Invasive Pneumococcal Disease 3 Years after Introduction of 10-Valent Pneumococcal Conjugate Vaccine, the Netherlands

Response to Wu et al. - Cost-effectiveness analysis of infant pneumococcal vaccination in Malaysia and Hong Kong

A recently published paper that assessed the comparative cost-effectiveness of the 2 pneumococcal conjugate vaccines (PCVs) in Malaysia and Hong Kong reported that the 13-valent PCV vaccine (PCV13) is a better choice compared to the 10-valent pneumococcal non-typeable Haemophilus influenzae protein D conjugate vaccine (PHiD-CV or PCV10) from both a payer and societal perspective as well as under various scenarios. However, the analysis relied on a large number of assumptions that were either erroneous or did not take into account the most recent body of evidence available. A rigorous evaluation of the underlying assumptions is necessary to present a fair and balanced analysis for decision-making.

Effect of 10-valent pneumococcal conjugate vaccine on nasopharyngeal carriage of Streptococcus pneumoniae and Haemophilus influenzae among children in São Paulo, Brazil

In March 2010, Brazil introduced the 10-valent pneumococcal conjugate vaccine (PCV10) in the routine infant immunization program using a 4-dose schedule and catch-up for children <23months. We investigated PCV10 effect on nasopharyngeal carriage with vaccine-type Streptococcus pneumoniae (Spn) and non-typeable Haemophilus influenzae (NTHi) among children in São Paulo city. Cross-sectional surveys were conducted in 2010 (baseline) and 2013 (post-PCV10). Healthy PCV-naïve children aged 12-23months were recruited from primary health centers during immunization campaigns. Nasopharyngeal swabs were collected and tested for Hi; for Spn, all baseline and a stratified random sample of 400 post-PCV10 swabs were tested. We compared vaccine-type Spn and NTHi carriage prevalence pre-/post-PCV10, and used logistic regression to estimate PCV10 effectiveness (1-adjusted odds ratio×100%). Overall 501 children were included in the baseline and 1167 in the post-PCV10 survey (including 400 tested for Spn). Spn was detected in 40.3% of children at baseline and 48.8% post-PCV10; PCV10 serotypes were found in 19.8% and 1.8% respectively, representing a decline of 90.9% (p<0.0001). Carriage of vaccine-related serotypes increased (10.8-21.0%, p<0.0001), driven primarily by a rise in serotype 6C (1.8-11.2%, p<0.0001); carriage of serotypes 6A and 19A did not significantly change. PCV10 effectiveness (4 doses) against vaccine-type carriage was 97.3% (95% confidence interval 88.7-99.3). NTHi prevalence increased from 26.0% (130/501) to 43.6% (509/1167, p<0.0001); PCV10 vaccination seemed significantly associated with NTHi carriage, even after adjusting for other known risk factors. Carriage with PCV10 serotypes among toddlers declined dramatically following PCV10 introduction in São Paulo, Brazil. No protection of PCV10 against NTHi was observed. Our findings contribute to a growing body of evidence of PCV10 impact on vaccine-type carriage and highlight the importance of PCV10 as a tool to reduce the burden of pneumococcal disease in Brazil and globally.

Immunogenicity, Safety and Reactogenicity of a Booster Dose of the 10-Valent Pneumococcal Nontypeable H. influenzae Protein D Conjugate Vaccine Coadministered With DTPa-IPV-Hib in Dutch Children: A Randomized Controlled Trial

BACKGROUND

Immune responses and safety profiles may be affected when vaccines are coadministered. We evaluated the immunogenicity, safety and reactogenicity of a booster dose of the 10-valent pneumococcal nontypeable Haemophilus influenzae protein D-conjugate (PHiD-CV; Synflorix GSK Vaccines) and DTPa-IPV-Hib (Pediacel Sanofi Pasteur MSD) when coadministered.

