Determining the optimal pneumococcal vaccination strategy for adults: is there a role for the pneumococcal conjugate vaccine?

Immunosenescence and human vaccine immune responses

The age-related dysregulation and decline of the immune system-collectively termed "immunosenescence"-has been generally associated with an increased susceptibility to infectious pathogens and poor vaccine responses in older adults. While numerous studies have reported on the clinical outcomes of infected or vaccinated individuals, our understanding of the mechanisms governing the onset of immunosenescence and its effects on adaptive immunity remains incomplete. Age-dependent differences in T and B lymphocyte populations and functions have been well-defined, yet studies that demonstrate direct associations between immune cell function and clinical outcomes in older individuals are lacking. Despite these knowledge gaps, research has progressed in the development of vaccine and adjuvant formulations tailored for older adults in order to boost protective immunity and overcome immunosenescence. In this review, we will discuss the development of vaccines for older adults in light of our current understanding-or lack thereof-of the aging immune system. We highlight the functional changes that are known to occur in the adaptive immune system with age, followed by a discussion of current, clinically relevant pathogens that disproportionately affect older adults and are the central focus of vaccine research efforts for the aging population. We conclude with an outlook on personalized vaccine development for older adults and areas in need of further study in order to improve our fundamental understanding of adaptive immunosenescence.

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.

Decision-making for PCV in adults

Thirteen-valent pneumococcal conjugate vaccine (PCV13) was licensed in adults to address the unmet medical need of vaccine-type community acquired pneumonia (CAP) and the limitations of previous plain-polysaccharide vaccines. Since then, some have questioned the utility of adult PCV13 use, arguing that: i) high PCV13 uptake in young children would provide indirect effects that, by themselves, would sufficiently protect unvaccinated adults and ii) no data describing the real-world effectiveness of PCV13 use in adults, especially with immunocompromising conditions, exist. Even in countries like the United States where PCV13 has been routinely recommended for all adults aged ≥ 65 years, the recommendation is contingent on a re-evaluation to determine if continued use is needed in the context of a mature PCV13 pediatric immunization program. Emerging evidence, however, suggests that i) a meaningful burden of PCV13-type pneumococcal pneumonia still persists in adults at increased risk for pneumococcal disease, despite indirect effects from long-standing pediatric PCV13 use, ii) adult PCV13 use is effective and has reduced pneumococcal CAP, even in the elderly and those with chronic medical or immunocompromising conditions – and disease could come back if PCV13 were removed, and iii) ethical and pragmatic vaccine policy considerations support continued adult PCV13 use in countries that have already introduced the vaccine (eg, disparities in adult PCV13 uptake, confusion stemming from removing a previously-recommended vaccine for a non-safety-related concern, and the reality that next-generation PCVs are only a few years away). Together, these findings suggest that continued PCV13 vaccination in adults is needed to control vaccine-type CAP.

Cost-Utility Study of PCV13 Versus PPSV23 in Adults in Chile

INTRODUCTION

Pneumococcal infections are a public health problem in older adults. In Chile there are two vaccines at this time, PPSV23 and PCV13. The first has lower immunogenicity and effectiveness in preventing pneumococcal pneumonia and a lower cost than PCV13.

OBJECTIVE

To determine the cost-effectiveness of PCV13 versus PPSV23 in adults 18 years old and over in the Chilean Health System.

MATERIAL AND METHOD

A cost-utility study was performed using the Markov model (population data for a time horizon of 10 years). Utilities and epidemiological data were obtained from the literature and costs from the Chilean Public sector. Vaccine's costs and quality-adjusted life years (QALYs) were determined and compared.

RESULTS

PCV13 vaccination program in adults (≥18 years), generated savings of $42,195 USD and an increase of 6,820 QALYs, avoiding 107 cases of bacteremia, 13 meningitis, 6,706 inpatient pneumonia, 4,509 outpatient pneumonia and 1,189 deaths compared to PPSV23 without variation on sensitivity analysis on high impact variables. For the subgroup of patients over 65 years old PCV13 generates savings of $ 32,105.94USD and produces 5,430 QALYs more compared to PPSV23.

CONCLUSION

PCV13 is dominant. A PCV13 vaccination program saves costs to the public system, reduces mortality and morbidity; these results are robust.

