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. Author manuscript; available in PMC: 2015 Dec 17.
Published in final edited form as: Lancet. 2014 Feb 17;383(9930):1762–1770. doi: 10.1016/S0140-6736(13)61682-7

Table 1.

Hypothetical example of vaccine probe results for a pneumonia-causing pathogen

Incidence in unvaccinated people (IU) Incidence in vaccinated people (IV) Calculated vaccine effectiveness [VE = 1−(IV/IU)] Calculated aetiological fraction [AF = VE/VEc*] Vaccine-preventable disease incidence (VPDI = IU − IV)
Aetiologically confirmed disease   0.5   0.05 90% 100% 0.45
Pneumonia with alveolar infiltrate   2.0   1.28 36%   40% 0.72
Clinical severe pneumonia   8.0   6.2 23%   25% 1.8
All pneumonia 50.0 45.5   9%   10% 4.5
*

VEc=vaccine effectiveness for aetiologically confirmed cases. All incidence calculations are per 1000 person-years. Calculation of the aetiological fraction relied on the assumption that the vaccine worked equally well against all measured clinical outcomes caused by the pathogen.