Pneumococcal carriage in households in Karonga District, Malawi, before and after introduction of 13-valent pneumococcal conjugate vaccination.

Heinsbroek, Ellen, Tafatatha, Terence, Phiri, Amos, Swarthout, Todd, Alaerts, Maaike, Crampin, Amelia C, Chisambo, Christina, Mwiba, Oddie, Read, Jonathan M and French, Neil (2018) 'Pneumococcal carriage in households in Karonga District, Malawi, before and after introduction of 13-valent pneumococcal conjugate vaccination.'. Vaccine, Vol 36, Issue 48, pp. 7369-7376.

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Abstract

BACKGROUND
Thirteen-valent pneumococcal conjugate vaccine (PCV13) was introduced in Malawi in November 2011 and is offered to infants at 6, 10 and 14 weeks of age as part of routine immunisation. PCV13 is expected to reduce vaccine type (VT) nasopharyngeal carriage, leading to reduced transmission and herd protection.

METHODS
We compared pneumococcal carriage in rural Karonga District, Malawi, pre-vaccine in 2009-2011 and post-vaccine in 2014 using a combination of cross-sectional and longitudinal analyses. Nasopharyngeal swabs were collected from a cohort of mother-infant pairs and household members <16 years. Pneumococci from 2009 to 2011 were serogrouped using latex agglutination and serotyped by Quellung reaction. In 2014, latex agglutination was used for both steps. Carriage prevalence ratios using prevalence data from before and after vaccine introduction were calculated by log-binomial regression, adjusted for age, seasonality and household composition. Participating infants in 2014 received PCV13 as part of routine immunisation.

RESULTS
VT carriage prior to PCV-13 introduction was 11.4%, 45.1%, 28.2%, 21.2% and 6.6% for 6-week old infants, 18-week old infants, children 1-4 years, children 5-15 years and mothers, respectively. After vaccine introduction, VT carriage decreased among vaccinated 18-week old infants (adjusted prevalence ratio 0.24 (95%CI 0.08-0.75)), vaccinated children 1-4 years (0.54 (0.33-0.88)), unvaccinated children 5-15 years (0.37 (0.17-0.78)) and mothers (0.34 (0.15-0.79)). No decrease in VT carriage was observed for 6-week old infants too young to be vaccinated (1.07 (0.38-3.02)) and PCV-13 ineligible children 1-4 years (0.84 (0.53-1.33)). Non-VT carriage increased only among vaccinated children 1-4 years (1.58 (1.21-2.06)).

CONCLUSIONS
There is evidence of reduced VT pneumococcal carriage three years after vaccine introduction in this rural Malawian population with good vaccine coverage using a 3 + 0 schedule. However carriage was sustained among 6-week-old infants and PCV13 ineligible 1-4 year olds, and there was some indication of serotype replacement in vaccinated 1-4 year olds.

Item Type:	Article
Subjects:	WA Public Health > Preventive Medicine > WA 115 Immunization WA Public Health > Health Problems of Special Population Groups > WA 395 Health in developing countries WC Communicable Diseases > Infection. Bacterial Infections > Bacterial Infections > WC 204 Pneumococcal pneumonia. Staphylococcal pneumonia WC Communicable Diseases > Infection. Bacterial Infections > Bacterial Infections > WC 217 Pneumococcal infections
Faculty: Department:	Clinical Sciences & International Health > Clinical Sciences Department
Digital Object Identifer (DOI):	https://doi.org/10.1016/j.vaccine.2018.10.021
Depositing User:	Stacy Murtagh
Date Deposited:	05 Nov 2018 12:14
Last Modified:	29 Nov 2018 12:04
URI:	https://archive.lstmed.ac.uk/id/eprint/9569

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