Centers for Disease Control and Prevention (CDC) Director Robert Redfield has given the green light to Pfizer’s mRNA Covid-19 vaccine, officially allowing for it to begin being administered in the United States. 

“Last night, I was proud to sign the Advisory Committee on Immunization Practices’ recommendation to use Pfizer’s COVID-19 vaccine in people 16 and older,” Redfield said in a statement.

Tens of thousands of vials of the vaccine had begun being transported earlier this morning from a facility in Michigan to regions across the United States, as health officials begin implementing the largest vaccination effort in US history.

Despite being rivals, shipping giants UPS and Fedex are working collaboratively to get the vaccines distributed as widely across the US as they could manage in as short a time period as possible. The companies have been outfitting trucks and planes with dry ice and other cooling features to keep the vaccines at the supercool temperatures they need to be kept at to remain viable.

The first shots are expected to be given tomorrow, while in New Jersey the first vaccinations will be given to health care workers on Tuesday.