SINGAPORE: Three months after Cambodia rolled out COVID-19 vaccines, just 11 percent of its population had received at least one dose, while in far wealthier Japan, it took two weeks longer to reach that level.

However, both countries now boast vaccination rates that are among the best in the world.

They are both Asia-Pacific nations that started their immunization campaigns slowly, but have since overtaken the U.S. and many European countries in vaccinating their public.

Asian nations with high vaccination rates include both developed and developing countries, with some having larger populations and others with smaller, but all have experience with infectious diseases, such as SARS, and with vaccine-procurement programs.

Due to low initial infection rates, most Asian countries began vaccinating their citizens relatively late, as well as suffered from initial supply issues.

Additionally, many of their peoples were initially skeptical about being vaccinated, but soaring death rates in the U.S., the UK and India helped persuade even skeptics to receive shots.

Cambodia was one of the earliest countries in the region to start its vaccination program on 10th February, but it is now 78 percent fully vaccinated, compared to 58 percent in the US. It is also now offering booster shots and looking to vaccinate 3 and 4-year-olds.

Early in the pandemic, many Asian countries imposed strict lockdowns and travel restrictions that prevented major surges. But as vaccines were widely rolled out elsewhere, those low rates gave many people the impression that becoming vaccinated was not urgent.

But cases surged when the highly-contagious delta variant ravaged Asia.

Some countries, such as Malaysia, prioritized the vaccination of even the hardest-to-reach groups.

"We made the vaccine accessible to all, with no questions asked," said Professor Sazaly Abu Bakar, director of the Tropical Infectious Diseases and Research Education Center, as quoted by ABC News.

The country now has 76 percent of its population fully vaccinated.

Currently, a handful of Asia-Pacific countries, including Australia, China, Japan and Bhutan, have vaccinated more than 70 percent of their populations or are close to doing so, while Singapore has fully vaccinated 92 percent of its people.

However, some countries are struggling in their vaccination efforts, such as India, which has fully vaccinated only 29 percent of its population of nearly 1.4 billion.

Indonesia has also struggled due to the challenge of conducting its vaccination campaign across the thousands of islands making up its archipelago.