COVID-19 vaccines are developed at an American vaccine development firm on March 20, 2020. (Photo: AFP)

In a small, initial trial on 45 participants, Moderna's experimental vaccine produced coronavirus antibodies – which should help fend off the disease.  In the expanded trial starting Monday, half the 30,000 participants will receive a 100-microgram dose of the vaccine, while the rest will be given a placebo. 

Human trials of Russia’s second potential coronavirus vaccine, developed by the Siberian Vector institute, began on Monday, the TASS news agency cited Russia’s consumer safety watchdog. An early-stage human trial of a separate vaccine, developed by the Gamaleya institute in Moscow, was completed this month with scientists hailing the results and authorities planning to move to mass production in the autumn.

So far, more than 150 types of COVID-19 vaccines have been developed, 12 of which have been put on clinical trials.