You could try two approaches. One would be to use a plugin called denoiser by MagicBullet, which you have to buy. It does a terrific job but is painfully slow.
The second approach would be to export your sequence to a full resolution TIF sequence. Then use Photoshop's Image Processor, to batch the files-> running an action you create to apply the effect Despeckle.
You can try to export just a single frame, take it into Photoshop, and play with the Despeckle / Noise Reduction filters you have under the Noise drop down under effects, until you get the desired results. Then record the action of the final settings you feel look best.
Run Image Processor on your exported TIF sequence, saving back to TIF at same resolution, and have Image Processor run the action you recorded applying the filter settings you deemed best.
Judging by the image you provided, I would try Despeckle first, then add perhaps a very very small gaussian blur (very small like 0.1 or 0.2), then last, ADD noise to the image, use a very low variable, like 2 or 3, and use monochromatic noise (no color). Adding noise, a very small amount, will add a bit of texture to the image, much like film grain, and help mask out any little specks which might have been missed by the previous effects.
Again: Despeckle -> Gaussian Blur 0.2ish -> Add Noise No Color Checked setting in the 2-4 range (setting may need to be higher if your image size is large, say 4k).
Record that, then process.
Take your TIF sequence processed through photoshop. Drag into PremierePro. Set Still frame length to 1 Frame.
Create new sequence from 1 of the frames to match frame settings. Drage all your images to sequence. Render out as whatever you want. Then take back into AE if need be.