There was no credible evidence behind claims of harm from the MMR ( measles, mumps and rubella ) vaccination.
This is the conclusion drawn by the Cochrane Review Authors, an international team of researchers, after carefully drawing together all of the evidence found in 31 high quality studies from around the world. They also highlight that the policy of encouraging mass use of MMR has eliminated the scourge of measles, mumps and rubella from many countries.
" In particular we conclude that all the major unintended events, such as triggering Crohn's disease or autism, were suspected on the basis of unreliable evidence," says lead author Vittorio Demicheli who works at Servizo Sovrazonale di Epidemiologia, Alessandria, Italy.
The MMR vaccine was introduced in the USA in the 1970s and is now in use in over 90 countries around the world.
A single research paper published in 1998 based on 12 children cast doubt on the safety of the vaccine by implying that it might cause development problems like Crohn's disease and autism.
The paper has since been retracted by most of the original authors, but before that it triggered a worldwide scare, which in turn resulted in reduced uptake of the vaccine.
Aware of the controversy surrounding the use of MMR, members of The Cochrane Collaboration set out to review the evidence for effectiveness of the vaccine and also to review evidence of adverse events.
In a process of 'systematic reviewing' researchers searched international databases and found 139 articles about MMR use.
Because many of them referred to studies that had been conducted in a way that could not rule out bias or error, the researchers discarded all but 31 of them.
Using rigorously established methods the researchers then synthesised the findings from these pieces of higher-quality research to create the most authoritative assessment yet available.
The systematic review's key findings are that:
1. There is no credible link between the MMR vaccine and any long-term disability, including Crohn's disease and autism.
2. MMR is an important vaccine that has prevented diseases that still carry a heavy burden of death and complications where the vaccine is not used consistently.
3. The lack of confidence in MMR has caused great damage to public health.
4. People arguing for or against the use of any therapy need to make sure that they base their conclusions on carefully collected evidence, not just on biased opinion, speculation or suspicion.
Source: Cochrane Library, 2005