy within the mandate of an employer? What I am hearing is no, you cannot require employees to be vaccinated. You have to accommodate this choice as you accommodate other differences in the workplace. What you can do is require employees who are not vaccinated to wear masks while they are on your premises. This policy will balance the interests of the workers who choose to be immunized with those who do not.
Of course, you may have other considerations, such as union agreements to keep in mind when drafting policy. Also, you should check with your own legal advisors to get the advice which is tailored to your specific situation.