Trends in the burden of IPD
A conjugated pneumococcal vaccine covering 13 serotypes (13vPCV) is used in the Australian paediatric immunisation program, and a polysaccharide vaccine covering 23 serotypes (23vPPV) is more commonly used in older people and high-risk groups.
The use of pneumococcal vaccines in infants, initially a conjugate pneumococcal vaccine containing seven serotypes (7vPCV) and then conjugate vaccine containing 13 serotypes (13vPCV), has led to a decrease in carriage of the serotypes in these vaccines (‘vaccine types’) and also to a decrease in vaccine-type disease in older people through herd immunity. For example, an Australian review of IPD trends in non-Indigenous older people showed an ongoing substantial decrease in IPD due to the serotypes in 7vPCV since its introduction in 2004. A similar trend was evident against the additional six serotypes in 13vPCV after only three years of its use, and further decline continues.3 A meta-analysis of the indirect effects of conjugated vaccines found the mean time taken to attain a 90% reduction in vaccine-type IPD was 8.9 years for 7vPCV serotypes and 9.5 years for the additional serotypes in 13vPCV but not 7vPCV.4 Conversely, likely as a result of serotype replacement, the proportion of cases of IPD attributable to serotypes in 23vPPV but not 13vPCV is increasing, in Australia from 19% to 27%.3
Trends in the burden of community-acquired pneumonia
Although data on pneumococcal CAP are more limited than those on IPD and somewhat inconsistent, a decline in CAP caused by 13vPCV vaccine types is also expected as a result of the childhood vaccination program. This decrease has already been seen in unvaccinated young adults and older people in some studies.
For example, a cohort study of cases of nonbacteraemic pneumococcal pneumonia in adults in Nottingham, UK, described a 30% reduction in the proportion of cases caused by 13vPCV vaccine types within three years of the switch from 7vPCV to 13vPCV in the childhood program. This followed an 88% decrease in CAP caused by 7vPCV vaccine types.5 In the US, an assessment of the impact of childhood 7vPCV, using the Nationwide Inpatient Sample database, found an annual reduction in pneumonia hospitalisations of 168,000, with most of these hospitalisations in older people.6
By ensuring patients aged 65 years and above are made aware of their increased risk of IPD and strongly encouraging vaccination against pneumococcal disease, GPs play a crucial role in helping reduce the pneumococcal burden
Associate Professor John Litt,
GP, Flinders University
Vaccine effectiveness against community-acquired pneumonia
Published estimates place the burden of hospitalisation due to CAP as at least an order of magnitude greater than that due to IPD.2 Thus, the benefit of vaccines against CAP is important in determining approaches to vaccination of older people, even if the burden of disease is decreasing due to immunity to the serotypes in 13vPCV.
Vaccine effectiveness data for 13vPCV against CAP are available from the CAPITA study, a randomised controlled trial in people aged 65 years and over in the Netherlands. The study found a vaccine effectiveness of 45% against vaccine-type pneumococcal CAP, 22% against all-type pneumococcal CAP and 5% against all-cause CAP.7
Clinical studies and review documents have variously ascribed impacts of 23vPPV against pneumococcal CAP from no effect through to about 50% in many studies. Although the studies have methodological challenges and are difficult to compare, the weight of evidence from the ‘better’ studies suggests that the attributable vaccine effectiveness is not zero and is in the range up to 50%. For example, a multicentre Japanese study reported the vaccine effectiveness as 33%.8 Protection against all-cause CAP with both vaccine types is similar and low, about 5%.9,10
Which vaccine(s) should we use in older people?
Current recommendations on pneumococcal vaccination in older people, developed by the Australian Technical Advisory Group on Immunisation (ATAGI) and published in the Australian Immunisation Handbook, vary depending on whether they have medical or other conditions that increase their risk of IPD.11 Under ATAGI guidelines, there are two categories of increased IPD risk: A and B (described in Box 1).11 Recommendations according to risk level are as follows.