Herd, or collective, immunity has been a permanent reference all along the Covid-19 pandemic, often misunderstood as a technical synonym of "epidemic end" once a threshold value of immunized people is reached. The pandemic development has shown that with current variants transmissibility and current vaccines such critical threshold cannot be reached. An effective collective immunity is however attainable, the stronger the higher the population proportion of vaccinated people. This immunity, a powerful brake on the epidemic progression, depends on the degree of solidarity that society enacts as a whole via containment measures (physical distancing, masks) and vaccination. A clear solidarity deficit is manifest within countries in the form of repeatedly delayed adoption of correct interventions against the epidemic and between countries with the heavy shortage of vaccines in countries with low and middle-low income. The lever of counter epidemic actions by governments and health authorities cannot operate without the support of a fulcrum of civic solidarity: it depends only on citizens, individually and collectively, to build it small stone upon stone.