Streptococcus pneumoniae and other bacterial nasopharyngeal colonization seven years post-introduction of 13-valent pneumococcal conjugate vaccine in South African children

Abstract

Listen

Translate article

Pneumococcal Conjugate Vaccines (PCVs) reduce pneumococcal-associated disease by reducing vaccine-serotype (VT) acquisition in vaccinated children, thereby interrupting VT transmission. The 7-valent-PCV was introduced in the South African immunisation program since 2009 (13-valent-PCV since 2011) using a 2+1 schedule (6-, 14- and 40-weeks age). We aimed to evaluate temporal changes in VT and non-vaccine-serotype (NVT) colonisation after nine years of childhood PCV immunisation in South Africa. Nasopharyngeal swabs were collected from healthy children <60-months-old (n=571) in 2018 (Period-2) and compared with samples (n=1135) collected during early PCV7-introduction (Period-1, 2010-11) in an urban low-income setting (Soweto). Pneumococci were tested for using a multiplex quantitative-PCR serotyping reaction-set. Overall pneumococcal colonisation in Period-2 (49.4%; 282/571) was 27.5% lower than Period-1 (68.1%; 773/1135; aOR:0.66; 95%CI:0.54-0.88). Colonisation by VT was reduced by 54.5% in Period-2 (18.6%; 106/571) compared with Period-1 (40.9%; 465/1135; aOR:0.41; 95%CI:0.3-0.56). Nevertheless, serotype 19F carriage prevalence was higher (8.1%; 46/571) in Period-2 compared with Period-1 (6.6%; 75/1135; aOR:2.0; 95%CI:1.09-3.56). NVT colonisation prevalence was similar in Period-2 and Period-1 (37.8%; 216/571 and 42.4%; 481/1135). There remains a high residual prevalence of VT, particularly 19F, colonisation nine years post introduction of PCV in the South African childhood immunisation program.