Pneumococcal Conjugate Vaccine Safety in Elderly Adults

Background

The 13-valent pneumococcal conjugate vaccine (PCV13) and the 23-valent pneumococcal polysaccharide vaccine (PPSV23) were both recommended to adults aged ≥65 years. The study examines adults ≥65 years for risk of adverse events (AEs) requiring medical attention following vaccination with PCV13 as compared with vaccination with PPSV23, a long-standing vaccine with a satisfactory safety profile.

Methods

The cohort study included 6 Vaccine Safety Datalink sites. The exposed person-time included follow-up time of the first PCV13 received by subjects age ≥65 years from January 1 to August 15, 2015. The comparator person-time included follow-up time after the first PPSV23 received by subjects of the same age during Janaury 1 to August 15 of each year of 2011–2015. The prespecified AEs included cardiovascular events, Bell’s palsy, Guillain-Barré syndrome, syncope, erythema multiforme, thrombocytopenia, cellulitis and infection, allergic reaction, and anaphylaxis. Inverse probability of treatment weighting–adjusted Poisson regression models was used to estimate the relative risk (RR) of each AE.

Results

A total of 313 136 doses of PCV13 and 232 591 doses of PPSV23 were included. The adjusted RRs comparing the incidence of AEs following PCV13 vs PPSV23 were all <1, except for anaphylaxis, which was insignificant with an RR of 1.32 (95% confidence interval, 0.30–5.79). Only 1 patient who received PCV13 and 4 other vaccines concomitantly was confirmed by medical chart review as having experienced anaphylaxis after vaccination.

Conclusions

These data do not support an increased rate of adverse events following PCV13 administration in elders compared with PPSV23 and should provide reassurance regarding continued use of PCV13.

Pneumococcal conjugate vaccine use for the prevention of pneumococcal disease in adults <50 years of age

INTRODUCTION

Adults, particularly those with underlying chronic conditions, eg, cardiovascular, liver, and pulmonary diseases and diabetes mellitus, have a persistent pneumococcal disease burden. Thirteen-valent pneumococcal conjugate vaccine (PCV13) is recommended in the United States for all adults aged ≥65 years and immunocompromised adults aged <65 years to protect against vaccine-serotype (VT) invasive pneumococcal disease (IPD) and pneumonia. PCV13 is not recommended for immunocompetent adults aged ≥18 years with comorbidities associated with increased pneumococcal disease risk.

AREAS COVERED

This US-focused review summarizes PCV13-type IPD and community-acquired pneumonia burden in adults aged <50 years, PCV13 immunogenicity and safety in this population, and adult pneumococcal vaccination recommendations.

EXPERT COMMENTARY

Considering (i) PCV13 has demonstrated efficacy against VT-IPD and pneumonia in adults aged ≥65 years (with or without underlying chronic conditions), and (ii) immune responses to PCV13 in younger adults are comparable or better than in older adults, PCV13 would likely have similar efficacy in adults aged <50 years. Recommending PCV13 for at-risk adults aged <50 years would provide direct immunologic benefit of a conjugate vaccine and could address an important unmet medical need for pneumococcal pneumonia prevention. Although not directly addressed here, this benefit would likely extend to at-risk adults aged 50-64 years.

Rethinking number-needed-to-vaccinate for pneumococcal conjugate vaccines in older adults: Current and future implications

BACKGROUND

Number-needed-to-vaccinate (NNV) is increasingly used to inform decisions about vaccine use, but it is not calculated uniformly across studies. This study compared two methodologies for calculating NNV with 13-valent pneumococcal conjugate vaccine (PCV13) to prevent one case of community-acquired pneumonia (CAP) among US adults aged ≥65years: (i) using one-year absolute rate differences as was originally performed by the Centers for Disease Control and Prevention (CDC) and (ii) using absolute risk reduction over 5years.

METHODS

We constructed a hypothetical fixed cohort of 200,000 adults aged ≥65years equally separated into PCV13-vaccinated and PCV13-unvaccinated groups. We incorporated the same conservative assumptions used by CDC in 2014 regarding annual incidence of hospitalized (1375 per 100,000) and outpatient (2010 per 100,000) CAP, the initial (2014) proportion of adult PCV13-type CAP (10%), and PCV13 efficacy against vaccine-type CAP (45%). To model PCV13 impact over time, we assumed annual mortality was 5% for both groups, the percentage of adult PCV13-type CAP declined annually due to pediatric herd effects, and PCV13 efficacy did not wane over 5years.

