The country’s national medical academy (Anamem) has also cast doubt on the efficacy of Andry Rajoelina’s touted prevention and remedy.
It said it had the potential to damage people’s health as its “scientific evidence had not been established”.
The plant-based tonic is to be given free of charge to the most vulnerable.
Launched as Covid-Organics, it is produced from the artemisia plant – the source of an ingredient used in a malaria treatment – and other Malagasy plants.
It was being marketed in a bottle and as a herbal tea after being tested on fewer than 20 people over a period of three weeks, the president’s chief of staff Lova Hasinirina Ranoromaro told the BBC.
“Tests have been carried out – two people have now been cured by this treatment,” Mr Rajoelina said at the launch of Covid-Organics at the Malagasy Institute of Applied Research (Imra), which developed the tonic.
“This herbal tea gives results in seven days,” said the 45-year-old president, who also urged people to use it as a preventative measure.
“Schoolchildren should be given this to drink… little by little throughout the day,” he told the diplomats and other dignitaries gathered for the launch.
Dr Charles Andrianjara, Imra’s director general, agreed that Covid-Organics should be used for prevention.
He was more cautious about its use as a cure, but said that clinical observations had shown “a trend towards its effectiveness as a curative remedy”, the AFP news agency quotes him as saying.
The Indian ocean island has so far recorded 121 cases of coronavirus, and no deaths.
In response to the launch of Covid-Organics, the WHO said, in a statement sent to the BBC, that the global organisation did not recommend “self-medication with any medicines… as a prevention or cure for Covid-19”.
It reiterated earlier comments by WHO head Tedros Adhanom Ghebreyesus that there were “no short-cuts” to finding effective mediation to fight coronarvirus.
International trials were under way to find an effective treatment, the WHO added.