Vaccinia scars associated with better survival for adults. An observational study from Guinea-Bissau

Abstract

Background: Live vaccines including BCG and measles may have non-targeted beneficial effects on childhood survival in areas with high mortality. The authors therefore undertook a survey of vaccinia scars to evaluate subsequent mortality.

Subjects: Based on a population census, a cohort of 1893 adults in urban Guinea-Bissau was examined in 1998 and followed until 2002.

Main outcome measure: All cause mortality, excluding accidents.

Results: The median age of vaccinia vaccinations had been 16-18 years. Adults with a vaccinia scar had a mortality ratio (MR) of 0.60 (0.41-0.87) compared to those without any scar. The effect was stronger for women. Mortality decreased with each additional vaccinia scar (MR=0.73 (0.56-0.95)). Among 502 individuals with information on HIV infection, the age-adjusted HIV-2 prevalence was 2.45 (1.06-5.65) for those with a vaccinia scar. Control for district, ethnic group, schooling, place of birth, quality of housing and HIV status had little effect on the estimate. Since vaccinia and BCG scars could have been confused, mortality for adults with vaccinia and/or BCG scar was compared to those without, the MR being 0.61 (0.41-0.89).

Conclusion: Known cultural or socio-economic factors possibly associated with access to vaccination had no influence on the mortality ratio for having a vaccinia scar. Hence, vaccinia vaccination may have a prolonged beneficial effect on adult survival.