PCV vaccines

Disease (incidence) rates are higher in Africa than in Europe or North America, incidence rates in Asia and Latin America range in between. Before widespread PCV introduction in 2006, mean annual incidence of invasive pneumococcal disease in children <2 years was 44/100,000 in Europe, 167/100,000 in the USA, 60 - 797/100,000 in Africa (SA and Mozambique). The reported incidence in countries in Asia and Latin America falls between these extremes. Some of the differences in disease incidence could be due to differences in surveillance methods. ^{Go to footnote 11, Go to footnote 22, Go to footnote 33, Go to footnote 44, Go to footnote 55}    

The introduction of the pneumococcal conjugate vaccine into childhood immunization programmes starting in 2000 led to substantial reductions in the overall IPD incidence in many countries due to reductions in the incidence of vaccine serotype (vaccine-type(s), VT) disease. IPD reductions were also observed in unvaccinated children and adults through herd protection in some countries. Declines in the incidence of VT disease were accompanied by increases in IPD caused by non-vaccine serotypes (NVTs), known as serotype replacement; however, among children, the increase in incidence of IPD due to NVTs was smaller than the decline in VT IPD, resulting in a decline in the overall incidence of IPD.  ^{Go to footnote 66}

To note is that the incidence estimates are driven by clinical practices in the country and whether rates are limited to inpatients or also include outpatients. For example, in the US there is a lower threshold than in Europe to do blood cultures, and this impacts incidence rates. Most cases in the US are outpatients with febrile bacteraemia, which can be self-limiting. On the other hand, the cases in Africa may mainly be from inpatients with sepsis or bacteremic pneumonia.