RESULTS

Among adults aged ≥65years, NNV with PCV13 to prevent one hospitalized and one outpatient case of CAP as originally calculated by CDC in 2014 were 1620 and 1110, respectively. Accounting for 5-year cumulative effects, NNV with PCV13 to prevent one hospitalized and one outpatient case of CAP over 5years were 576 and 394, respectively. These revised NNV estimates are roughly one third of initial estimates in which cumulative effects were ignored. NNV to prevent any CAP (inpatient or outpatient) over 5years with one PCV13 dose was 234.

CONCLUSION

Accounting for cumulative preventive effects of PCV13 vaccination over time is critical. Failing to do so, even when using conservative disease burden parameters, can grossly underestimate the public health impact of adult PCV13 use.

Cost Effectiveness of the 13-Valent Pneumococcal Conjugate Vaccination Program in Chronic Obstructive Pulmonary Disease Patients Aged 50+ Years in Spain

Background

Patients with chronic obstructive pulmonary disease (COPD) are at elevated risk of pneumococcal infection. A 13-valent pneumococcal conjugate vaccine (PCV13) was approved for protection against invasive disease and pneumonia caused by Streptococcus pneumoniae in adults. This study estimated the incremental cost-effectiveness ratio (ICER) of vaccinating COPD patients ≥50 years old with PCV13 compared with current vaccination policy (CVP) with 23-valent pneumococcal polysaccharide vaccine.

Methods

A Markov model accounting for the risks and costs for all-cause non-bacteremic pneumonia (NBP) and invasive pneumococcal disease (IPD) was developed. All parameters, such as disease incidence and costs (€; 2015 values), were based on published data. The perspective of the analysis was that of the Spanish National Healthcare System, and the horizon of evaluation was lifetime in the base case. Vaccine effectiveness considered waning effect over time. Outcomes and costs were both discounted by 3 % annually.

Results

Over a lifetime horizon and for a 629,747 COPD total population, PCV13 would prevent 2224 cases of inpatient NBP, 3134 cases of outpatient NBP, and 210 IPD extra cases in comparison with CVP. Additionally, 398 related deaths would be averted. The ICER was €1518 per quality-adjusted life-year (QALY) gained for PCV13 versus CVP. PCV13 was found to be cost effective versus CVP from a 5-year modelling horizon (1302 inpatient NBP and 1835 outpatient NBP cases together with 182 deaths would be prevented [ICER €25,573/QALY]). Univariate and probabilistic sensitivity analyses confirmed the robustness of the model.

Conclusions

At the commonly accepted willingness-to-pay threshold of €30,000/QALY gained, PCV13 vaccination in COPD patients aged ≥50 years was a cost-effective strategy compared with CVP from 5 years to lifetime horizon in Spain.

[Pneumococcal infections: Appraisal and perspectives in terms of adult vaccination]

Pneumococcal diseases are the first cause of bacterial infections in adult and in the aged adult. While its considerable morbi-mortality is potentially preventable through vaccination, the interest of anti-pneumococcal vaccination in these populations is still debated. Effectiveness appraisal of current anti-pneumococcal vaccines and the perspectives in terms of preventive strategies against Streptococcus pneumoniae infections in the adult population are presented.

Vaccination in the elderly: what can be recommended?

The age-associated increased susceptibility to infectious disease would suggest that vaccination should be a route to promote healthy aging and keep our seniors autonomous and independent. While vaccination represents a cost-effective and efficient strategy at community level, the ability of the immune system to mount a protective immune response is still unpredictable at the level of the individual. Thus, at a similar age, some individuals, including the elderly, might still be 'good' responders while some other, even younger, would definitely fail to mount a protective response. In this review, the current burden of vaccine-preventable diseases in the aging and aged population will be detailed with the aim to identify the ideal vaccine candidates over the age of 50 years. This article will conclude with potential strategies to reduce, as best as possible, this burden and the imperative need to overcome barriers in extending current vaccine coverage towards to a lifelong vaccine schedule.

