Here's every website you can use to book a vaccine appointment in California You will likely need to spend some time online to find an open slot. FacebookTwitterEmail Hundreds wait in queue for the Janssen COVID-19 vaccine (Johnson & Johnson) in Oakland, Calif. Beginning April 15, anyone 16 or older will be eligible for the vaccine in California.SOPA Images/LightRocket via Getty Have you discovered a great source for finding vaccine appointments? Email agraff@sfgate.com. California will open up vaccine eligibility to individuals 16 and over on Thursday, and a rush of millions of residents will be jumping online to find vaccine appointments.