While all Christians should frequently attend the Lord's Table in the manner which Scripture prescribes, 1 Cor. 11, 26-29, we cannot speak of an absolute necessity of the Lord's Supper. The spiritual eating of Christ's body, John 6, 53, or faith in Christ (sola fide), is indeed absolutely necessary for salvation; but the sacramental eating of His body is not absolutely necessary. Also here the words of St. Augstine apply: "Not the privation, but the contempt of the Sacrament condemns" (Contemptus sacramenti damnat, non privatio).
However, let the Christian minister conscientiously remind his parishioners that indifference to, or neglect of, Communion implies contempt of the Sacrament and that contempt for the Lord's institutions is tantamount to apostasy. (Cp. Luther, Large Catechism, "The Sacrament of the Altar," 42 ff.: "Such people as deprive themselves of, and withdraw from, the Sacrament so long a time are not to be considered Christians.")