Role of pneumococcal vaccination in prevention of pneumococcal disease among adults in Singapore

The burden of disease associated with Streptococcus pneumoniae infection in adults can be considerable but is largely preventable through routine vaccination. Although substantial progress has been made with the recent licensure of the new vaccines for prevention of pneumonia in adults, vaccine uptake rates need to be improved significantly to tackle adult pneumococcal disease effectively. Increased education regarding pneumococcal disease and improved vaccine availability may contribute to a reduction in pneumococcal disease through increased vaccination rates. The increase in the elderly population in Singapore as well as globally makes intervention in reducing pneumococcal disease an important priority. Globally, all adult vaccines remain underused and family physicians give little priority to pneumococcal vaccination for adults in daily practice. Family physicians are specialists in preventive care and can be leaders in ensuring that adult patients get the full benefit of protection against vaccine-preventable diseases. They can play a key role in the immunization delivery of new and routine vaccines by educating the public on the risks and benefits associated with vaccines. Local recommendations by advisory groups on vaccination in adults will also help to tackle vaccine preventable diseases in adults.

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.

Immunosenescence and pneumococcal disease: an imbalance in host-pathogen interactions

Respiratory infections are among the most important causes of morbidity and mortality from infectious diseases worldwide. The most common causative bacterium, Streptococcus pneumoniae, frequently colonises the upper respiratory tract, where it resides mostly asymptomatically. Occasionally, however, S pneumoniae can cause severe disease such as pneumonia. Local host immunity is essential to control colonising pathogens by preventing overgrowth, spread, and invasion. However, age-related immune deficits in elderly people, known as immunosenescence, might contribute to increased disease burden. We review present knowledge about immunosenescence in the respiratory tract against Gram-positive bacteria, particularly S pneumoniae. We discuss the possible underdetection of pneumococcal colonisation in elderly people, and suggest changes to present surveillance methods to improve understanding of the relation between colonisation and disease. We conclude that present knowledge about alteration of host-pathogen interactions by immunosenescence in the respiratory tract is insufficient, and that research is needed to enable improved measures for prevention.

Cost-effectiveness of pneumococcal conjugate vaccination in immunocompromised adults

OBJECTIVE

Pneumococcal disease is a significant problem in immunocompromised persons, particularly in HIV-infected individuals. The CDC recently updated pneumococcal vaccination recommendations for immunocompromised adults, adding the 13-valent pneumococcal conjugate vaccine (PCV13) to the previously recommended 23-valent pneumococcal polysaccharide vaccine (PPSV23). This analysis estimates the cost-effectiveness of pneumococcal vaccination strategies in HIV-infected individuals and in the broader immunocompromised adult group.

DESIGN

Markov model-based cost-effectiveness analysis.

METHODS

The model considered immunocompromised persons aged 19-64 years and accounted for childhood PCV13 herd immunity; in a separate analysis, an HIV-infected subgroup was considered. PCV13 effectiveness was estimated by an expert panel; PPSV23 protection was modeled relative to PCV13 effectiveness. We assumed that both vaccines prevented invasive pneumococcal disease, but only PCV13 prevented nonbacteremic pneumonia.

RESULTS

In all immunocompromised individuals, a single PCV13 cost $70,937 per quality adjusted life year (QALY) gained compared to no vaccination; current recommendations cost $136,724/QALY. In HIV patients, with a longer life expectancy (22.5 years), current recommendations cost $89,391/QALY compared to a single PCV13. Results were sensitive to variation of life expectancy and vaccine effectiveness. The prior recommendation was not favored in any scenario.

CONCLUSIONS

One dose of PCV13 is more cost-effective for immunocompromised individuals than previous vaccination recommendations and may be more economically reasonable than current recommendations, depending on life expectancy and vaccine effectiveness in the immunocompromised.

Randomized, single blind, controlled trial to evaluate the prime-boost strategy for pneumococcal vaccination in renal transplant recipients

Renal transplant recipients are at increased risk of developing invasive pneumococcal diseases but may have poor response to the 23-valent pneumococcal polysaccharide vaccine (PPV). It may be possible to enhance immunogenicity by priming with 7-valent pneumococcal conjugate vaccine (7vPnC) and boosting with PPV 1 year later. In a randomized single-blind, controlled study, adult recipients of renal transplants received either 7nPVC or PPV followed by PPV 1 year later. The vaccine response was defined as 2-fold increase in antibody concentration from baseline and an absolute post-vaccination values ≥1 µg/ml. The primary endpoint was vaccine response of the primed group (7vPnC/PPV) compared with single PPV vaccination. Antibody concentrations for 10 serotypes were measured at baseline, 8 weeks after first vaccination, before second vaccination, and 8 weeks after second vaccination. Of 320 screened patients, 80 patients were randomized and 62 completed the study. Revaccination with PPV achieved no significant increase of immune response in the 7vPnC/PPV group compared with the single PPV recipients A response to at least 1 serotype was seen in 77.1% of patients who received 7vPnC and 93.1% of patients who received PPV (P = 0.046). After second vaccination response to at least 1 serotype was seen in 87.5% patients of 7vPnC/PPV group and 87.1% patients of PPV group (non significant p). The median number of serotypes eliciting a response was 3.5 (95% CI 2.5–4.5) in the 7vPnC/PPV group versus 5 (95% CI 3.9–6.1) in the PPV group (non-significant p). Immunogenicity of pneumococcal vaccination was not enhanced by the prime–boost strategy compared with vaccination with PPV alone. Administration of a single dose of PPV should continue to be the standard of care for adult recipients of renal transplants.

