According to a new study, faulty vaccines could lead to the evolution of more virulent and hazardous infectious agents that spread disease. The findings have been published in the online journal Public Library of Science Biology. As per reports, it discusses the transmission of bird flu to humans in addition to vaccine strategies for controlling Ebola, HIV and malaria.

It was found by them that a "leaky" vaccine against Marek's disease helped saving treated birds, however, the virus survived and killed unvaccinated birds.

As per British investigator Professor Venugopal Nair, from The Pirbright Institute near Woking, Surrey, their study shows that the use of leaky vaccines could lead to the evolution of awful 'hot' viral strains which pose greater risk to unvaccinated individuals.

It is said that childhood vaccines for polio, smallpox, rubella, mumps and measles are "perfect" for the reason that they provide protection to vaccinated individuals and also prevent them from infecting others.

However, with other kinds of "leaky" vaccine, the recipient may experience mild symptoms. As per reports, this type of vaccine controls virulent strains of bird flu, which could pose a potential risk to humans.

According to study co-author Professor Andrew Read, from Pennsylvania State University in the US, "We humans never have experienced any contagious disease that kills as many unvaccinated hosts as these poultry viruses can, but we now are entering an era when we are starting to develop next-generation vaccines". He said that these injections are leaky for the reason that they are for diseases, which usually do not produce strong natural immunity.