The Government will continue to observe and monitor people who were vaccinated to look out for those with side effects, collect this data and refine the criteria for vaccination.

Health Minister Gan Kim Yong said this yesterday when asked about the 72-year-old man who suffered cardiac arrest on Tuesday night after getting his first dose of the Pfizer vaccine in the morning.

The patient, who was admitted to the intensive care unit at Tan Tock Seng Hospital (TTSH), has a medical history of cancer, hypertension and hyperlipidaemia.

Mr Gan reiterated TTSH's initial assessment that there was no indication the patient's cardiac arrest was due to the vaccination.

"I want to assure Singaporeans that we will continue to monitor data not only locally, but also internationally, so that it is a continuous process that will refine our processes, refine our criteria to ensure that it is safe," he said at the Jalan Besar Community Centre.

People getting vaccinated have to go through a thorough questionnaire to ensure that they do not have a contraindication.

A contraindication is anything, such as a medical condition or symptom, that is a reason for a person to not receive a particular treatment.

After the vaccination, everyone will be observed for 30 minutes.

At the end of the half-hour period, those vaccinated will go through another round of questions to ensure that they are well.

The medical team present will also give the patients advice, should they have any adverse reaction, on where to get help.

"So, I want to assure Singaporeans that we do take this very seriously," Mr Gan said.

"Whether (these incidents) are related to vaccination or not, we want to know if there are any such incidents so that we can investigate in-depth and better understand the situation."