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  • South Africa was the first

    2019-06-06

    South Africa was the first African country to implement the seven-valent pneumococcal conjugate vaccine (PCV7) in its routine infant immunisation programme (in 2009), with the novel schedule aligned to WHO\'s recommended Expanded Programme on Immunisation (EPI)—ie, a 2 + 1 schedule with doses at age 6, 14, and 40 weeks—with no catch-up programme for older children. The switch to the 13-valent vaccine (PCV13) in 2011 was associated with a catch-up programme for children younger than 30 months, and the coverage of three doses was estimated at 99% in 2012. After the switch from PCV7 to PCV13, the first published study from South Africa entailed national laboratory-based surveillance and showed a decline in overall cases of invasive pneumococcal disease, from 54·8 to 17·0 per 100 000 person-years for children younger than 2 years. However, a part of this decrease had been attributed to improvements in the care of people with HIV infection. In the same country, a matched case-control study from 2010 to 2012 showed effectiveness of PCV7 against invasive pneumococcal disease due to PCV7 serotypes in children without HIV infection (two or more doses of PCV7, 74% effectiveness, 95% CI 25 to 91) but not in those with HIV infection. After implementation of PCV13, population-based active surveillance of invasive pneumococcal disease in The Gambia showed a SR 3576 in the overall incidence of the disease of 55% (95% CI 30 to 71) in children younger than 2 years, owing to the striking decrease in disease caused by PCV13 serotypes (82%, 95% CI 64 to 91). 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 reduction 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.