The latest Covid-19 outbreak in Taiwan is a lesson that a containment strategy aiming for zero local transmission may not be sustainable in the long term, a public health professor said Tuesday.

Before the recent explosion in cases, Taiwan had reported very few Covid infections for more than a year — and most were imported. That allowed daily activities to continue largely as normal and won the island international praise for its containment measures.

But that left Taiwan “completely susceptible” to new variants of the coronavirus that are more transmissible and potentially more severe, said Benjamin Cowling, professor and head of the epidemiology and biostatistics division at The University of Hong Kong’s School of Public Health.

“Probably less than 1% of their population have had natural infection and therefore natural immunity, and … less than 1% have been vaccinated — so they’re almost completely susceptible,” Cowling told CNBC’s “Squawk Box Asia.”

Taiwan, with a population of roughly 24 million, has reported more than 8,500 confirmed Covid cases and 124 deaths as of Monday, official data showed.

Cowling said Taiwan will find it difficult to control the latest outbreak. Authorities may need stricter social distancing measures given that testing capacity hasn’t ramped up enough and the island’s vaccination progress has been slow, he added.

“It’s a warning to other parts of Asia that are also trying this elimination strategy, it’s not necessarily sustainable in the long term,” said the professor.

Asian economies have generally shown a lower tolerance for Covid infections compared to its peers in other regions.

Governments in Hong Kong and Singapore, for example, have been quick to tighten measures to stem out small upticks in cases. Meanwhile, countries such as the U.S. and U.K. are still reporting thousands of daily cases, but quicker vaccination has allowed the countries to roll back restrictions.

Like many of its regional peers in Asia, Taiwan has faced challenges securing Covid vaccines, said Cowling. Part of Taiwan’s hurdle is politics, said the professor.

Taiwanese President Tsai Ing-wen said in a Facebook post last week that the government has purchased vaccines developed by AstraZeneca and Moderna. She accused China of blocking a deal with Germany’s BioNTech, which has co-developed a vaccine with U.S. pharmaceutical Pfizer.

Beijing has denied Tsai’s accusation.

China claims Taiwan as a runaway province that must one day be reunited with the mainland — using force if necessary. The Chinese Communist Party has never governed Taiwan, which is a democratic self-ruled island.

“There’s a lot of politics involved in getting vaccines to Taiwan,” said Cowling. “I think they’ll be able to do it, but they won’t be able to vaccinate enough people right now to stop the current outbreak, they need to use social distancing, lockdowns to deal with this.”