Maternal pneumococcal nasopharyngeal carriage and risk factors for neonatal carriage after the introduction of pneumococcal conjugate vaccines in The Gambia

Abstract

Objectives: Pneumococcal nasopharyngeal carriage occurs early in life. However, the role of vertical transmission is not well understood. The aims of this study were to describe carriage among mothers and their newborns, and to assess for risk factors for neonatal carriage. Methods: In a nested retrospective cohort study, we analysed data from the control arm of a randomized controlled trial conducted in The Gambia 2 to 3 years after introduction of pneumococcal conjugate vaccine (PCV) 13. Nasopharyngeal swabs were collected from 374 women and their newborns on the day of delivery, then 3, 6, 14 and 28 days later. Pneumococci were isolated and serotyped using conventional microbiologic methods. Results: Carriage increased from 0.3% (1/373) at birth to 37.2% (139/374) at day 28 (p <0.001) among neonates and from 17.1% (64/374) to 24.3% (91/374) (p 0.015) among women. In both groups, PCV13 vaccine-type (VT) serotypes accounted for approximately one-third of the pneumococcal isolates, with serotype 19A being the most common VT. Maternal carriage (adjusted odds ratio (OR) ¼ 2.82; 95% confidence interval (CI), 1.77e4.80), living with other children in the household (adjusted OR ¼ 4.06; 95% CI, 1.90e8.86) and dry season (OR ¼ 1.98; 95% CI, 1.15e3.43) were risk factors for neonatal carriage. Over half (62.6%) of the neonatal carriage was attributable to living with other children in the same household. Conclusions: Three years after the introduction of PCV in The Gambia, newborns are still rapidly colonized with pneumococcus, including PCV13 VT. Current strategies for pneumococcal control in Africa do not protect this age group beyond the herd effect.

Persistence of Nasopharyngeal Pneumococcal Vaccine Serotypes and Increase of Nonvaccine Serotypes Among Vaccinated Infants and Their Mothers 5 Years After Introduction of Pneumococcal Conjugate Vaccine 13 in The Gambia

“…Although the direct effect of PCV13 on circulating PCV13 VTs among vaccinated infants was observed 1 year after its introduction (CSS2) [16], 5 years later (CSS3) VTs were still circulating in infants who had received 3 doses of the vaccine. The PCV13 VT prevalence in this study (11.4%) is similar to VT carriage among Gambian newborns 2 years after routine PCV13 [27] but 2-fold higher than PCV13 VT prevalence in Greenlandic children <5 years old (5%) 3 years after PCV13 [28], Belgian children (5.4%) 5 years after PCV13 and 9 years after PCV7 [29], and Australian aboriginal children <5 years old (5.8%) 3 years after PCV13 and 10 years after PCV7 [30]. We saw a significant increase in serotype 19F after PCV13 introduction which was also among the most common VTs after PCV13 in the Belgian study [29].…”

“…In CSS3, we detected a significant increase in serotypes 21 and 23B. These were also the most prevalent serotypes in the post-PCV13 era in studies conducted in The Gambia [27], Italy, and Norway [39, 40]. Unexpectedly, among mothers the increase in NVTs exceeded the decrease in VTs, resulting in an overall increase in carriage.…”

Impact of PCV7 vaccination on nasopharyngeal carriage and antimicrobial resistance among children in Turkey

“…However, we regarded the vaccination of children as the most important factor, although we found that household crowding and having siblings over the age of five were independent risk factors for nasopharyngeal carriage. This association has been observed in other studies [15]. If the siblings had been vaccinated with PCV7, this might not have been a risk factor for nasopharyngeal carriage, but the history of PCV7 vaccination for the siblings of infants was not collected in the current study.…”

High rate of antibiotic resistance among pneumococci carried by healthy children in the eastern part of the Democratic Republic of the Congo

“…By using culture for pneumococcal detection, we found that the prevalence of nasopharyngeal carriage was 21%. Generally higher levels of carriage have been reported from several other African countries, but there is also a great deal of variation between different regions [ 21 , 32 – 35 ].…”