Pneumococcal vaccines in adults: assessing the evolving evidence

Pneumonia and Invasive Pneumococcal Diseases: The Role of Pneumococcal Conjugate Vaccine in the Era of Multi-Drug Resistance

Streptococcus pneumoniae related diseases are a leading cause of morbidity and mortality, especially in children and in the elderly population. It is transmitted to other individuals through droplets and it can spread to other parts of the human host, causing a wide spectrum of clinical syndromes, affecting between 10 and 100 cases per 100,000 people in Europe and the USA. In order to reduce morbidity and mortality caused by this agent, pneumococcal vaccines have been developed over the years and have shown incredible effectiveness in reducing the spread of this bacterium and the development of related diseases, obtaining a significant reduction in mortality, especially in developing countries. However, considerable problems are emerging mainly due to the replacement phenomenon, multi-drug resistance, and the high production costs of conjugated vaccines. There is still a debate about the indications given by various countries to different age groups; this is one of the reasons for the diffusion of different serotypes. To cope with these problems, significant efforts have been made in the research field to further improve vaccination serotypes coverage. On the other hand, an equally important commitment by health care systems to all age group populations is needed to improve vaccination coverage.

An intervention to improve pneumococcal vaccination uptake in high risk 50-64 year olds vs. expanded age-based recommendations: an exploratory cost-effectiveness analysis

In the U.S., pneumococcal polysaccharide vaccine (PPSV23) uptake among high-risk adults aged <65 years is consistently low and improvement is needed. One barrier to improved vaccine coverage is the complexity of the adult vaccination schedule. This exploratory analysis compared the cost-effectiveness of strategies to increase pneumococcal vaccine uptake in high-risk adults aged 50-64 years. We used a Markov model to compare strategies for non-immunocompromised 50-64 year olds: 1) current pneumococcal polysaccharide vaccine (PPSV23) recommendations; 2) current recommendations enhanced by an intervention; 3) PPSV23 plus pneumococcal conjugate vaccine (PCV13) for high-risk patients with no intervention; or 4) both vaccines for all 50-year-olds with no intervention. Parameters included CDC data and other US data, varied extensively in sensitivity analyses. In the analysis, vaccinating high-risk individuals with PPSV23/PCV13 was the least costly strategy, with total costs of $424/person. Vaccinating all 50 year olds with PPSV23/PCV13 cost $40 more and gained 0.00068 quality-adjusted life years (QALY), or $57,786/QALY gained. Current recommendations with or without an intervention program were more expensive and less effective than other strategies. In multi-way sensitivity analyses, the current recommendations/intervention program strategy was favored at a $100,000/QALY threshold only if non-bacteremic pneumococcal pneumonia rate or PCV13 serotype coverage were substantially lower than base case values. Thus, an intervention program to improve pneumococcal vaccine uptake among high-risk 50-64 year-olds was not cost-effective in most scenarios. High-risk individuals receiving both PCV13 and PPSV23 could be economically favorable, and vaccinating all 50-year-olds with both vaccines could be considered.

Decreased relative risk of pneumococcal pneumonia during the last decade, a nested case-control study

Background

Streptococcus pneumoniae (SP) is one of the most common pathogens of Community-Acquired Pneumonia (CAP), but recent reports suggest that its incidence may be declining in relation to the use of the conjugate 13-valent pneumococcal vaccine in children. We compared the result of the immunochromatographic SP urinary antigen test (SPUAT) and clinical outcomes in patients with CAP admitted in two periods of time: 2001–2002(CAP1) and 2015–2016(CAP2).

Methods

This was a matched nested case-control study of two prospectively recorded cohorts of patients admitted with CAP, with SPUAT and blood culture performed in all patients. CAP2 cases and CAP1 controls were matched for age ± 4 years, sex, and Pneumonia Severity Index (PSI) score ± 10 points. Odds ratios (OR) for having SPUAT positive was estimated by conditional logistic regression. A multivariate model assessed the contribution of individual variables.