Trial Registration

EudraCT 2007-004590-25.

Long-term comparative immunogenicity of protein conjugate and free polysaccharide pneumococcal vaccines in chronic obstructive pulmonary disease

BACKGROUND

Although the 23-valent pneumococcal polysaccharide vaccine (PPSV23) protects against invasive disease in young healthy persons, randomized controlled trials in chronic obstructive pulmonary disease (COPD) have demonstrated no benefit in the intention-to-treat population. We previously reported that the 7-valent diphtheria-conjugated pneumococcal polysaccharide vaccine (PCV7) is safe and induced greater serotype-specific immunoglobulin G (IgG) and functional antibody than did PPSV23 1 month after vaccination. We hypothesized that these advantages would persist at 1 and 2 years.

METHODS

One hundred eighty-one patients with moderate to severe COPD were randomized to receive PPSV23 (n = 90) or PCV7 (1.0 mL; n = 91). We measured IgG by enzyme-linked immunosorbent assay and assessed functional antibody activity by a standardized opsonophagocytosis assay, reported as a killing index (OPK). We determined differences in IgG and OPK between vaccine groups at 1 and 2 years.

RESULTS

Relative to PPSV23, PCV7 induced greater OPK at both 1 and 2 years for 6 of 7 serotypes (not 19F). This response was statistically greater for 5 of 7 serotypes at 1 year and 4 of 7 at 2 years. Comparable differences in IgG were observed but were less often statistically significant. Despite meeting Centers for Disease Control and Prevention criteria for PPSV23 administration, almost 50% of individuals had never been vaccinated. No differences in the frequency of acute exacerbations, pneumonia, or hospitalization were observed.

CONCLUSIONS

PCV7 induces a greater functional antibody response than PPSV23 in patients with COPD that persists for 2 years after vaccination. This superior functional response supports testing of conjugate vaccination in studies examining clinical end points.

CLINICAL TRIALS REGISTRATION

NCT00457977.

Pneumococcal conjugate vaccine for adults: a new paradigm

A 13-valent pneumococcal conjugate vaccine has been studied in adults aged ≥ 50 years to compare the immune response to that induced by the 23-valent pneumococcal polysaccharide vaccine, which has been the standard of care over the past 30 years. The results demonstrate that adults, regardless of whether they are naive or previously vaccinated with the polysaccharide vaccine, have an overall superior antibody response when vaccinated with the conjugate vaccine compared with the pneumococcal polysaccharide vaccine. More importantly, the nature of the response is indicative of a T-cell-dependent response that elicits immunological memory and, therefore, primes the immune system for either natural exposure or subsequent booster vaccination with either conjugate or polysaccharide vaccine. The conjugate vaccine, which has been successful in reducing pneumococcal disease in children, now provides a new approach to preventing pneumococcal disease, including community-acquired pneumonia, in adults.

Immunosenescence and herd immunity: with an ever-increasing aging population do we need to rethink vaccine schedules?

Vaccination is a powerful public health tool that has been of tremendous benefit in protecting vulnerable populations from specific infections. Moreover, in addition to the direct benefits to vaccinated individuals, the indirect effects of protection at the community level have also been demonstrated and termed 'herd immunity'. The predicted demographic shift in the population landscape towards an ever-increasing aging population and the evidence suggesting that older individuals produce less-than-optimal vaccine responses have raised the question of rethinking vaccine schedules. This article provides evidence that even if herd immunity might be an option to indirectly protect the aging and aged adult population, the highest priorities for the near future must be to understand how vaccine responses in older individuals can be improved, to break down the public, cultural, societal and political barriers to vaccination and to counter the antivaccination movement that inhibits the worldwide spread of lifelong immunization programs.

