You also want to add the maximum scale
<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1">
UPDATED
I agree with some of the comments, the declaration should not limit the scaling by the user as this is bad practice. The below is a better approach and I believe that the zooming bug has long since been fixed by Apple.
<meta name="viewport" content="width=device-width, initial-scale=1">