A recently published study resulted in an article published in the Washington Post claiming certain vaccines make viruses more dangerous. The study was about what's termed a Leaky Vaccine used to protect chickens against Marek’s disease. This type of vaccine isn't used for human illnesses (yet), but how can a vaccine make viruses more dangerous? Dave Hawkes, Honorary Fellow at Department of Pharmacology and Therapeutics at University of Melbourne, Australia explains that "‘Leaky vaccines’ don’t affect the ability of the virus to reproduce and spread to others; they simply prevent it from causing disease." So while the vaccine protects the vaccinated bird, unvaccinated birds may be more likely to be exposed to the virus. Unfortunately, if you're a chicken, Marek’s disease has a very high fatality rate...
theconversation.com/are-vac...
Given Dave Hawkes says "But yet-to-be-developed vaccines for diseases such as HIV, Ebola or malaria, where humans have been unable to mount an effective natural defence, are likely to be leaky", this is an area of vaccination research that we should take an interest in.
Neil