(CNN) Bhutan has fully vaccinated 90% of its eligible adult population in a week with Covid-19 shots, a feat that has been described as a "success story" and a "beacon of hope" for other countries in the region, the UN Children's Fund (UNICEF) said Tuesday.
The tiny South Asian kingdom of 770,00 people is nestled in high in the Himalayas between India and China, and its high altitude, remote mountain villages, nomadic herders and extreme weather posed unique challenges to health workers delivering the vaccines safely across the country.
The rollout campaign of second doses, which began on July 20, involved months of preparation that included setting up cold chain storage facilities in difficult to reach health clinics, deploying a helicopter to deliver vaccines to the more remote locations, and an army of volunteers distributing the vaccines along mountain footpaths.
By Tuesday, about 480,000 people had been vaccinated out of an eligible population of 530,000 people, UNICEF's Bhutan representative Will Parks said from the capital Thimphu, adding that it was "arguably the fastest vaccination campaign to be executed during a pandemic."
Bhutan administered around 500,000 AstraZeneca vaccines, donated from India, during its first vaccine campaign in March and April. But when India halted vaccine exports due to a devastating Covid wave spurred by the Delta variant, Bhutan began searching elsewhere for donations.
Several governments answered the call. Bhutan secured 500,000 Moderna shots from the United States through the global COVAX vaccine sharing program. Denmark donated 250,000 doses of AstraZeneca and China had previously donated 50,000 doses of Sinopharm. More than 100,000 doses of AstraZeneca from Croatia, Bulgaria and several other countries were due to arrive on Tuesday.
The international donations have been hailed as an example of countries pulling together to direct surplus vaccines where they are needed most.
"When we see countries rally around each other, when we see hands come from multiple governments to support those countries that urgently need vaccines because they just don't have enough, that's really heartening to see," said Parks.
"It tells the story of global solidarity at a time when that hasn't been evident for the last year or so. Now we are seeing that solidarity, that multilateralism come about again. And its so important at a time when the world is in crisis."
UNICEF, which is on the ground helping with Covid logistics, the delivery of vaccines, cold chain equipment, as well as planning and training, said Bhutan's success highlighted the importance of countries that have vaccine surplus to donate to countries in need.
All Bhutan citizens over the age of 18 were eligible for the vaccine, with authorities offering a choice between the Moderna and AstraZeneca shots. In addition, more than 2,000 children aged 12-17 in two districts in lockdown on the border with India, were inoculated during the latest round using Pfizer vaccine that was brought in a few months back, Parks said.
The government has also bought 200,000 doses of Pfizer vaccine, which is set to arrive later this year, and is expected to be used to vaccinate children.
But ensuring the vaccines were distributed safely to the population was a logistical feat involving more than 2,400 health workers and 22,000 volunteers, who went door to door engaging the community on the vaccines and Covid response.
To deliver the shots, volunteers had to pick up the vaccines from helicopters and walk across difficult terrain to remote vaccine centers, all while ensuring the shots remained safely stored at the correct temperatures.
Flying the vaccines in to Bhutan from around the world also posed challenges.
The charter flight of half a million Moderna shots was flown by an Indonesian air crew out of Kentucky. But Bhutan's only international airport Paro has one of the world's most dangerous approaches and involves a steep bank through Himalayan peaks onto a short runway. Less than 20 pilots are certified to make the landing.
"We had to send a Bhutanese pilot to Calcutta to meet that flight and he navigated that flight into Paro," said Parks.
In recent years, Bhutan has made great strides in reducing poverty, declining from 36% in 2007 to 12% in 2017, according to the World Bank. While most of the population work in agriculture, with much of its rural population relying on subsistence farming, development has grown. Hydropower, for example, has become a major source of growth for the country and helped finance social services such as education, electricity and piped water.
The country is probably best known for its 'Gross National Happiness' index, which is used to measure living standards, development, education and governance.
But the kingdom has been one of the most successful at combating Covid, thanks to early planning and a quick response that involved closing its borders, mass testing, contact tracing and social distancing, as well as strict lockdown and quarantine measures. With just over 300 doctors before the pandemic, Bhutan trained thousands of health workers and implemented a national Covid response plan.
There have been a total of 2,489 reported Covid cases and just two deaths -- the first was reported in January this year.
Health experts said strong leadership bolstered the public health response and outreach to the community. Three top government leaders -- the prime minister health minister and foreign minister -- are doctors or public health experts.
Prime Minister Lotay Tshering was an early advocate of the vaccines and frequently posts video messages on social media answering questions from the public and explaining the vaccine and Covid response.
King Jigme Khesar Namgyel Wangchuck has also played an active role throughout the pandemic. The 41-year-old monarch traveled across the country trekking to villages and communities to raise awareness of the vaccines.
The Buddhist nation, also called the Land of the Thunder Dragon, became a constitutional monarchy in 2008 after the king abdicated and relinquished his powers to his son, setting the nation on the path to democracy.
Bhutan's vaccine rollout makes it a stand out among its South Asian neighbors, such as Bangladesh and India, which are struggling to combat deadly outbreaks of the Delta variant and ramp up their vaccine rates.