The opposing effects of vaccination versus natural infection on the immune system likely reflect differences in the type or magnitude of the immune response induced including marked cell death among lymphocytes during measles infection that is not observed after vaccination59, possibly because vaccine and wild-type measles strains are recognized by different PRRs; TLR2 for wild-type measles versus TLR3 for vaccine strains60. Here, TLR2 is linked to measles.