There is no evidence that consuming bananas prevents COVID-19.
Back in March, a spokesperson for the president of the Philippines said that eating bananas can prevent COVID-19. This statement was repeatedly debunked, including by Maria Rosario Vergeire, Department of Health Undersecretary in the Philippines, who confirmed that there was no evidence that eating bananas prevent the transmission of COVID-19.
The COVID-19 pandemic has given rise to a lot of potentially dangerous misinformation. For reliable advice on COVID-19 including symptoms, prevention and available treatment, please refer to the World Health Organisation or your national healthcare authority.