The most recent measurement of radiation reduction was made at the company Verkotan in Finland. Below you can see an excerpt from the compilation which shows that the radiation from the mobile decreases by 90.7-98.9% at the various measuring points around the phone when the mobile cover is on. The so-called SAR value (SAR = Specific Absorption Rate) was also reduced by up to 95%. All investigations have been monitored and evaluated under the guidance of an independent professor - Olle Johansson, previously active at Karolinska Institutet and Kungl. Institute of Technology.
In this video you can see him tell more