Complex sentence: Autism rates continued to rise in Japan after the discontinuation of the MMR vaccine, which disproves any large-scale effect of vaccination, and means that the withdrawal of MMR in other countries is unlikely to cause a reduction in autism cases.
Split into simpler sentences: Autism rates continued to rise in Japan after the discontinuation of the MMR vaccine. This can be interpreted as disproving the effect of vaccination, and means that the withdrawal of MMR in other countries is unlikely to cause a reduction in autism cases.