Аннотация:The properties of QED-vacuum polarization, caused by the supercritical external Coulomb source with charge $Z$ and size $R$, are explored in an essentially nonperturbative approach with emphasis on the vacuum energy $\cal{E}_{VP}$ (where VP stands for vacuum polarization.) It is shown that in the supercritical region $\cal{E}_{VP}$ turns out to be a decreasing function of the Coulomb charge, resulting in decay into the negative range as $∼−Z^4/R$. Moreover, it is indeed the decline of $\cal{E}_{VP}$, which provides the required energy for (presumably possible) positron emission. Found this way, properties of the resonance decay are in agreement with those achieved by other methods. The additional problems of spontaneous emission, caused by lepton number, are also discussed.