Results

Four hundred ninety-eight patients were recruited; 307 during the CAP1 and 191 during the CAP2 periods. Comparing both periods we observed differences, in age, PSI score, and the percentage of smokers, outpatients, previously immunized with pneumococcal vaccine, and positive SPUAT. On the other hand, mortality, admission from nursing homes, pneumococcal bacteremia and hospital admission were not different. After matching, pneumonia due to SP per the SPUAT was observed in 34(23.4%) of CAP1 and in 12(8.3%) of CAP2 patients (p < 0.001), and 6/145 CAP1 vs 33/145 CAP2 patients had received pneumococcal immunization before their admission (p < 0.001). A multivariate analysis confirmed that, independent of falling into PSI class 5, having not received the pneumococcal vaccine and having not survived the episode of pneumonia, there were two factors that increased the probability of having SPUAT positive: developing pneumonia during the CAP1 period (OR = 1.23) and having pneumococcal bacteremia (OR = 2.66).

Conclusion

We observed a reduction of the role of SP as pathogen, along with an increase in the number of patients who received pneumococcal immunization before admission, in 2015-2016 compared to 2001-2002. In addition, the use of conjugate 13-valent vaccine, starting in 2012 for childhood immunization, could be an additional factor contributing to these changes, as a result of early herd immunity in adults pneumonia.

Pneumococcal vaccination and chronic respiratory diseases

Patients with COPD and other chronic respiratory diseases are especially vulnerable to viral and bacterial pulmonary infections, which are major causes of exacerbations, hospitalization, disease progression, and mortality in COPD patients. Effective vaccines could reduce the burden of respiratory infections and acute exacerbations in COPD patients, but what is the evidence for this? This article reviews and discusses the existing evidence for pneumococcal vaccination efficacy and its changing role in patients with chronic respiratory diseases, especially COPD. Specifically, the recent Community-Acquired Pneumonia Immunization Trial in Adults (CAPITA) showed the efficacy of pneumococcal conjugate vaccine in older adults, many of whom had additional risk factors for pneumococcal disease, including chronic lung diseases. Taken together, the evidence suggests that pneumococcal and influenza vaccinations can prevent community-acquired pneumonia and acute exacerbations in COPD patients, while pneumococcal vaccination early in the course of COPD could help maintain stable health status. Despite the need to prevent pulmonary infections in patients with chronic respiratory diseases and evidence for the efficacy of pneumococcal conjugate vaccine, pneumococcal vaccine coverage and awareness are low and need to be improved. Respiratory physicians need to communicate the benefits of vaccination more effectively to their patients who suffer from chronic respiratory diseases.

Preventing pneumococcal disease in the elderly: recent advances in vaccines and implications for clinical practice

Streptococcus pneumoniae remains a major cause of morbidity and mortality throughout the world. To date, after the introduction of routine childhood immunization, elderly people (i.e., persons aged 65 years or older) suffer the greatest burden of pneumococcal disease in developed countries. At present, two anti-pneumococcal vaccines are available for use in adults: the 23-valent pneumococcal polysaccharide vaccine (PPV23) and the 13-valent protein-polysaccharide conjugate vaccine (PCV13). This article reviews current data about the burden of pneumococcal disease in the elderly, as well as evidence for immunogenicity, clinical efficacy, and possible cost-effectiveness of both vaccines. The main advantage of PCV13 is that it may be more effective than PPV23, but a major limitation is that it is directed against strains that are likely to be greatly reduced in the population since its introduction in childhood immunization. The main disadvantage of PPV23 is that it may be less effective than PCV13 against vaccine-type infections but a major advantage is that it may provide protection against ten additional serotypes. To date, expert committees have not changed recommendations for pneumococcal vaccination in adults. However, at present, they are evaluating different alternatives (basically, maintaining PPV23, changing from PPV23 to PCV13 in some groups, or adding PCV13 for all or some target adult population subgroups). Critical data (clinical efficacy reported in ongoing trials and magnitude of indirect effects of pediatric PCV13 programs) needed to make a well-informed decision could be available during 2013. Considering all concerns over indirect effects and replacement strains following the use of polysaccharide-based vaccines, efforts should be directed toward developing vaccines, such as protein-based pneumococcal vaccines, with potential serotype-independent protection. Meanwhile, according to current recommendations, PPV23 should continue to be used for high-risk adults and all elderly people (with and without additional high-risk conditions). Although it is only moderately effective, it has a considerable serotype coverage and at-risk persons can benefit from the vaccination. High-risk individuals could also obtain a benefit from adding PCV13, but more data are needed before a universal recommendation can be made.

