Hanoi, June 27 : Vietnam has reported the highest-ever spike in the number of single-day Covid-19 cases, majority of them detected in Ho Chi Minh City, since the onset of the pandemic in the country early last year, according to the Health Ministry. There were 738 new cases registered on Saturday, of which 727 were locally transmitted and 11 were imported, Xinhua news agency quoted the Ministry as saying. The new cases increased the country's overall infection tally to 15,275. Among the domestic cases, 621 were detected in Ho Chi Minh City, 16 in Bac Giang province, and 11 in Hung Yen province, the Ministry said. Most of these cases were contacts of previously confirmed cases or linked to community clusters. Nationwide 6,137 infected patients have so far recovered, while nearly 175,700 people are being quarantined and monitored. The country's overall coronavirus death toll stood at 74. Vietnam plans to trial its vaccine passport program from July in the northern province of Quang Ninh, under which travellers who have been fully vaccinated or have recovered from Covid-19 and tested negative upon arrival, will be quarantined for only seven days instead of 21, local media reported. /IANS