KALAMAZOO, Mich. (NewsNation Now) — President Joe Biden toured a state-of-the-art coronavirus vaccine plant Friday as extreme winter weather across broad swaths of the U.S. handed his vaccination campaign its first major setback, delaying shipment of about 6 million doses.

The disruptions caused by frigid temperatures, snow and ice left the White House and states scrambling to make up lost ground as three days’ worth of vaccine shipments were temporarily delayed. The president’s trip to see Pfizer’s largest plant had been pushed back a day due to a storm affecting the nation’s capital.

At the Michigan plant, Biden walked through an area called the “freezer farm,” which houses some 350 ultra-cold freezers, each capable of storing 360,000 doses of the Pfizer-BioNtech vaccine. Double-masked, the president stopped to talk with some of the workers, but it was difficult for reporters on the trip to hear what was said.

“All of you here are doing some of the most important work in this facility, right here, that can be done,” Biden said in an address to plant workers.

“Take the vaccine when it’s your turn and available. That’s how to beat this pandemic,” he said.

Speaking after Biden’s visit, Pfizer CEO Albert Bourla said on Friday that the drugmaker expects to be able to double the weekly number of doses of its COVID-19 vaccine it will supply to the United States in the next few weeks.

“We have improved our processes to double the batch size and increase yield and we have deployed more efficient lab test methods to reduce release times,” Bourla said in his remarks.

Earlier in the day, White House coronavirus response adviser Andy Slavitt said the federal government, states and local vaccinators are going to have to redouble efforts to catch up after the interruptions. The setback comes just as the vaccination campaign seemed to be on the verge of hitting its stride. All the backlogged doses should be delivered in the next several days, Slavitt said, still confident that the pace of vaccinations will recover.

Slavitt said about 1.4 million doses were being shipped Friday as the work of clearing the backlog begins.

Biden announced last week that the U.S. will have enough supply of the coronavirus vaccine by the end of the summer to inoculate 300 million people and remains focused for now on making sure every American is inoculated, administration officials say.

The government is going ahead with plans to open five new mass vaccination centers, one in Philadelphia, and four others in the Florida cities of Miami, Orlando, Tampa and Jacksonville.

Pfizer has said it will provide the U.S. government with 100 million doses by the end of March and another 100 million by the end of May. It has promised the full 300 million doses by the end of July.

Last year, President Biden announced a vaccination goal of 100 million coronavirus shots in his first 100 days in office.

New figures from the White House show the steady increase in the pace of vaccinations over President Joe Biden’s first month in office.

Much of the increase, according to data from the Centers for Disease Control and Prevention, comes from people receiving their second dose of the approved vaccines from Moderna and Pfizer.

Biden is on track to beat his goal of 100 million injections in his first 100 days in office — though the pace must pick up even further to meet his plans to vaccinate nearly all adults by the end of the summer.

More than 73 million vaccine doses have been distributed across the United States, with more than 57.7 million doses administered, according to the CDC.

There has been nearly 28 million confirmed coronavirus cases in the United States and more than 493,000 Americans have died from the virus, according to data complied by Johns Hopkins University.