Pneumococcal conjugate vaccination for older adults: Reply letter to Hollingsworth et al

Hollingsworth and Isturiz (1) have raised several questions about our earlier review of the use of pneumococcal conjugate (PCV) or polysaccharide (PPV) vaccine for older adults (i.e., ≥65 y of age). (2) They begin by citing two metaanalyses published in 2009 and 2013 that concluded that prevention of pneumococcal pneumonia could not be demonstrated for PPV. (3)(,) (4) They overlook my earlier review of five metaanalyses that was published in 2004. (5) This review showed that the study populations in prospective trials of PPV were often not representative of the populations of elderly and high-risk adults for whom PPV is recommended. Furthermore, the five metaanalyses often omitted clinical trials that should have been evaluated, included trials that should have been omitted, and frequently miscounted the numbers of subjects and outcome events in the individual clinical trials. More important, retrospective sample size calculations showed that none of the five metaanalyses included an adequate number of person years of observation to rule out false-negative results. The numbers speak for themselves and cannot be ignored. Simply put, metaanalyses of the PPV clinical trials will never tell us whether the vaccine prevents pneumococcal pneumonia or all-cause pneumonia in elderly and high-risk adults, and consequently they must be regarded as inconclusive and uninformative. Since 2004, only one small prospective clinical trial of PPV has been published (reviewed in 6). Nothing new has been added to our knowledge of PPV efficacy by the more recent metaanalyses. (3)(,) (4) Epidemiologists have reminded us that the lack of evidence of PPV efficacy is not evidence of its absence. The conclusions of our earlier review still stand. (5.)

Pneumococcal polysaccharide 23-valent vaccine: long-term persistence of circulating antibody and immunogenicity and safety after revaccination in adults

Since publication of a 1997 review of the immunogenicity and safety data for pneumococcal polysaccharide vaccines (PPSVs), dozens of additional studies have been published, involving larger cohorts, longer observation periods, and more specific assays. Additionally, a 13-valent pneumococcal conjugate vaccine (PCV) has been licensed for adults. This paper reviews adult studies assessing antibody persistence for ≥ 3 years after pneumococcal vaccination, and adult studies of immunogenicity and safety after revaccination. This review emphasizes the currently registered PPSV23 formulations containing 25-μg polysaccharide per serotype, for which far more long-term data are available. Broadly, IgG and functional antibody levels after PPSV23 in adults persist above concentrations in unvaccinated adults for at least 5-10 years in most studies. The few exceptions involve populations of non-ambulatory adults or those with confounding host-factor issues. Revaccination with PPSV23 5-10 years after a previous dose consistently and substantially increases both IgG and functional antibody levels. There is an inverse association between circulating antibody level just before primary or revaccination and subsequent antibody increase. Although injection-site reactions (e.g., pain, swelling, redness) were reported more commonly after PPSV23 revaccination than after primary vaccination in most studies, these reactions typically resolved within 5 days. We interpret the contemporary literature as supporting pneumococcal revaccination as a means to sustain anti-pneumococcal antibodies at levels greater than among unvaccinated adults. PPSV23 is a broad-spectrum public-health tool to help prevent serious pneumococcal diseases across the adult lifespan.