Uptake of pneumococcal polysaccharide vaccination among working-age adults with underlying medical conditions, United States, 2009

Since 1997, the Advisory Committee on Immunization Practices has recommended the 23-valent pneumococcal polysaccharide vaccine (PPSV23) for nonelderly adults with certain medical conditions. In 2008, the Committee added asthma and cigarette smoking to the list of indications for PPSV23 vaccination. Using data from the 2009 National Health Interview Survey, the authors assessed PPSV23 uptake in people with established and new indications. To identify factors independently associated with receiving PPSV23, they used multivariable logistic regression and predictive marginal analyses. In 2009, a total of 35.2 million adults 18-64 years of age (18.6%) had established PPSV23 indications; adding asthma and smoking to the list of indications increased the high-risk population to 71.6 million people (37.9%). Overall, 26.1% of people with established indications for PPSV23 and 17.4% of people with any indication (those previously established, as well as asthma and smoking) had received the vaccine; overall coverage among persons 50-64 years of age was significantly higher than that among persons 18-49 years of age (34.6% vs. 16.7%; P < 0.001) and for all specific indications except cancer. For persons who had asthma or who smoked but had no other indications, rates of coverage were 12.3% and 8.5%, respectively. In persons who had established indications, being older, white, and unemployed and having more physician visits, a prior hospitalization, a regular physician, and health insurance were independently associated with PPSV23 receipt. PPSV23 uptake varies substantially by age and indication but remains low overall, with approximately 59 million unvaccinated high-risk working-age adults. Effective strategies to increase pneumococcal vaccination coverage among at-risk groups are needed.

Cost-effectiveness of adult vaccination strategies using pneumococcal conjugate vaccine compared with pneumococcal polysaccharide vaccine

CONTEXT

The cost-effectiveness of 13-valent pneumococcal conjugate vaccine (PCV13) compared with 23-valent pneumococcal polysaccharide vaccine (PPSV23) among US adults is unclear.

OBJECTIVE

To estimate the cost-effectiveness of PCV13 vaccination strategies in adults.

DESIGN, SETTING, AND PARTICIPANTS

A Markov state-transition model, lifetime time horizon, societal perspective. Simulations were performed in hypothetical cohorts of US 50-year-olds. Vaccination strategies and effectiveness estimates were developed by a Delphi expert panel; indirect (herd immunity) effects resulting from childhood PCV13 vaccination were extrapolated based on observed PCV7 effects. Data sources for model parameters included Centers for Disease Control and Prevention Active Bacterial Core surveillance, National Hospital Discharge Survey and Nationwide Inpatient Sample data, and the National Health Interview Survey.

MAIN OUTCOME MEASURES

Pneumococcal disease cases prevented and incremental costs per quality-adjusted life-year (QALY) gained.

RESULTS

In the base case scenario, administration of PCV13 as a substitute for PPSV23 in current recommendations (ie, vaccination at age 65 years and at younger ages if comorbidities are present) cost $28,900 per QALY gained compared with no vaccination and was more cost-effective than the currently recommended PPSV23 strategy. Routine PCV13 at ages 50 and 65 years cost $45,100 per QALY compared with PCV13 substituted in current recommendations. Adding PPSV23 at age 75 years to PCV13 at ages 50 and 65 years gained 0.00002 QALYs, costing $496,000 per QALY gained. Results were robust in sensitivity analyses and alternative scenarios, except when low PCV13 effectiveness against nonbacteremic pneumococcal pneumonia was assumed or when greater childhood vaccination indirect effects were modeled. In these cases, PPSV23 as currently recommended was favored.

CONCLUSION

Overall, PCV13 vaccination was favored compared with PPSV23, but the analysis was sensitive to assumptions about PCV13 effectiveness against nonbacteremic pneumococcal pneumonia and the magnitude of potential indirect effects from childhood PCV13 on pneumococcal serotype distribution.

Pneumococcal disease in South Australia: vaccine success but no time for complacency

BACKGROUND

Trends in age specific and serotype specific incidence rates for invasive pneumococcal disease (IPD) were examined in South Australia 4 years before and 5 years after the commencement of the Australian universal childhood 7 valent pneumococcal conjugate vaccine (7vPCV) program.

