Revaccination with Live Attenuated Vaccines Confer Additional Beneficial Nonspecific Effects on Overall Survival: A Review.

Wednesday, 10th of August 2016

EBioMedicine. 2016 Jul 15. pii: S2352-3964(16)30321-8. doi: 10.1016/j.ebiom.2016.07.016. [Epub ahead of print]

Revaccination with Live Attenuated Vaccines Confer Additional Beneficial Nonspecific Effects on Overall Survival: A Review.

Benn CS¹ Fisker AB² Whittle HC³ Aaby P⁴.

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Abstract

BACKGROUND:

Live vaccines against measles (MV) tuberculosis (BCG) polio (OPV) and smallpox reduce mortality more than explained by target-disease prevention. The beneficial nonspecific effects (NSEs) of MV are strongest when MV is given in presence of maternal antibodies. We therefore hypothesized that revaccination in presence of prior immunity enhances beneficial NSEs.

METHODS:

Literature search for studies of revaccination and mortality.

FINDINGS:

In two randomised trials (RCTs) two doses versus one dose of MV reduced all-cause mortality by 63% (95% CI: 23-83%) from 9 to 18months of age. In a quasi-experimental study two doses before and after 9months compared with one dose of MV after 9months of age reduced mortality by 59% (25-81%). BCG-revaccination significantly enhanced BCGs effect against overall child mortality in two RCTs. In a natural experiment study of OPV campaigns over a 13-year-period in Guinea-Bissau each additional dose of OPV was associated with a 13% (4-21%) reduction in mortality rate. The beneficial NSEs of smallpox vaccination for survival increased significantly with the number of smallpox vaccination scars.

INTERPRETATION:

Revaccination with live vaccines led to substantial reductions in overall mortality. These findings challenge current understanding of vaccines and may explain the beneficial effects of campaigns with live vaccines.

Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.