More than 350 Indonesian healthcare workers who were vaccinated with China's Sinovac vaccine caught COVID-19, , Reuters reported.
While the majority of those who tested positive for the coronavirus were asymptomatic, dozens needed hospital care.
Badai Ismoyo, head of the health office in the district of Kudus in Central Java, told the outlet that more than 90% of the facility's beds are occupied. He added that 5,000 healthcare workers were currently dealing with the outbreak, about 7% of whom have become infected.
It's likely that the outbreak is fueled by the more transmissible Delta variant, which originated in India. The number of workers testing positive has prompted officials to question how effective the Sinovac vaccine is against variants.
The Delta variant can also result in more serious illness. It may also be able to evade protection from existing vaccines, as Insider's Aria Bendix reported.
"The data shows they have the Delta variant (in Kudus) so it is no surprise that the breakthrough infection is higher than before, because, as we know, the majority of healthcare workers in Indonesia got Sinovac, and we still don't know yet how effective it is in the real world against the Delta variant," Dicky Budiman, an epidemiologist at Australia's Griffith University told Reuters.
The statistic came after 128,000 healthcare workers who were vaccinated were monitored between January and March and it was found that 94% of them hadn't caught symptomatic COVID-19.
The efficacy rate from trials in Brazil was lower than that found by Indonesian officials, at 50.7% effective against symptomatic COVID-19.
The study and trial did not look at the Delta variant.
Indonesia recorded over 1.9 million infections with 53,000 deaths since the start of the pandemic. Doctors and nurses accounted for close to 950 deaths. They were the first to receive the Sinovac vaccine in January.