All vaccines are effective to a certain extent and for a certain length of time. These numbers are often skewed to make vaccines seem more effective and to last longer then they have actually proven to be. This skewed information makes the actual effectiveness of any vaccine difficult to ascertain as it is often buried in order to sell more of the vaccine in question.
A malaria vaccine may be effective, but we do not have one that works now. Many mosquitoes have become resistant to pesticides that used to kill them, thus increasing the number of people with malaria. Scientists and doctors are optimistic that a vaccine will work because people who are exposed outside the country have developed immunity to disease and death. While this doesn't prevent symptoms of malaria, many people can live without symptoms. Clinical trials have also been making progress with the vaccine.