I prefer not to drink the wine from the challis because I am concerned with spreading germs. Is it necessary to drink the wine in order to fully participate in Mass and communion?
No, it is not necessary. It is not necessary because the fullness of Christ’s body, blood, soul and divinity are fully contained in both the host and the species of wine.
Council of Trent:
This holy council instructed by the Holy Ghost, who is the spirit of wisdom and understanding, the spirit of counsel and godliness, and following the judgment and custom of the Church, declares and teaches that laymen and clerics when not offering the sacrifice are bound by no divine precept to receive the sacrament of the Eucharist under both forms, and that there can be no doubt at all, that communion under either form is sufficient for them to salvation. For though Christ the Lord at the last supper instituted and delivered to the Apostles this venerable sacrament under the forms of bread and wine, yet that institution and administration do not signify that all the faithful are by an enactment of the Lord to receive under both forms.