Pneumococcal conjugate vaccine for adults: “It's tough to make predictions, …”

Abstract

@ERSpublications Do the results of the CAPITA study justify the general vaccination of adults with PCV13? http://ow.ly/RW74T"… especially about the future." This frequently used Yogi Berra quote also holds true for the paper by MANGEN et al.[1] from the Netherlands, which modelled the cost-effectiveness of a potential vaccination programme for elderly adults using the 13-valent pneumococcal conjugate vaccine.The 13-valent pneumococcal conjugate vaccine (PCV13) was licensed for adults in 2011. Data from the largest randomised controlled trial (RCT) on a pneumococcal vaccine published to date (the CAPITA study) show a vaccine efficacy of 45.6% for pneumonia caused by the 13 vaccine serotypes, including 45.0% for non-bacteraemic pneumonia [2]. Do these data justify the general use of PCV13 in adults? MANGEN et al.[1] conducted economic modelling mainly based on the data of the CAPITA study that showed that PCV13 in adults is highly cost-effective. However, vaccination of infants, the main reservoir of pneumococci, with conjugate vaccines has resulted in herd protection effects, i.e. also decreased prevalence of the serotypes contained in vaccine in adults. Undoubtedly, community-acquired pneumonia (CAP) is a major public health topic, including in developed countries. Its morbidity and mortality increase with age [3]. Most studies have found Streptococcus pneumoniae to be the most frequent pathogen in CAP [4]. Therefore, an effective vaccine against S. pneumoniae for elderly adults would be a breakthrough for CAP prevention. However, S. pneumoniae is a smart pathogen: its main virulence factor is a polysaccharide capsule that prevents recognition by phagocytes. Not only are polysaccharides are of limited immunogenicity when used as vaccine antigens, there are also 94 known different capsular types with no or very limited cross-immunity [5].Earlier vaccination strategies against S. pneumoniae involved administering large amounts of pure polysaccharide. The 23-valent polysaccharide (PPV23) vaccine contains the polysaccharides of 23 out of the 94 serotypes. However, its efficacy was not convincing, probably because polysaccharides are primary B-cell antigens and therefore vaccination does not induce a T-cell response, resulting in a lack of both memory cells and mucosal immunity [6,7]. In addition, this vaccine could not be used in younger infants, because their immature immune system did not properly respond to this vaccine. However, several meta-analyses of RCTs have shown that PPV23 has a efficacy of up to 75% against pneumococcal bacteraemia [8,9]. Interestingly, we found the same efficacy in our CAPNETZ (German Network for community-acquired pneumonia) cohort, which was not included in these meta-analyses [10].

What do we know about the cost-effectiveness of pneumococcal conjugate vaccination in older adults?

“…1 The cost-effectiveness of PCV13 use in older adults and the relative merits of PCV13 when compared to the 23-type pneumococcal polysaccharide vaccine (PPV23) has been a topic of much debate. [2][3][4][5][6][7][8][9][10][11] The costs and benefits of pneumococcal vaccination in adults are likely to rest on several critical parameters: the magnitude pneumococcal disease in older adults and the serotypes responsible for it, the efficacy of each vaccine against invasive and non-invasive pneumonia, the duration of vaccine protection, and differences in vaccine price.…”