On Saturday, Johns Hopkins University reported more than 4.6 million cases in the US and a death toll surpassing 154,000.
The government was slow to decentralize testing sites, preventing private companies and states from providing their own testing.
In response to the health secretary's claims, a think tank, Mexicans Against Corruption and Impunity (MACCIH), started an investigation into the number of death certificates versus the number of reported deaths from coronavirus.
Until now, Vietnam had been relatively spared amid the pandemic, compared with some of its neighbors, with the total number of confirmed cases standing at just 509 as of Friday morning, according to the Vietnam News Agency.
Since first appearing in China last December, the novel coronavirus has spread to at least 188 countries and regions.
Coronavirus cases around the world have reached almost 17.7 million with nearly 700,000 deaths. A third person died there of coronavirus complications, officials said Saturday, a day after it recorded its first-ever death as it wrestles with a renewed outbreak after 99 days with no local cases. "Then I'll put on a mask and I'll stop talking", he said.
In South Korea, prosecutors arrested the elderly leader of a secretive religious sect linked to more than 5,200 of the country's approximately 14,300 confirmed cases.
Japan's capital Tokyo saw its third day straight of record case numbers on Saturday, according to the metropolitan government.
Latin America is now one of the pandemic's global hotspots.
The World Health Organization (WHO) has warned the effects of the pandemic will be felt "for decades to come".