Prayer not plague is what changes people’s hearts and a nation’s well-being. So argues John Owen when he writes of the immorality of his nation of England at the time:

It would be an endless work to list all the sins that reign among us—cruelty, violence, uncleanness, sensuality, drunkenness—all raging and reigning to their utmost in the nation. I mention these things as matters that should be  grief to us before God, and should affect us whenever we think of them. To this great predominance and prevalence of sin in the whole nation must be added an awful sense of security.  The truth is that at one time the people of this land were awakened a little.  When God’s judgments were upon us—the plague, the  fire, and, a year later, another warning—there was a degree of quickening like a  man awaking from a dead sleep, lifting his head and rubbing  his eyes for  a few moments. But having observed something of the world now for about forty years, I can testify that I never saw our land in such a complacent security as it is at present. 

(from John Owen, Searching Our Hearts pp.11–12 in the Puritan Paperback Edition by Banner of Truth, Emphasis mine.)

Owen goes on to state that God’s people should be affected by observing such immorality. He quotes Psalm 119:136 which reads as follows:

“My eyes shed streams of tears, because people do not keep your law.”

(Psalm 119:136 ESV)

Notice, “because people do not keep your law!” The Christian should be like Lot in having their souls vexed over the immorality around them in their own nations.  But not only that—also the church!

We would do well, brothers, to consider the state of the church of God in the world and among ourselves, and to consider our own condition. There seems to me, I must confess, to be a great decay in all the churches of Christ in the nation, especially among those of us who have had most peace and prosperity. That which we call zeal for God is almost completely lost among us. Some of us have almost forgotten whether there exists such a thing as the cause of Christ in the world. We, who once cried and prayed about it and had it upon our hearts, have sat down in our narrow compass and almost forgotten that there is such a thing as the interest of Christ in the world, inspiring us to an active zeal for the ordinances of God according to his rule, as God requires of us.

(Ibid., 14.)

The solution according to Owen is simply this:

Let us pray that we may be acted upon by the Spirit of God and enlivened by the grace of God in everything we do. 

May the Lord help us to know the plague of our own hearts, and to be enabled to plead with him for grace and mercy to help us in every time of need.

(Ibid., 15)

So, we learn this, namely that plague, fire, and other warnings can at best awaken people a little, but prayer enabled by God through the hearts of his mournful people, can get the ear of God to act upon us by his Spirit.