Vertex displacement on sphere break the mesh

I'm trying to make a simple noise effect on a sphere with shaders. I tried to use ashima's perlin noise but the effect wasn't what I expected so I create my own shader based on Phong.

Here is what I get with this code in my vertex shader:

attribute int index;
uniform float time;

vec3 newPosition = position + normal * vec3(sin((time * 0.001) * float(index)) * 0.05);

gl_Position = projectionMatrix * modelViewMatrix * vec4(newPosition, 1.0);

where index is the index of the vertex and time the current elapsed time.

The noise effect is exactly what I expected but the sphere mesh is open...

How can I keep this effect and keep the sphere mesh closed?

Most likely your sphere contains duplicated vertices. Get rid of them and your shader will works well. Or get rid of your shader dependency on "index".