Vaccine implementation reduces inequity
Authors: Asgeir Haraldsson
Journal: The Lancet Global Health (2018)

While Streptococcus pneumoniae was first described over 100 years ago, it wasn't until 50 years later that the first vaccines—pneumococcal polysaccharide vaccines at the time—were available.1Butler JC Shapiro ED Carlone GM Pneumococcal vaccines: history, current status, and future directions.Am J Med. 1999; 107: 69S-76SSummary Full Text Full Text PDF PubMed Google Scholar The use of the pneumococcal polysaccharide vaccines had an important effect on pneumococcal infections, especially in adults.1Butler JC Shapiro ED Carlone GM Pneumococcal vaccines: history, current status, and future directions.Am J Med. 1999; 107: 69S-76SSummary Full Text Full Text PDF PubMed Google Scholar However, that effect was hampered because the number of circulating serotypes was higher than initially anticipated, with about a hundred serotypes currently known.2Geno KA Gilbert GL Song JY et al.Pneumococcal capsules and their types: past, present, and future.Clin Microbiol Rev. 2015; 28: 871-899Crossref PubMed Scopus (429) Google Scholar Moreover, the effect of polysaccharide vaccines is unfortunately reduced in some target groups, particularly young children, who react poorly to polysaccharides.1Butler JC Shapiro ED Carlone GM Pneumococcal vaccines: history, current status, and future directions.Am J Med. 1999; 107: 69S-76SSummary Full Text Full Text PDF PubMed Google Scholar, 3Mehr S Wood N Streptococcus pneumoniae—a review of carriage, infection, serotype replacement and vaccination.Paediatr Respir Rev. 2012; 13: 258-264Crossref PubMed Scopus (99) Google Scholar, 4Bogaert D de Groot R Hermans PWM Streptococcus pneumoniae colonisation: the key to pneumococcal disease.Lancet Infect Dis. 2004; 4: 144-154Summary Full Text Full Text PDF PubMed Scopus (1394) Google Scholar In the 1990s and early 2000s, pneumococcal conjugate vaccines (PCV) emerged.1Butler JC Shapiro ED Carlone GM Pneumococcal vaccines: history, current status, and future directions.Am J Med. 1999; 107: 69S-76SSummary Full Text Full Text PDF PubMed Google Scholar, 4Bogaert D de Groot R Hermans PWM Streptococcus pneumoniae colonisation: the key to pneumococcal disease.Lancet Infect Dis. 2004; 4: 144-154Summary Full Text Full Text PDF PubMed Scopus (1394) Google Scholar By conjugating proteins to the different capsular polysaccharides, a T-cell immune reaction is elicited, resulting in sufficient immune response in children. However, the number of serotypes that can be conjugated to the capsular polysaccharides is limited in the available formulations. The initial seven-valent vaccine was later replaced with higher valent vaccines. The effects of PCVs, especially higher valent PCVs, on invasive pneumococcal disease,3Mehr S Wood N Streptococcus pneumoniae—a review of carriage, infection, serotype replacement and vaccination.Paediatr Respir Rev. 2012; 13: 258-264Crossref PubMed Scopus (99) Google Scholar, 5Fitzwater SP Chandran A Santosham M Johnson HL The worldwide impact of the seven-valent pneumococcal conjugate vaccine.Pediatr Infect Dis J. 2012; 31: 501-508Crossref PubMed Scopus (152) Google Scholar, 6Simell B Auranen K Kayhty H Goldblatt D Dagan R O'Brien KL The fundamental link between pneumococcal carriage and disease.Expert Rev Vaccines. 2012; 11: 841-855Crossref PubMed Scopus (433) Google Scholar respiratory infections,5Fitzwater SP Chandran A Santosham M Johnson HL The worldwide impact of the seven-valent pneumococcal conjugate vaccine.Pediatr Infect Dis J. 2012; 31: 501-508Crossref PubMed Scopus (152) Google Scholar, 7Palmu AA Rinta-Kokko H Nohynek H Nuorti JP Kilpi TM Jokinen J Impact of ten-valent pneumococcal conjugate vaccine on pneumonia in Finnish children in a nation-wide population-based study.PLoS One. 2017; 12: e0172690Crossref PubMed Scopus (35) Google Scholar nasopharyngeal carriage,6Simell B Auranen K Kayhty H Goldblatt D Dagan R O'Brien KL The fundamental link between pneumococcal carriage and disease.Expert Rev Vaccines. 2012; 11: 841-855Crossref PubMed Scopus (433) Google Scholar, 8Sigurdsson S Erlendsdottir H Quirk SJ et al.Pneumococcal vaccination: direct and herd effect on carriage of vaccine types and antibiotic resistance in Icelandic children.Vaccine. 