The first case involved a man, 43, with a history of hyperlipidaemia and obesity.
He received a dose of the vaccine on April 18 and suffered cardiac arrest at home four days later.
The man was rushed to Yan Chai Hospital for treatment and he died later that day.
A Department of Health spokesman said it’s contacting the Hospital Authority to obtain further information about the case.
“So far, there is no clinical evidence to indicate that his death was caused by the vaccine,” the spokesman said.
The second case involved a woman, 66, who received her second dose of the vaccine on April 12. She was found unconscious 10 days later and was certified dead at the scene.
Both cases will be referred to an expert committee for assessment.