Yes... but a strange study:- More than 6,600 medical personnel...

Yes... but a strange study:
- More than 6,600 medical personnel were recruited
- The nasal spray was given to about half the participants
- Only ran for 1 month (ran from October 31 to November 30). This seems quite short...
- about half the drug group dropped out during the observation period
- Around 5,000 of the participants made it through the study

50% of 3300 who got the "drug". about 50% of "drug group dropped out (approx 1650).
6600 - 1650 = 4950.
And about 5000 completed the study... so maths seems to say: only about 50 dropped out of the control group and 1650 out of the drug group?

I realise these numbers are "approx" and are reported in a news article, which may have made mistakes, but something seems a bit off to me.