COVID-19 vaccines have prompted the nation’s health agency to withhold the shot’s rollout just days before deployment to the nation’s hardest-hit area.On Friday, Health Canada announced it is holding back the J&J vaccine, a one-shot dose that experts and health officials touted as crucial in stemming the spread of the virus amid a devastating third wave of the pandemic, after it was revealed that parts of the batch were made in the same Baltimore plant where millions of other doses meant for the U.S.