Table 3 

Numbers needed to vaccinate for preventing one case of community acquired pneumonia, acute myocardial infarction or ischaemic stroke by pneumococcal vaccination in people 60 years or older 

Outcome 
Attributable Risk per 1000 person/year 
Number Need to Vaccinate 



AR^{a} 
95% CI^{b} 
NNV^{c} 
95% CI (lower to higher^{d}) 



Community acquired pneumonia 
1.067 
1.139 to 3.327 
938 
306 to 878 


Acute myocardial infarction 
0.423 
1.341 to 2.187 
2,365 
458 to 746 


Ischaemic Stroke 
1.788 
0.177 to 3.399 
560 
295 to 5649 


^{a }Attributable Risk = incidence rate difference between unvaccinated and vaccinated subjects. ^{b }CI denotes confidence interval. ^{c }NNV is the number needed to vaccinate for preventing one case and is estimated as 1/AR. ^{d }The negative numbers in the high limit of confidence interval indicate that NNV tends to infinite and it is not statistically significant. 

VilaCorcoles et al. BMC Public Health 2012 12:222 doi:10.1186/1471245812222 