Exteriors of Pfizer’s vaccines factory in Belgium

Drugmaker Pfizer on Wednesday resumed deliveries of its coronavirus vaccine doses from its Belgium manufacturing plant in Puurs.

Police were present as the lorry carrying supplies left the factory.

Pfizer has said it's been ramping up production and expects to be able to make 2 billion doses in 2021, up from its earlier forecast of 1.3 billion doses.

Many public health officials have expressed skepticism that the Pfizer vaccine could be successfully kept so cold across the globe.

Pfizer has been shipping the shots in special containers with dry ice, but even in the US, some doses have been thrown out because they weren't kept at the proper temperature.

Pfizer and BioNTech said they would also help health systems handle the vaccine, which requires ultracold storage.