ANCHORAGE, Alaska (AP) — The usual transportation difficulties in rural Alaska have presented unique obstacles for the distribution of COVID-19 vaccines, officials said.

Dozens of remote villages lack hospitals and road connections, while ultracold freezers required for storage of specific varieties of the vaccine are essentially nonexistent, Alaska Public Media reported.

Tribal health care providers responded by mobilizing a massive effort delivering thousands of doses to remote areas.

Providers airlifted vaccine to villages using a fleet of chartered planes, while the medicine also was delivered over choppy seas on a water taxi.

Some clinicians were shuttled around villages on sleds pulled behind snowmachines. The effort was reminiscent of the so-called Serum Run that delivered diphtheria treatment to Nome a century earlier.

"We have these deep stories of Alaska adventure that are related to public health," said Tom Hennessy, a University of Alaska Anchorage infectious disease epidemiologist. "And here's another one playing out right before our eyes."

Dr. Ellen Hodges encountered the unforeseen difficulty of Alaska being too cold in some places to vaccinate frontline health care workers.

"It became immediately apparent that the vaccine was going to freeze in the metal part of the needle," said Hodges, who contended with sub-zero temperatures on a remote Southwest Alaska airport tarmac.

Hodges kept doses tucked in her shirt until they were injected.

"Once we got that sorted out, it was pretty great," Hodges said. "A lot of us felt the importance of it — of making sure we could get our health aides protected against this horrible, unpredictable disease."

Curt Jackson used his aluminum landing craft to ferry nurses and a load of vaccine to the village of Seldovia through heavy seas in Kachemak Bay.

"It was definitely kind of creeping along on eggshells as we're slamming through these waves, trying to be as careful as possible, knowing there's this super special cargo on board," Jackson said. "I'm not going to lie — I got choked up realizing this was like this first little step towards victory."