The tweet, posted by Professor Steve Hanke at the John Hopkins University (JHU) on June 10, named Vietnam among a list of countries that supposedly "do not report Covid-19 data or are reporting highly suspicious data," referring to them as the "rotten apples of coronavirus data."

A chart was posted along with the tweet, citing data from statistics website Worldometer and saying Vietnam had no reported Covid-19 data, while India, Venezuela, Egypt, Syria, Yemen, Turkey and China were "reporting highly suspect data."

The statement quickly garnered attention online, receiving around 3,800 retweets and 1,700 replies in more than a week. Many have expressed disagreement over Hanke’s statement, saying Vietnam did in fact report zero deaths from Covid-19, while questioning Hanke’s method of data collection.

"Vietnam is being praised all over for its superb handling of the crisis and here it is – no data reported? How’s this possible?" asked a Twitter account holder named Chetan Bhardwaj.

Another member of the public eventually sent an email to Hanke asking for clarification, to which the response was because Worldometer had no death data for Vietnam, Hanke thought there were no such info available.

An online open letter by public health researchers, professionals and concerned citizens to the JHU soon followed, demanding Hanke to retract his statement and correct the info.

The letter was sent to JHU on Wednesday, a source, who is among the first to write the letter and wishes to remain anonymous for privacy reasons, said.

As of Wednesday, the letter had been signed by 285 people, online publishing platform Medium reported.

"We, as part of the audience, became very concerned since Covid-19 data for Vietnam was clearly available on worldometers.info (the same website Professor Hanke cited) at the same time of his tweet... It initially seemed Professor Hanke mistook Vietnam’s widely verified zero deaths from Covid-19 as no reported data," the letter read.

"This error, however, has remained despite repeated attempts by public health practitioners and the public to alert him to the fact," it added, accusing the errors and excuses in Hanke’s statements as "highly unscientific" and "representing low professional standards."

"We suspect Professor Hanke’s claim in the ‘rotten apples’ chart was more politically driven than evidence based. Professor Hanke’s action likely bears several serious consequences," it said, adding the statements could spread misinformation to the public and undermine JHU’s reputation.

The letter concluded by requesting Hanke to "publicly retract the "rotten apples" chart and issue a statement with correct information about Vietnam via the same channel(s) he published the chart, and for the JHU to "issue public statements with correct information about Vietnam to prevent further misinformation."

On June 16, Hanke posted another tweet regarding the matter, saying "Contrary to an image I posted last week, Vietnam turns out to have a ‘perfect’ record in its fight against the novel coronavirus. Official Vietnamese data indicate the country has not suffered any related fatalities – zero deaths."

He has not retracted the previous tweet.

Vietnam has confirmed 335 Covid-19 cases so far, with only 10 active infections left. The Health Ministry releases updates on Covid-19 cases twice a day.

The country has reported no community transmission in over two months.