Sometimes, putative medical adverse effects are regarded as controversial and generate heated discussions in society and lawsuits against drug manufacturers. One example is the recent controversy as to whether autism was linked to the MMR vaccine (or by thiomersal , a mercury -based preservative used in some vaccines ). No link has been found in several large studies, and despite removal of thimerosal from vaccines a decade ago the rate of autism has not decreased as would be expected if it had been the causative agent.  
A variety of infectious agents may be transmitted by transfusion. Definitive evidence of transmission by transfusion requires demonstration of seroconversion or new infection in the recipient and isolation of an agent with genomic identity from both the recipient and the implicated donor. Strong presumptive evidence of transfusion transmission includes recipient seroconversion within an appropriate interval after transfusion, the recognition of appropriate infectious markers in an implicated donor on follow-up investigation, or both. Transfusion transmitted disease should be reported to the Australian Red Cross Blood Service.