2017; 35: 5242-5248Crossref PubMed Scopus (32) Google Scholar and acute otitis media5Fitzwater SP Chandran A Santosham M Johnson HL The worldwide impact of the seven-valent pneumococcal conjugate vaccine.Pediatr Infect Dis J. 2012; 31: 501-508Crossref PubMed Scopus (152) Google Scholar, 9Sigurdsson S Eythorsson E Hrafnkelsson B Erlendsdottir H Kristinsson KG Haraldsson A Reduction in all-cause acute otitis media in children <3 years of age in primary care following vaccination with 10-valent pneumococcal haemophilus influenzae protein-D conjugate vaccine: a whole-population study.Clin Infect Dis. 2018; 67: 1213-1219Crossref PubMed Scopus (27) Google Scholar have been widely published and are indisputable.4Bogaert D de Groot R Hermans PWM Streptococcus pneumoniae colonisation: the key to pneumococcal disease.Lancet Infect Dis. 2004; 4: 144-154Summary Full Text Full Text PDF PubMed Scopus (1394) Google Scholar Nevertheless, the global burden of disease of pneumococcal infections is still enormous, with a high annual global mortality, especially in children in lower-income countries.1Butler JC Shapiro ED Carlone GM Pneumococcal vaccines: history, current status, and future directions.Am J Med. 1999; 107: 69S-76SSummary Full Text Full Text PDF PubMed Google Scholar, 6Simell B Auranen K Kayhty H Goldblatt D Dagan R O'Brien KL The fundamental link between pneumococcal carriage and disease.Expert Rev Vaccines. 2012; 11: 841-855Crossref PubMed Scopus (433) Google Scholar Nasopharyngeal carriage is thought to be a prerequisite for clinically symptomatic pneumococcal infections and carriage rates are especially high in young children.3Mehr S Wood N Streptococcus pneumoniae—a review of carriage, infection, serotype replacement and vaccination.Paediatr Respir Rev. 2012; 13: 258-264Crossref PubMed Scopus (99) Google Scholar, 4Bogaert D de Groot R Hermans PWM Streptococcus pneumoniae colonisation: the key to pneumococcal disease.Lancet Infect Dis. 2004; 4: 144-154Summary Full Text Full Text PDF PubMed Scopus (1394) Google Scholar, 6Simell B Auranen K Kayhty H Goldblatt D Dagan R O'Brien KL The fundamental link between pneumococcal carriage and disease.Expert Rev Vaccines. 2012; 11: 841-855Crossref PubMed Scopus (433) Google Scholar, 8Sigurdsson S Erlendsdottir H Quirk SJ et al.Pneumococcal vaccination: direct and herd effect on carriage of vaccine types and antibiotic resistance in Icelandic children.Vaccine. 2017; 35: 5242-5248Crossref PubMed Scopus (32) Google Scholar Therefore, studying pneumococcal nasopharyngeal carriage can give important information on circulating serotypes in the community, potential invasiveness, and microbial resistance patterns.4Bogaert D de Groot R Hermans PWM Streptococcus pneumoniae colonisation: the key to pneumococcal disease.Lancet Infect Dis. 2004; 4: 144-154Summary Full Text Full Text PDF PubMed Scopus (1394) Google Scholar, 6Simell B Auranen K Kayhty H Goldblatt D Dagan R O'Brien KL The fundamental link between pneumococcal carriage and disease.Expert Rev Vaccines. 2012; 11: 841-855Crossref PubMed Scopus (433) Google Scholar PCVs have a clear effect on the nasopharyngeal carriage, with a decrease of horizontal spread and a distinct reduction in vaccine-serotype pneumococci.6Simell B Auranen K Kayhty H Goldblatt D Dagan R O'Brien KL The fundamental link between pneumococcal carriage and disease.Expert Rev Vaccines. 2012; 11: 841-855Crossref PubMed Scopus (433) Google Scholar, 8Sigurdsson S Erlendsdottir H Quirk SJ et al.Pneumococcal vaccination: direct and herd effect on carriage of vaccine types and antibiotic resistance in Icelandic children.Vaccine. 2017; 35: 5242-5248Crossref PubMed Scopus (32) Google Scholar This decrease in horizontal spread can also lead to an increased herd effect, which adds to the primary effect of the vaccines. However, despite the effects on vaccine-serotype pneumococci, the total pneumococcal carriage rates are either not affected or marginally affected, as vaccine-serotype pneumococci are replaced by non-vaccine serotypes.2Geno KA Gilbert GL Song JY et al.Pneumococcal capsules and their types: past, present, and future.Clin Microbiol Rev. 2015; 28: 871-899Crossref PubMed Scopus (429) Google Scholar, 3Mehr S Wood N Streptococcus pneumoniae—a review of carriage, infection, serotype replacement and vaccination.Paediatr Respir Rev. 2012; 13: 258-264Crossref PubMed Scopus (99) Google Scholar, 4Bogaert D de Groot R Hermans PWM Streptococcus pneumoniae colonisation: the key to pneumococcal disease.Lancet Infect Dis. 2004; 4: 144-154Summary Full Text Full Text PDF PubMed Scopus (1394) Google Scholar, 5Fitzwater SP Chandran A Santosham M Johnson HL The worldwide impact of the seven-valent pneumococcal conjugate vaccine.Pediatr Infect Dis J. 2012; 31: 501-508Crossref PubMed Scopus (152) Google Scholar As long as these non-vaccine serotypes colonising the nasopharynx are less invasive, cause less pneumococcal infections, and are susceptible to antibiotics, the overall effects