The Lancet Global Health
Jul 2014 Volume 2 Number 7 e364 – 430
Herd protection induced by pneumococcal conjugate vaccine
Keith P Klugman
Why is herd protection from pneumococcal disease important? The pneumococcus is the leading cause of death in children worldwide,1 and children who die are likely to be those who are unable to access lifesaving antibiotics and pneumococcal conjugate vaccine (PCV). However, if vaccination of other children in the community stops transmission of the serotypes in the vaccine, then protection is provided to those most at risk of mortality, even if they are not given the vaccine themselves. The immunisation of infants with PCV in developed countries extends protection beyond direct protection of the immunised infants, to include children too young to be immunised,2 adults with substantial risk of pneumococcal disease such as those infected by HIV,3 and older people.
HPV vaccinations—possibly necessary but not sufficient
Gary M Ginsberg
Using country specific epidemiological-economic modelling, Mark Jit and colleagues1 show how the adoption of safe, well tolerated,2 immunogenic, and effective vaccination3 of 12-year-old girls against the cancer-causing human papillomaviruses (HPV)4 will prevent hundreds of thousands of cases of, and deaths from, cervical cancer worldwide.
Population effect of 10-valent pneumococcal conjugate vaccine on nasopharyngeal carriage of Streptococcus pneumoniae and non-typeable Haemophilus influenzae in Kilifi, Kenya: findings from cross-sectional carriage studies
Dr Laura L Hammitt MD a b, Donald O Akech BSc a, Susan C Morpeth FRACP a c, Angela Karani BSc a, Norbert Kihuha BSc a, Sammy Nyongesa MSc a, Tahreni Bwanaali MBA a c, Edward Mumbo BSc d, Tatu Kamau MPH e, Shahnaaz K Sharif MD e, Prof J Anthony G Scott FRCP a c f
The effect of 7-valent pneumococcal conjugate vaccine (PCV) in developed countries was enhanced by indirect protection of unvaccinated individuals, mediated by reduced nasopharyngeal carriage of vaccine-serotype pneumococci. The potential indirect protection of 10-valent PCV (PCV10) in a developing country setting is unknown. We sought to estimate the effectiveness of introduction of PCV10 in Kenya against carriage of vaccine serotypes and its effect on other bacteria.
PCV10 was introduced into the infant vaccination programme in Kenya in January, 2011, accompanied by a catch-up campaign in Kilifi County for children aged younger than 5 years. We did annual cross-sectional carriage studies among an age-stratified, random population sample in the 2 years before and 2 years after PCV10 introduction. A nasopharyngeal rayon swab specimen was collected from each participant and was processed in accordance with WHO recommendations. Prevalence ratios of carriage before and after introduction of PCV10 were calculated by log-binomial regression.
About 500 individuals were enrolled each year (total n=2031). Among children younger than 5 years, the baseline (2009—10) carriage prevalence was 34% for vaccine-serotype Streptococcus pneumoniae, 41% for non-vaccine-serotype Streptococcus pneumoniae, and 54% for non-typeable Haemophilus influenzae. After PCV10 introduction (2011—12), these percentages were 13%, 57%, and 40%, respectively. Adjusted prevalence ratios were 0•36 (95% CI 0•26—0•51), 1•37 (1•13—1•65), and 0•62 (0•52—0•75), respectively. Among individuals aged 5 years or older, the adjusted prevalence ratios for vaccine-serotype and non-vaccine-serotype S pneumoniae carriage were 0•34 (95% CI 0•18—0•62) and 1•13 (0•92—1•38), respectively. There was no change in prevalence ratio for Staphylococcus aureus (adjusted prevalence ratio for those <5 years old 1•02, 95% CI 0•52—1•99, and for those ≥5 years old 0•90, 0•60—1•35).
After programmatic use of PCV10 in Kilifi, carriage of vaccine serotypes was reduced by two-thirds both in children younger than 5 years and in older individuals. These findings suggest that PCV10 introduction in Africa will have substantial indirect effects on invasive pneumococcal disease.
GAVI Alliance and Wellcome Trust.
Cost-effectiveness of female human papillomavirus vaccination in 179 countries: a PRIME modelling study
Mark Jit PhD a b, Marc Brisson PhD c d e †, Allison Portnoy MSPH f Dr Raymond Hutubessy PhD g
Introduction of human papillomavirus (HPV) vaccination in settings with the highest burden of HPV is not universal, partly because of the absence of quantitative estimates of country-specific effects on health and economic costs. We aimed to develop and validate a simple generic model of such effects that could be used and understood in a range of settings with little external support.
We developed the Papillomavirus Rapid Interface for Modelling and Economics (PRIME) model to assess cost-effectiveness and health effects of vaccination of girls against HPV before sexual debut in terms of burden of cervical cancer and mortality. PRIME models incidence according to proposed vaccine efficacy against HPV 16/18, vaccine coverage, cervical cancer incidence and mortality, and HPV type distribution. It assumes lifelong vaccine protection and no changes to other screening programmes or vaccine uptake. We validated PRIME against existing reports of HPV vaccination cost-effectiveness, projected outcomes for 179 countries (assuming full vaccination of 12-year-old girls), and outcomes for 71 phase 2 GAVI-eligible countries (using vaccine uptake data from the GAVI Alliance). We assessed differences between countries in terms of cost-effectiveness and health effects.
In validation, PRIME reproduced cost-effectiveness conclusions for 24 of 26 countries from 17 published studies, and for all 72 countries in a published study of GAVI-eligible countries. Vaccination of a cohort of 58 million 12-year-old girls in 179 countries prevented 690 000 cases of cervical cancer and 420 000 deaths during their lifetime (mostly in low-income or middle-income countries), at a net cost of US$4 billion. HPV vaccination was very cost effective (with every disability-adjusted life-year averted costing less than the gross domestic product per head) in 156 (87%) of 179 countries. Introduction of the vaccine in countries without national HPV vaccination at present would prevent substantially more cases of cervical cancer than in countries with such programmes, although the disparity has narrowed since 2012. If 71 phase 2 GAVI-eligible countries adopt vaccination according to forecasts, then in 2070 GAVI Alliance-funded vaccination could prevent 200 000 cases of cervical cancer and 100 000 deaths in some of the highest-burden countries.
Large between-country disparities exist for HPV vaccination, with countries with the most to gain yet to introduce national HPV vaccination. Support from the GAVI Alliance could help to reduce such disparities, but a substantial burden will remain even after presently projected vaccine introductions.