METHODS

IPD cases were identified by routine enhanced surveillance. IPD serotypes were grouped according to those covered by the 7vPCV, the six serotypes specific to the 13 valent pneumococcal conjugate vaccine (13vPCV), the 11 serotypes specific to the 23 valent pneumococcal polysaccharide vaccine (23vPPV), as well as non-13vPCV and non-23vPPV groups. Poisson regression was used to calculate age-specific and serotype-specific incident rate ratios (IRRs) comparing pre (2002-2004) and post (2007-2009) universal childhood 7vPCV periods.

RESULTS

Following the introduction of the 7vPCV program, the rate of IPD in children aged <2 years decreased by 81% for all serotypes (IRR 0.19, 95% CI, 0.13-0.28) and by 98% for 7vPCV serotypes (IRR 0.02, 95% CI, 0.007-0.07). At the same time, there was some evidence for an increase in IPD caused by 13vPCV specific serotypes (IRR 1.58, 95% CI, 0.78-3.21) and non-13vPCV serotypes (IRR 1.80, 95% CI, 0.45-7.21). Among adults aged ≥65 years, overall there was a 27% reduction in IPD caused by all serotypes following introduction of the 7vPCV program (IRR 0.73, 95% CI, 0.58-0.93). However, the rate of IPD increased in the last 2 years of the study period. The initial decrease was a result of a 74% reduction in the rate of IPD due to 7vPCV serotypes (IRR 0.26, 95% CI, 0.17-0.40). At the same time, the rate of IPD increased for 13vPCV specific serotypes (IRR 1.55, 95% CI, 0.94-2.54), 23vPPV specific serotypes (IRR 1.91, 95% CI, 0.99-3.71) and particularly non-23vPPV serotypes (IRR 5.3, 95% CI, 1.83-15.34).

CONCLUSION

There has been a large direct and sustained benefit from the universal 7vPCV program in children, particularly those aged <2 years, with some evidence for serotype replacement. There is also good evidence that the childhood program has provided indirect benefits to adults aged ≥65 years, although serotype replacement has reduced the initial benefits.

Contribution of vaccines to our understanding of pneumococcal disease

Pneumonia is the leading cause of mortality in children in developing countries and is also the leading infectious cause of death in adults. The most important cause of pneumonia is the Gram-positive bacterial pathogen, Streptococcus pneumoniae, also known as the pneumococcus. It has thus become the leading vaccine-preventable cause of death and is a successful and diverse human pathogen. The development of conjugate pneumococcal vaccines has made possible the prevention of pneumococcal disease in infants, but has also elucidated aspects of pneumococcal biology in a number of ways. Use of the vaccine as a probe has increased our understanding of the burden of pneumococcal disease in children globally. Vaccination has also elucidated the clinical spectrum of vaccine-preventable pneumococcal infections; the identification of a biological niche for multiple pneumococcal serotypes in carriage and the differential invasiveness of pneumococcal serotypes; the impact of pneumococcal transmission among children on disease burden in adults; the role of carriage as a precursor to pneumonia; the plasticity of a naturally transformable pathogen to respond to selective pressure through capsular switching and the accumulation of antibiotic-resistance determinants; and the role of pneumococcal infections in hospitalization and mortality associated with respiratory viral infections, including both seasonal and pandemic influenza. Finally, there has been a recent demonstration that pneumococcal pneumonia in children may be an important cause of hospitalization for those with underlying tuberculosis.

The potential role for protein-conjugate pneumococcal vaccine in adults: what is the supporting evidence?

Vaccination with protein-conjugate pneumococcal vaccine (PCV) provides children with extraordinary protection against pneumococcal disease, although the protective effect may be blunted by the emergence of replacement strains. Studies in adults have compared PCV with pneumococcal polysaccharide vaccine (PPV) using surrogate markers of protection, namely, serum anticapsular IgG antibody and opsonic activity. Results suggest that PCV is at least as effective as PPV for the strains covered, but a definitive and consistent advantage has not been demonstrated. Unfortunately, persons who are most in need of vaccine do not respond as well as otherwise healthy adults to either vaccine. Newer formulations of PCV will protect against the most prevalent of the current replacement strains, but replacement strains will create a moving target for PCVs. Unless an ongoing trial comparing 13-valent PCV with placebo (not to PPV) demonstrates a clearly better effect than that seen in the past with PPV, cost-effectiveness considerations are likely to prevent widespread use of PCV in adults.