METHODS

We performed booster assessment in a randomized controlled trial in the Netherlands. Of 780 enrolled healthy infants, 774 toddlers participated in the booster phase and received (1:1:1) (1) PHiD-CV + DTPa-HBV-IPV/Hib (Infanrix hexa, GSK Vaccines), (2) PHiD-CV + DTPa-IPV-Hib, or (3) 7-valent pneumococcal conjugate vaccine (7vCRM, Prevenar/Prevnar, Pfizer, Inc.) + DTPa-IPV-Hib at 2, 3, 4 and 11-13 months old. Blood samples were taken postprimary, prebooster, 1 and 12 months postbooster.

RESULTS

Antipneumococcal antibody responses were comparable between both PHiD-CV groups, except for serotype 18C (conjugated to tetanus toxoid). Anti-18C antibody geometric mean concentrations (GMCs) were higher when coadministered with DTPa-HBV-IPV/Hib. For each vaccine serotype, the percentages of children with antibody concentration ≥ 0.20 μg/mL were within the same ranges between PHiD-CV groups (93.8%-100%). The same was observed for the percentages of participants with opsonophagocytic activity titer ≥ 8 (90.9%-100%). When comparing both DTPa-IPV-Hib groups, postbooster antidiphtheria antibody GMCs were higher when coadministered with 7vCRM, while antitetanus and antipolyribosyl-ribitol phosphate antibody GMCs were higher with PHiD-CV coadministration. Regardless, antibody levels to these antigens were well above thresholds. Safety and reactogenicity profiles were comparable between groups.

CONCLUSIONS

Coadministration of a booster dose of PHiD-CV and DTPa-IPV-Hib was immunogenic and well tolerated.

Other age groups than children need to be considered as carriers of Streptococcal pneumoniae serotypes

We need to raise the issue that focus on children as the only carriage group for pneumococci is not optimal; we need to consider that other age groups might also be carriers of pneumococcal serotypes causing invasive pneumococcal diseases (IPD) in unvaccinated age groups. The pneumococcal conjugate vaccines (PCV) have successfully removed IPD from vaccinated children. Studies have shown an effect of PCV reducing the pneumococcal carriage of PCV serotypes in children. The status for several countries having used PCV for many years is that they do not see PCV serotypes neither carried nor as a cause of IPD in children. PCV vaccination of children has shown a herd protection effect in unvaccinated groups as a reduction in IPD cases caused by PCV serotypes. However, not all PCV serotypes have disappeared as the cause of IPD in the unvaccinated age groups. The author therefore believes that if we are to see PCV serotypes disappear as a cause of IPD in unvaccinated age groups, we need to perform further carriage studies to examine carriage in other age groups. Alternatively, all age groups should be vaccinated against pneumococci to eliminate IPD caused by PCV serotypes from possible hidden carriers.

Molecular surveillance of nasopharyngeal carriage of Streptococcus pneumoniae in children vaccinated with conjugated polysaccharide pneumococcal vaccines

Following the introduction of pneumococcal conjugate vaccines (PCVs) for infants, surveillance studies on Streptococcus pneumoniae carriage have proven valuable for monitoring vaccine effects. Here, we compared molecular versus conventional diagnostic methods in prospective cross-sectional surveillances in vaccinated infants in the Netherlands. Nasopharyngeal samples (n = 1169) from 11- and 24-month-old children, collected during autumn/winter 2010/2011 and 2012/2013, were tested by conventional culture for S. pneumoniae. DNA extracted from all culture-plate growth was tested by qPCR for pneumococcal-specific genes (lytA/piaB) and selected serotypes (including PCV13-serotypes). qPCR significantly increased the number of carriers detected compared to culture (69% vs. 57%, p < 0.0001). qPCR assays targeting vaccine-serotypes 4 and 5 proved non-specific (results excluded). For serotypes reliably targeted by qPCR, the number of serotype-carriage events detected by qPCR (n = 709) was 1.68× higher compared to culture (n = 422). There was a strong correlation (rho = 0.980; p < 0.0001) between the number of serotypes detected using qPCR and by culture. This study demonstrates the high potential of molecular methods in pneumococcal surveillances, particularly for enhanced serotype detection. We found no evidence of a hidden circulation of vaccine-targeted serotypes, despite vaccine-serotypes still significantly contributing to invasive pneumococcal disease in unvaccinated individuals, supporting the presence of a substantial S. pneumoniae reservoir outside vaccinated children.

