Indonesia is among the Southeast Asian nations most heavily stricken by the Covid-19 pandemic, and the ASEAN country that conducts the most comprehensive vaccine cooperation with China. Still, it has tried to diversify its vaccine supply to avoid being over-reliant on China's vaccine. Unsurprisingly, China’s vaccine diplomacy in Southeast Asia carries an expectation that recipient countries should be more accommodating on the South China Sea issue. Will Indonesia's resolve to stand firm on ASEAN’s position on the South China Sea waver?