Add another obstacle to the already stuttering rollout of COVID-19 vaccines — brutal winter weather creating dangerous conditions and forcing tens of thousands of would-be shot takers to wait longer.

Icy roads from the West Coast through the Midwest and into the South shut down vaccinations at many sites, pushing those with appointments back into the pool of those waiting. The schedule disarray could get worse, with nasty weather expected to last for several days. Places from Oregon to Oklahoma could see a foot of new snow by the weekend.

Limited vaccine supply, varying state plans and other points of confusion have slowed the effort to get doses to Americans. Statistics from the U.S. Centers for Disease Control and Prevention on Thursday showed a little over 10% of the country — 34.7 million people — have received at least one dose, and 11.2 million have received both of the two doses required for both the Pfizer and Moderna vaccines.

With the elderly now the focus of mass vaccinations, state and local health officials decided the risk of falls or accidents outweighed the benefit of a timely shot.

“Unfortunately, if you look at the weather for next week, it’s not going to be easy,” Oklahoma Deputy Health Commissioner Keith Reed said. “It’s just another challenge with this vaccine program. You talk about all the logistical challenges, and now Mother Nature wants to make it a little bit more of a challenge for us.”

Ice-covered roads led to crashes and road closures in Oklahoma. A mass vaccination site in Tulsa was shut down, forcing 2,000 appointments to be rescheduled. At another site in Oklahoma City, 700 appointments were moved to March 10.

The prospect of an extended delay was worrisome for those who have received their first shot. The second shot for the Pfizer vaccine is recommended 21 days after the first, and the second dose of the Moderna vaccine is recommended 28 days later.

Dr. Dale Bratzler, Oklahoma University Health’s chief quality officer, said a later-than-ideal second shot will still be an effective booster, whenever you can get it, though within six weeks of the first shot is best.

“If you don’t get it within the 21 or 28 days, that’s OK,” Bratzler said. “Just go ahead and get it as soon as you can.”

In Texas, where at least six people were killed Thursday in a massive pileup on an icy interstate, Dallas’ largest vaccination site was ordered shut down after consultation with the National Weather Service, said Dallas County Judge Clay Jenkins, the county’s top administrator.

More than 42,000 people have received the first dose in downtown’s Fair Park, which the Biden administration announced Wednesday would soon become one of three federal mass vaccination sites in Texas capable of delivering 10,000 shots a day. The dangerous weather conditions also come ahead of a long weekend for many because of President’s Day, which state health officials warned could push back the arrival of vaccines even more.

“We have two potential events that may delay shipments next week,” said Imelda Garcia, chairwoman of the state’s vaccine allocation panel.

In Missouri, wind chills in the single digits was a big factor in postponing mass vaccination drive-throughs being operated by the National Guard.

“The National Guard tells us it’s very difficult to thaw frozen vaccine at an outdoor event when the temperature may be 5 degrees,” said Robert Knodell, deputy chief of staff for Gov. Mike Parson. He said most of the postponed events will be moved back only a few days, depending on when the weather breaks.

A forecast of up to 14 inches of snow in parts of Oregon was enough to cancel a drive-through vaccination clinic at Portland International Airport for up to 4,500 people age 80 and older.

“Our goal is to keep our patients, members and volunteers safe by mitigating the risk of driving/commuting in the snow and exposure to freezing temperatures,” the Oregon Health & Science University said in a statement.

(AP)