Invasive pneumococcal disease: Clinical outcomes and patient characteristics 2-6 years after introduction of 7-valent pneumococcal conjugate vaccine compared to the pre-vaccine period, the Netherlands

BACKGROUND

Implementation of 7-valent pneumococcal conjugate vaccine (PCV7) in the Dutch national immunization program for infants led to a shift from vaccine to non-vaccine serotypes in invasive pneumococcal disease (IPD) in all age groups. We studied the impact of the serotype shift on clinical syndromes and outcomes.

METHODS

Pneumococcal isolates from hospitalized IPD patients obtained from nine sentinel microbiology laboratories, covering 25% of the Dutch population, were serotyped. Clinical syndromes, outcomes and patient characteristics in the post-PCV7 (2008-2012) period were compared with the pre-PCV7 period (2004-2006). Serotype specific propensity of the association with empyema, meningitis and death was calculated.

RESULTS

Invasive pneumonia incidence significantly decreased in children <5 years and elderly ≥65 years, but increased in 5-64 years old from 4.92 to 5.58 cases/100.000/year (RR 1.13 95% CI 0.99-1.29). Empyema incidence significantly increased in elderly 65 years and older from 0.61 to 2.60 cases/100.000/year (RR 4.28 95% CI 1.97-9.33), mainly due to serotype 1. The incidence of meningitis only declined significantly in children <5 years. IPD case-fatality decreased in children <5 years from 5% to 3%, in 5-64 years old from 9% to 7% and in elderly ≥65 years significantly from 22% to 17%, due to lower case-fatality rates for most emerging non-PCV7 serotypes.

CONCLUSIONS

An increase in empyema incidence was observed in persons ≥65 years old in the post-PCV7 era, mainly due to the emergence of serotype 1, although overall IPD case-fatality decreased. Extended conjugate vaccines that target serotype 1 or serotypes with high case-fatality may offer further reduction of pneumococcal disease burden.

Burden of four vaccine preventable diseases in older adults

BACKGROUND

Implementation of additional targeted vaccinations to prevent infectious diseases in the older adults is under discussion in different countries. When considering the added value of such preventive measures, insight into the current disease burden will assist in prioritization. The aim of this study was derive the first estimates of the disease burden in adults aged 50 years or over in the Netherlands for influenza, pertussis, pneumococcal disease and herpes zoster.

METHODS

The average annual disease burden for these four diseases in the Netherlands was calculated for the period 2010-2013 using the disability-adjusted life years (DALY) measure. Disease models and parameters were obtained from previous research. Where possible we adapted these models specifically for older adults and applied age-specific parameters derived from literature. The disease burden based on these adapted models and parameters was compared with the disease burden based on the general population models.

RESULTS

The estimated average annual disease burden was from high to low: pneumococcal disease (37,223 DALYs/year), influenza (7941 DALYs/year), herpes zoster (942 DALYs/year), and pertussis (812 DALYs/year). The adaptation of models and parameters specifically for the elderly resulted in a higher disease burden compared to the use of general population models.

CONCLUSIONS

Among older adults, the disease burden in the period 2010-2013 was highest for pneumococcal disease, mostly because of high mortality, followed by influenza. Disease burden of herpes zoster and pertussis was relatively low and consisted mostly of years lived with disability. Better information on the course of infectious diseases and long-term consequences would enable more accurate estimation of disease burden in older adults.

