Moderna's vaccine, which can be stored and transported more easily than Pfizer's, is approved in Europe, the US and Canada among others.
Vaccines in Singapore are voluntary and free.
The country's prime minister Lee Hsien Loong was among the early recipients, hoping to boost confidence in vaccines that have stirred rare hesitancy in a country that had largely tamed the virus with strict rules, mask wearing and contact tracing.
The island nation of about 5.7 million people has been reporting very few new local cases over the last few months. Since the start of the outbreak, Singapore recorded a total of more than 59,000 coronavirus cases, most of which occurred in crowded foreign worker dormitories.
Only 29 people have died from the disease in Singapore, according to its health ministry.