We now have no polio in this country because enough people are immune to have communal resistance high. Let us look at malaria vaccines for one moment. It is possible to attack the plasmodium at several points in its life cycle. But so far, researchers have had trouble developing a safe and reliable vaccine. Some years ago a vaccine was developed, was slated for trial in the Gambia where many people had malaria.
Most difficulties arise where two perfectly proper principles come into conflict.
With immunisation generally we face the classic ethical dilemma. We face John Stuart Mill head on. On the one hand we understand the benefits to be gained from widespread immunisation. We know that some of the benefits come from raising general herd immunity and that this in turn comes from high levels of community practice of immunisation. On the other hand, we know that some parents and some practitioners actually disapprove of immunisation, and that some children, for technical reasons, cannot have immunisation carried out.