Nasopharyngeal carriage of Streptococcus pneumoniae and other bacteria in the 7th year after implementation of the pneumococcal conjugate vaccine in the Netherlands

After introduction of the 7-valent pneumococcal conjugate vaccine (PCV7) in the infant national immunization program (NIP) in the Netherlands in 2006, Streptococcus pneumoniae strains of the non-vaccine serotype 19A emerged and became the dominant serotype in carriage in children and their parents. Similar patterns were observed in other European countries and the United States. Increases in carriage rates of Staphylococcus aureus and non-typeable (NT) Haemophilus influenzae were also observed. After switching of PCV7 to 10-valent vaccine (PCV10) in 2011, a new carriage surveillance study was performed in the winter of 2012/2013. Nasopharyngeal carriage of S. pneumoniae, H. influenzae, S. aureus, and Moraxella catarrhalis was determined by conventional culture in 330 PCV10-vaccinated 11-month-old children, 330 PCV7-vaccinated 24-month-old children, and their parents. Carriage prevalence was compared with similar carriage studies conducted in 2005, 2009, and 2010/2011. Although serotype 19A remained the most frequently carried pneumococcal serotype in children, prevalence of 19A significantly declined in PCV7-vaccinated 24-month-old children (14% to 8%, p=0.01), but less in PCV10-vaccinated 11-month-old children (12% to 9%, p=0.31). Carriage of H. influenzae remained stable at an elevated level (65% in 11-month-olds and 69% in 24-month-olds), while the carriage of S. aureus returned to pre-PCV7 levels in 11-month-old children (14% in 2010/2011 to 7% in 2012/2013), but not in 24-month-olds (remained at 7%). Our results might indicate a new balance between replacing non-vaccine pneumococcal serotypes and other potential pathogenic bacteria in nasopharyngeal carriage. Carriage studies are valuable tools in assessing vaccine effects on pathogens circulating in the population, for evaluation of PCV impact, and in predicting changes in respiratory and invasive disease.

Risk and outcomes of invasive pneumococcal disease in adults with underlying conditions in the post-PCV7 era, The Netherlands

BACKGROUND

Immunocompromising conditions and advanced age (≥65 years) are associated with a high risk for invasive pneumococcal disease (IPD). We investigated the risk and outcomes of IPD in adults with underlying conditions in the post-PCV7 era in The Netherlands.

METHODS

IPD data from 2008 to 2012 was obtained from the national pneumococcal surveillance system, covering 25% of the Dutch population. Population estimates of underlying conditions were derived from the primary care data (2012). IPD incidence in adults with immunocompromising conditions (high risk group) and non-immunocompromising comorbidities (medium risk group) were compared to the "normal risk group" without diagnosed comorbidities. Case-fatality and ICU admission in the different risk groups was analyzed by logistic regression. Serotype specific propensities to affect high risk group IPD patients were calculated.

RESULTS

Adults with a high risk condition have a 18-fold (95% CI 15.6-21.2) and 3-fold (95% CI 2.6-3.9) higher risk compared to the normal risk group for IPD at age 18-64 years and 65 years and older, respectively. In case of a medium risk condition, the risk is 5-fold (95% CI 4.3-5.7) and 2-fold (95% CI 1.9-2.6) higher in age groups 18-64 and ≥65 years old. Likewise, IPD patients with a high or medium risk condition have a higher case-fatality (after adjustment for age, odds ratio: 2-fold (95% CI 1.5-3.5) and 1.4-fold (95% CI 1.0-2.1), respectively). Several serotypes (e.g. 6A, 6B, 23A and 23B) are associated with a significantly higher propensity to cause disease in high risk patients.

CONCLUSIONS

The risk for IPD and death in the post-PCV7 era has remained considerably high in adults and elderly with underlying conditions. The identification of serotypes with a high propensity to affect risk groups can be important for selecting (future) vaccine serotypes.