Indirect Effects of 10-Valent Pneumococcal Conjugate Vaccine Against Adult Pneumococcal Pneumonia in Rural Western Kenya

Abstract

Background: Data on pneumococcal conjugate vaccine (PCV) indirect effects in low-income countries with high HIV burden are limited. We examined adult pneumococcal pneumonia incidence before and after 10-valent PCV introduction in Kenya in 2011. Methods: From 1/1/2008 to 12/31/2016, we conducted surveillance for acute respiratory infection (ARI) among ~12,000 adults (≥18 years) in western Kenya, where HIV prevalence ~17%. ARI cases (cough or difficulty breathing or chest pain, plus temperature ≥38.0◦C or oxygen saturation <90%) presenting to a clinic underwent blood culture and pneumococcal urine antigen testing (UAT). We calculated ARI incidence and adjusted for healthcare seeking using data from household visits. The proportion of ARI cases with pneumococcus detected among those with complete testing (blood culture and UAT) was multiplied by adjusted ARI incidence to estimate pneumococcal pneumonia incidence. Results: Pre-PCV (2008–2010), crude and adjusted ARI incidence were 3.14 and 5.30/100 person-years-observation (pyo), respectively. Among ARI cases, 39.0% (340/872) had both blood culture and UAT; 21.2% (72/340) had pneumococcus detected, yielding baseline pneumococcal pneumonia incidence of 1.12/100 pyo (95% confidence interval [CI] 1.0–1.3). In each post-PCV year (2012–2016), pneumococcal pneumonia incidence was significantly lower than baseline; with incidence rate ratios (IRR) of 0.53 (95%CI 0.31–0.61) in 2012 and 0.13 (95%CI 0.09–0.17) in 2016. Similar declines were observed in HIV-infected (IRR 0.13, 95%CI 0.08–0.22), and HIV-uninfected (IRR 0.10, 95%CI 0.05–0.20). Conclusions: Adult pneumococcal pneumonia declined in western Kenya following 10-valent PCV introduction, likely reflecting vaccine indirect effects. Evidence of herd protection is critical for guiding PCV policy decisions in resource-constrained areas.

Vaccine strategies to reduce the burden of pneumococcal disease in HIV-infected adults in Africa.

“…Although ART has reduced the risk of IPD and subsequent mortality [ 3 , 40 ], the risk remains more than 30-fold higher than in HIV-uninfected adults [ 41 ] with an incidence of >50 cases per 100,000 person years [ 3 , 5 , 42 ]. The introduction of infant PCV programs in South Africa and Kenya has led to a further reduction in VT-IPD and pneumococcal pneumonia incidence in HIV-infected adults [ 9 , 43 , 44 ].…”

Evaluation of the impact of childhood 13-valent pneumococcal conjugate vaccine introduction on adult pneumonia in Ulaanbaatar, Mongolia: study protocol for an observational study

“…Previous studies have shown increases over time in the indirect effect of childhood vaccination with PCV7 and PCV13 on adult invasive pneumococcal disease [54] and pneumonia [15]. Indirect impact is not only related to time since vaccine introduction, but it is also affected by other factors such as vaccine coverage and timing.…”

“…For example, there is more frequent pneumococcal carriage in low-and middle-income countries with horizontal transmission between children and adults; developing country PCV schedules often do not include a post infancy booster dose (which may be critical to reductions in transmission) [10]; crowding and other factors may influence carriage density [11,12]; indoor and outdoor pollution may damage upper airway mucosa [13] which may also then influence pneumococcal carriage; and transmission pathways may differ by geography such as the potential for serotype 1 transmission outside of early childhood in the African meningitis belt [14]. One of the few studies in a resource poor setting [15] from Kenyareported a 47 to 94% reduction in adult pneumococcal pneumonia incidence following the introduction of the 10-valent PCV using a 3 + 0 schedule (6,10 and 14 weeks) in the childhood immunisation programme. Even though other improvements in healthcare may have contributed to the decline, the authors argued that the indirect PCV effect could have a considerable effect on adult disease in a high burden setting [15].…”

“…One of the few studies in a resource poor setting [15] from Kenyareported a 47 to 94% reduction in adult pneumococcal pneumonia incidence following the introduction of the 10-valent PCV using a 3 + 0 schedule (6,10 and 14 weeks) in the childhood immunisation programme. Even though other improvements in healthcare may have contributed to the decline, the authors argued that the indirect PCV effect could have a considerable effect on adult disease in a high burden setting [15]. While encouraging, these data need to be replicated in other settings.…”

The Epidemiological and Financial Effects of Pneumococcal Vaccination on Otitis Media Related Admissions in the United States

“…The PCV7 vaccine had caused a “replacement phenomena” in the serotypes causing disease. 4,5 Non-PCV7 serotype 19A became a major cause of severe AOM with high complication rates of mastoiditis, subperiosteal abscesses, and mastoidectomies due to its increased virulence and antibiotic resistance. 6,7 Due to the replacement phenomenon, as well as the severity of serotype 19A infection, PCV13 was released in 2010 with additional serotypes, including 19A.…”