of the vaccine programmes should be regarded as extremely successful. Nevertheless, it is obviously important to closely monitor any changes in the nasopharyngeal carriage of pneumococcal serotypes because new serotypes, possibly invasive and antibiotic resistant, might emerge and pose a threat for clinically significant infections in the future.4Bogaert D de Groot R Hermans PWM Streptococcus pneumoniae colonisation: the key to pneumococcal disease.Lancet Infect Dis. 2004; 4: 144-154Summary Full Text Full Text PDF PubMed Scopus (1394) Google Scholar, 6Simell B Auranen K Kayhty H Goldblatt D Dagan R O'Brien KL The fundamental link between pneumococcal carriage and disease.Expert Rev Vaccines. 2012; 11: 841-855Crossref PubMed Scopus (433) Google Scholar In the Lancet Global Health, Eileen M Dunne and colleagues10Dunne EM Satzke C Ratu FT et al.Effect of ten-valent pneumococcal conjugate vaccine introduction on pneumococcal carriage in Fiji: results from four annual cross-sectional carriage surveys.Lancet Glob Health. 2018; 6: e1375-e1385Summary Full Text Full Text PDF PubMed Scopus (40) Google Scholar report the results of four annual carriage surveys in Fiji on the effect of ten-valent PCV introduction in Fiji. They described a decline in adjusted prevalences (2015 vs 2012) in pneumococcal nasopharyngeal carriage of vaccine serotypes in 5–8-week-old infants (0·56, 95% CI 0·34–0·93), 12–23-month-old children (0·34, 0·23–0·49), 2–6-year-old children (0·47, 0·34–0·66), and their caregivers (0·43, 0·13–1·42) 3 years after PCV introduction. These results support a strong herd protection in the community, as evident in the carriage decline described in infants too young to be vaccinated. This important finding adds to earlier publications on the herd effect of PCV, in both children and older populations.5Fitzwater SP Chandran A Santosham M Johnson HL The worldwide impact of the seven-valent pneumococcal conjugate vaccine.Pediatr Infect Dis J. 2012; 31: 501-508Crossref PubMed Scopus (152) Google Scholar, 7Palmu AA Rinta-Kokko H Nohynek H Nuorti JP Kilpi TM Jokinen J Impact of ten-valent pneumococcal conjugate vaccine on pneumonia in Finnish children in a nation-wide population-based study.PLoS One. 2017; 12: e0172690Crossref PubMed Scopus (35) Google Scholar, 8Sigurdsson S Erlendsdottir H Quirk SJ et al.Pneumococcal vaccination: direct and herd effect on carriage of vaccine types and antibiotic resistance in Icelandic children.Vaccine. 2017; 35: 5242-5248Crossref PubMed Scopus (32) Google Scholar An important message of the study by Dunne and colleagues is the unambiguous effect of PCV introduction on carriage of vaccine serotypes on both the Indigenous population and the population of Indian descent in Fiji. It is well described that the rate of pneumococcal nasopharyngeal carriage is different in various populations and age groups, often high in Indigenous populations, low-income communities, crowed households, and low socioeconomic status.3Mehr S Wood N Streptococcus pneumoniae—a review of carriage, infection, serotype replacement and vaccination.Paediatr Respir Rev. 2012; 13: 258-264Crossref PubMed Scopus (99) Google Scholar, 4Bogaert D de Groot R Hermans PWM Streptococcus pneumoniae colonisation: the key to pneumococcal disease.Lancet Infect Dis. 2004; 4: 144-154Summary Full Text Full Text PDF PubMed Scopus (1394) Google Scholar, 8Sigurdsson S Erlendsdottir H Quirk SJ et al.Pneumococcal vaccination: direct and herd effect on carriage of vaccine types and antibiotic resistance in Icelandic children.Vaccine. 2017; 35: 5242-5248Crossref PubMed Scopus (32) Google Scholar This translates into higher risk of infections caused by pneumococcus in these groups, adding to this inequity. This study from Fiji reiterates the knowledge that initiating vaccination programmes can not only decrease severe infections, but also reduce inequity and disparity. That is important! I report grants from Landspitali University Hospital Research Fund and GlaxoSmithKline, outside the submitted work; I was part of a 2018 advisory group for GlaxoSmithKline. Effect of ten-valent pneumococcal conjugate vaccine introduction on pneumococcal carriage in Fiji: results from four annual cross-sectional carriage surveysDirect and indirect effects on pneumococcal carriage post-PCV10 are likely to result in reductions in pneumococcal disease, including in infants too young to be vaccinated. Serotype replacement in carriage in Fijian children, particularly Indigenous children, warrants further monitoring. Observed changes in pneumococcal density might be temporal rather than vaccine related. Full-Text PDF Open Access