Epidemiology of Serotype 1 Invasive Pneumococcal Disease, South Africa, 2003–2013

Streptococcus pneumoniae serotype 1 is highly invasive and rarely carried asymptomatically (1). The incidence of serotype 1 invasive pneumococcal disease (IPD) fluctuates year to year; disease is associated with outbreaks in closed communities and hospitals and, in Africa, with communitywide meningitis outbreaks (2). Compared with other S. pneumoniae serotypes, serotype 1 tends to cause fewer cases of fatal disease, and antibiotic-resistant cases are unusual (1). IPD is common in children with underlying diseases, especially HIV. A study conducted among children 18 months of age (11,12). In South Africa, PCV7 was introduced into the national immunization schedule in April 2009 as a 3-dose regimen for infants 6 weeks, 14 weeks, and 9 months of age; in April 2011, the vaccine was replaced with PCV13. Among children <1 year of age, reported coverage for the third dose of PCV improved from 10% in 2009 to 81% in 2012 but declined to 62% in 2013 (13). In 2012, after PCV13 introduction, serotype 1 IPD incidence showed a temporally associated decline in children <2 years of age (−57%, 95% CI −79% to −16%) and adults 25–44 years of age (−33%, 95% CI −46% to −17%) compared with incidence in 2005–2008 (14). Information regarding S. pneumoniae serotype 1 epidemiology in Africa is limited. We compared serotype 1 disease epidemiology in South Africa with that of other serotypes over an 11-year period, before and after introduction of PCV7 and PCV13. We also explored whether temporal or spatial clusters of serotype 1 disease occurred during the study period.