Unforseen Vaccine Effects

SAGE Advice

An interesting paradigm is developing in the vaccine literature between specific and non-specific effects of vaccination. Specific vaccine effects give disease protection and are independent of the order in which vaccines are given. Non-specific effects refer to the effects a vaccine might have on the overall immune system, which seems to depend on the order of vaccination.

Studies have suggested that mortality due to infection decreases when the most recent vaccine includes a living, attenuated virus and that mortality actually increases when the most recent vaccination is inactivated. Something about an immune response to a living entity seems to trigger a boost to the immune system.

In March of 2013, after several studies published evidence of non-specific effects of live vaccines, the World Health Organization (WHO) called together a Strategic Advisory Group of Experts (SAGE) working group to “review the evidence concerning the possible non-specific effects of vaccines included in the routine infant immunization schedule.”

Findings from Denmark

In addition to reviewing literature for the WHO, one of these SAGE Working Group members, Christine Stabell Benn, MD, PhD, has been busy working on her own studies of non-specific vaccine effects. She and her colleagues just published a study in the JAMA comparing hospital admittance for any infections between two cohorts of children.  One cohort received the vaccination regimen for live measles, mumps, rubella (MMR) as the most recent vaccine, while the other cohort received inactivated DTaP-IPV-Hib as their most recent vaccine. 

Benn and her colleagues found that children who had received the live MMR vaccine most recently had less hospital visits for infection than the children who had received inactivated DTaP-IPV-Hib.


If this effect is reproducible in other high-income communities, there is a chance that the SAGE Working Group will be able to recommend changes in vaccine policy that foster better patient outcomes. For high-income communities, this could mean less infections, less antibiotics, and less money spent on care. For low-income communities, it could be the difference between life and death.