The effectiveness of PCV and PCV in high income countries

The effectiveness of PCV7 and PCV13 in high-income countries has been well documented, with two case-control studies of PCV13 effectiveness done in the USA and the UK. However, the effectiveness reported in high-income countries is not automatically transposable to countries of low and middle income: the proportion of serotypes covered by pneumococcal conjugate vaccines could be different, as could the serotype replacement. Few studies have been done in low-income and middle-income countries, particularly in Africa. In , Cheryl Cohen and colleagues present findings of a case-control study from South Africa of PCV13 effectiveness against invasive pneumococcal disease in children not infected with HIV and in those with HIV infection, from 2012 to 2014. Cohen and colleagues found the 2 + 1 schedule effective for preventing invasive pneumococcal disease caused by PCV13 serotypes in children without HIV infection (two or more doses of PCV13, 85% effectiveness, 95% CI 37 to 96). However, PCV13 was not effective for overall invasive pneumococcal disease in children not infected with HIV (52%, 95% CI −12 to 79) nor for PCV13-serotype invasive pneumococcal disease in children with HIV infection (91%, −35 to 100). The findings of Cohen and colleagues fit with those of current international studies of the effect of PCV13, confirming the great efficacy of PCV13 against pneumococcal disease caused by PCV13 serotypes. One concern draws our attention: the difference in distribution of non-vaccine serotypes in children not infected with HIV versus those with HIV infection. In children not infected with HIV, the main non-vaccine serotypes were 15B/C, 12F, 35B, and 8, and in those with HIV infection, the primary non-vaccine serotype was 16F. has more than 95 serotypes; each can presumably cause pneumococcal disease, and nasopharyngeal colonisation is the precursor of invasive and mucosal pneumococcal diesase. The effectiveness of pneumococcal conjugate vaccines against vaccine-type pneumococcal disease and carriage was shown with the same range of intensity in many countries, although, overall, pneumococcal carriage decreased only slightly and the replacement was almost complete. By contrast, worldwide, implementation of pneumococcal conjugate vaccines has resulted in a TASIN-1 Supplier in overall incidence of pneumococcal disease. However, because serotypes do not have the same disease potential, the magnitude of the overall decline in invasive pneumococcal disease has differed depending on the country and population. Many of the emerging non-vaccine serotypes in carriage after PCV13 implementation (11A, 15B/C, 15A, 21, 23B, and 35F) show low potential for causing invasive disease, but some—eg, 12F, 22F, 24F, 8, and 9N—have high disease potential. Moreover, in vulnerable populations (eg, immunocompromised people), serotypes with low disease potential could induce severe invasive pneumococcal disease. Changes in serotype distribution have resulted in changes in the profile and spectrum of pneumococcal disease (eg, in the proportion of meningitis, bacteraemic pneumonia, and bacteraemia without focus) and an increase in the proportion of patients with underlying conditions who are easily infected by non-vaccine serotypes. Not surprisingly, in the study by Cohen and colleagues, 26% of children with invasive pneumococcal disease who were not infected with HIV had an underlying condition. The study by Cohen and colleagues probably underestimates the effectiveness of PCV13 not only because case-control studies ignore the herd effect but also because of the use of small sample sizes, as the authors underline. The new data from South Africa and The Gambia show a high degree of effectiveness of pneumococcal conjugate vaccine, comparable with that seen in high-income countries, and should encourage countries that have not yet incorporated pneumococcal conjugate vaccines into their national immunisation programmes to do so. Assessing the effect of pneumococcal conjugate vaccines should be multifaceted (invasive pneumococcal disease, pneumonia, nasopharyngeal flora) and continual because of the permanent adaptation of pneumococcus to escape external pressures such as vaccination and antibiotics.
On Jan 31, 2017, heads of states and governments of the African Union and the leadership of the African Union Commission will officially launch the Africa Centres for Disease Control and Prevention (Africa CDC) in Addis Ababa, Ethiopia. As detailed in the African Union\'s Africa Agenda 2063—a roadmap for the development of the continent—some of the concerns that justified the establishment and initiation of an Africa-wide public health agency include rapid population growth; increasing and intensive population movement across Africa, with increased potential for new or re-emerging pathogens to turn into pandemics; existing endemic and emerging infectious diseases, including Ebola; antimicrobial resistance; increasing incidence of non-communicable diseases and injuries; high maternal mortality rates; and threats posed by environmental toxins. In addition to these concerns, African countries are burdened with insufficient public health assets including surveillance, laboratory networks, competent workforce, and research expertise that hinder evidence-based decision-making.