ROME/BRUSSELS, Oct 29 (Reuters) - Leaders of the world"s 20 largest economies are set to commit to supporting efforts to shorten to 100 days the period needed to develop new vaccines, drugs and tests in a pandemic, according to a draft joint document. In normal circumstances developing vaccines takes more than a decade, but the COVID-19 pandemic spurred an unprecedented rush in research, trials and regulatory procedures that made it possible to have vaccines ready in less than a year.ROME/BRUSSELS, Oct 29 (Reuters) - Leaders of the world"s 20 largest economies are set to commit to supporting efforts to shorten to 100 days the period needed to develop new vaccines, drugs and tests in a pandemic, according to a draft joint document. In normal circumstances developing vaccines takes more than a decade, but the COVID-19 pandemic spurred an unprecedented rush in research, trials and regulatory procedures that made it possible to have vaccines ready in less than a year.