WASHINGTON (BLOOMBERG) - The storms that blanketed much of the US in snow and ice paralysed the Covid-19 vaccination campaign just as it had finally quickened, with communities unclear when the next doses will arrive and appointments cancelled by the thousands.

In Chicago, all testing and vaccination sites were shut and health officials said they expected delays in vaccine shipments for a few days. Power outages created a temporary crisis in Houston when a backup generator failed and threatened to spoil more than 8,000 doses of the Moderna vaccine.

Rice University and other Houston institutions used the vaccines to inoculate students to prevent the drug from going to waste. The storm's effects even cascaded into parts of the country where few flakes fell at all.

The vaccine delays are a setback for a nation that had been delivering about 1.7 million doses into patients arms' daily, twice the pace of a month ago, according to the Bloomberg Vaccine Tracker. Now, clinics that reopen will have to reschedule thousands of appointments for patients without bumping those already in line and some fear clinics will shut out of fear of snow.

"I don't think we should take days off because of the weather," said Amesh Adalja, a senior scholar at the Johns Hopkins University Centre for Health Security who studies pandemic preparedness.

The cold weather that has gripped the central US has covered almost three-quarters of the US with snow, to an average depth of 6 inches (15cm). Winter storm warnings and weather advisories earlier this week stretched from New Mexico to Maine and affected 157 million people. Electric grids across the South went down, leaving thousands without power.

Shivering shippers

The poor weather was expected to hamper air hubs for FedEx in Memphis, Tennessee, and United Parcel Service in Louisville, Kentucky, both major players in transporting the vaccines.

FedEx said it wasn't aware of any spoilage within its transportation network. While the severe weather is limiting its ability to pick up and deliver in some cities, vaccine deliveries are getting priority status, said spokeswoman Bonny Harrison on Tuesday.

Accounts from state officials, health authorities and shippers suggest the storm will slow the pandemic recovery by at least a few days. At the current pace, it will still take about eight months to cover three-quarters of the US population.

More than 80 Indiana vaccine clinics closed Tuesday. In Alabama, 38 county health departments closed Tuesday due to the weather, while others had already shut Monday. Some slots will be made up for on Saturday, and some counties are pushing back second doses by two weeks.

Cascading delays

The effects of the storm spread even into areas that avoided the worst weather.

In relatively balmy Florida, the chaos elsewhere delayed the delivery of some 200,000 doses of the Moderna vaccine. Publix Super Markets, which has become a go-to vaccine provider for many Floridians, was forced to abandon plans to schedule thousands of additional seniors for shots on Wednesday.

Likewise, Colorado's allocation of 133,000 vaccines that were expected to arrive today through Thursday were held up by bad weather in Tennessee.

Illinois officials warned that weather likely will mean fewer vaccinations over the coming days, according to an emailed statement from the state health department. Illinois administered 40,354 doses Monday, down from a seven-day rolling average of 63,772.

In snow-covered Texas, parts of which were colder than Alaska, the US Centres for Disease Control and Prevention and its shipping partners had already postponed vaccine shipments on Friday. The state won't get a new supply of vaccines until Wednesday at the earliest, although deliveries to local communities could be delayed still further, said Lara Anton of the Texas Department of State Health Services.

"No one wants to put vaccine at risk by attempting to deliver it in dangerous conditions," she said by email. "Local providers have postponed vaccine clinics because it is not safe for people to be out across much of Texas."

Fortunate owls

Some lucky students at Houston's Rice University got an impromptu dose Monday, likely months before they ordinarily would have done so, given their age.

When a back-up generator at a county health unit failed amid massive statewide outages, officials rushed to find anyone willing to take the doses before they went bad.

Nearby Rice accommodated the request, finding a dozen people qualified to administer shots and sending out email and text message blasts across the campus. A student newspaper pitched in by sending messages on social media.

All told, the university was able to give 800 shots to students and essential workers in about five hours, said Kevin Kirby, a vice-president for administration at Rice. Some recipients waited a couple of hours in frigid weather until the university was able to move them inside a gymnasium, spaced apart and wearing masks.

"We had huge lines within the first 30 minutes," Kirby said.