As of April 23, city-sites and some state-sites allow walk-up. See list on on NYC Walk Up Vaccination Locations.
New York has multiple vaccination locations and multiple websites for scheduling an appointment. The New York State Health Department runs one website and its own state vaccination hubs throughout the state & NYC. The NYC Department of Health and Mental Hygiene has a couple of websites (detailed below) and multiple hubs as well. Private pharmacies are also now providing vaccinations. Determine eligibility before scheduling.
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You must book an appointment in order to get vaccinated. Most appointments require the use of a computer and email. Vaccinations occur at three basic types of places, each with their own websites:
There are a few NYC-focused volunteer-run websites and Twitter accounts that will alert you instantaneously when an appointment comes available and include links for you to book directly. I've helped people schedule appointments in seconds by just following these tweets or being on their sites so I recommend doing the same.