Last month I was exposed to a number of life-threatening diseases. My body came into direct contact with Typhoid, Hepatitis A and B, and Tetanus. Yet, this exposure was carefully initiated for my health, not my harm.

This dangerous encounter occurred during immunisation in preparation for a short fact-finding mission to rural Fiji in preparation for next year's Year 13 Gospel Gap Year trip. To prevent my body from falling ill to a number of tropical diseases, my doctor gave me a tiny dose of the bacteria so that should I be normally exposed, my immune system would be ready to recognise the disease and prepared to fight it. The tiny dose was too small to harm, but large enough to educate.

Immunisation is great when the disease is life-threatening. But immunisation can be an issue when the foreign object is life-saving.

This kind of problem can occur when we give people a tiny taste of the gospel without a full exposure to the implications or fruit of the message. If we are not careful, we can lead people to end up hardened against Jesus, not softened to his promises.

The writer to the Hebrews made reference to this very kind of problem when he said that "It is impossible for those who have once been enlightened, who have tasted the heavenly gift, who have shared in the Holy Spirit, who have tasted the goodness of the word of God and the powers of the coming age, if they fall away, to be brought back to repentance" " (Hebrews 6:4-6a).

There are two ways in which we might end up immunising people against the gospel.

The first can happen when we give people a tiny portion of the gospel that fails to represent the whole. An example of this is when we tell people that becoming a Christian will guarantee health, wealth and happiness in this life. When the troubles of this life show the foolishness of that claim, those who believed it will be tempted to reject the whole gospel, and never to believe it again at a later date. The little bit of half-truth has immunised them against Jesus.

The second can happen when we present the gospel in a way that is inconsistent with the broader context of the organisation. It may be that a school presents the gospel to the students during chapel, but the overall ethos is no different to any other secular institution. The students hear the gospel, but the overall message is that Jesus can be "bolted-on' to life with little effect. Students are brought up thinking they have "done' Christianity, but they have received such a little dose of the gospel that it has had no effect upon them other than to immunise them against it for the rest of their life.

This risk of evangel-immunisation presents a real challenge to us in our ministry at the local church and also in our Christian schools.

In our local churches we need to be ready to show that following Jesus is costly. In our increasingly affluent and "prosperous' nation we should expect many rich young rulers to reject Jesus because of the high cost of following him (cf. Luke 18:18-30).

In our Christian schools we need to teach and discipline in a way that is consistent with the gospel we proclaim in chapel and Christian Studies classes. We want to make sure that students are fully aware of the cost of following Jesus, and that they are not Christians simply by virtue of enrolment in the church school. And we must pray for us and them that through our ministry to them they will have a full encounter with the true Jesus as they meet him in his word by his Spirit.

It is sad to encounter people who have rejected Jesus and his gospel because the small taste they experienced has immunised them against him. Some may say, "I tried Christianity, but it failed to live up to its promises of prosperity, so in the future I'm going to try a different belief". Others may say, "I got exposed to Christianity at school, but it didn't seem to really have an impact on me, so I'm going to try something different".

There are no easy answers to this problem. But in our attempts to win over our world we must not sell Jesus short. We should continually pray that God would give us the strength to represent him honestly and truthfully, and that his Spirit would use our words to breathe life into our hearers.

We should always expect people to reject Jesus and his gospel. However, it is vital that as we preach him to our world that they get to meet the true Jesus, not some sort of three-wish genie or religious icon. We must preach Christ and him crucified, the message that is foolishness to those who are perishing, but is the power of God to us who are being saved (cf. 1 Cor 1:18, 2:2).

Jodie McNeill is Director of the Youthworks Year 13 Gospel Gap Year