Among many interesting observations of this article, which cites a great many studies, is that while reception on the tongue does not appear to be more dangerous than reception in the hand, reception kneeling is clearly preferable to reception standing. We reproduce a key passage below; the whole article can be read here (or download the pdf here).
The Holy Species used in the Latin Rite is nearly dry and therefore is likely to have low adhesion of outside particles, further reducing the infectious risk. While receiving the Holy Bread, the communicant normally extends the tongue forward, requiring to hold breath for a while. This reduces possible respiratory output. The traditional manner of receiving Communion on the tongue is therefore unlikely to incur a high risk of infection transmission.
Traditional reverent practice of the Catholic Church incorporates additional elements making it even less risky in the current COVID-19 pandemic. The kneeling position of the faithful while receiving the Host would provide spatial distancing about 50 cm (Fig. 1a): the communicant’s face is located at the level of the chest of the Eucharistic Minister. Provided the communicant stays silent, uses nasal breathing, and the duration of the interaction is short (very few seconds), this would not incur a high risk to the Eucharistic Minister (usually the priest whose safety is prioritized, see above). Furthermore, reduced verbal response of the communicant directs the droplets and aerosol towards the chest of the Minister, which is by far a lower risk than in the face.