Solidarity II is a global collaboration led by the World Health Organization that promotes the implementation of serological surveys of SARS-CoV-2.  Solidarity II provides a collaborative environment for public health agencies and academic institutions around the world to work together to answer some of the most urgent questions about the COVID-19 pandemic.  Understanding the occurrence of infection with SARS-CoV-2 infection is critical for the world to know how frequently infection occurs among different populations, how many people have had mild or asymptomatically infection, how many people have been infected but may not have been identified by routine disease surveillance, and what proportion of the population may be immune from infection by SARS-CoV-2 in the future.  

A complete understanding of the epidemiology and global risk posed by SARS-CoV-2 requires systematic serologic testing.  Serologic testing detects antibodies in the blood that indicate if a person has already been infected.  By conducting surveys among different populations around the world, we can together understand the extent of the COVID-19 pandemic, which in turn will allow local, national, and international decision-makers to respond collectively to the pandemic.

Unique features of Solidarity II are that it provides a global platform for government and academic collaborators to share cutting-edge scientific advances in the area of serologic surveys; accelerates progress globally towards understanding the COVID-19 pandemic; provides every country access to the tools and procedures needed to conduct their own serologic surveys; and promotes access to scientific discovery for all populations globally.