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International Health

Lancet/CUGH Student Poster Winner

Michelle Mergler, MHS
PhD candidate, Global Disease Epidemiology & Control
Consortium of Universities for Global Health Student Poster Competition

Pertussis in Infants
CUGH 2014 Student Poster Competition Winner
Pertussis in Infants: Characterization of Risk and Maternal Antibody Transfer in Rural Nepal
Michelle Mergler, MHS
PhD candidate, GDEC

Pertussis in Infants: Characterization of Risk and Maternal Antibody Transfer in Rural Nepal

Pertussis is estimated to cause 2% of childhood deaths globally and is a growing public health problem in developed countries despite high DTaP vaccination coverage. Infants are at greatest risk of morbidity and mortality. Maternal vaccination during pregnancy may be effective to prevent pertussis in young infants but population-based estimates of disease burden in infants, particularly in developing countries are lacking. The effectiveness of maternal antibody transfer has also not been documented in this setting. The objective is to estimate the incidence of pertussis in infants < 6 months of age in rural southern Nepal and determine the efficiency of transfer of pertussis maternal antibody to the infants at delivery.

Nested within a larger study of maternal influenza vaccination, infants were visited weekly from birth through six months to assess respiratory illness in the prior week. If any respiratory symptoms had occurred, a nasal swab was collected and tested with a multi-target pertussis PCR assay (n=3321). Paired maternal and cord blood specimens (44 pairs) were collected and tested for antibodies to pertussis toxin (PT) using an ELISA.

The incidence of PCR-confirmed Bordetella pertussis and Bordetella parapertussis was 5.4/1000 infant years [95% CI, 2.2 -11.2] and 3.1/1000 infant years [95% CI, 0.8 - 7.9], respectively, in a cohort of 3,373 infants. Mean age of pertussis onset was 72 days and mean birth weight was 2,490 grams. There was active antibody transfer from mothers (GMT 9.75) to infants (GMT 11.25) with an overall infant/mother GMT ratio of 1.15 [95% CI, 1.04-1.28] and a correlation of specific infant/mother antibody titers of 0.96. Higher transport was seen for females and infants with longer gestation.

Population-based active home surveillance for respiratory illness found a low risk for pertussis among infants in rural Nepal. Maternal pertussis antibodies, when present, were actively transported to infants. Nepal’s immunization program, which includes a childhood whole cell pertussis vaccine, appears to be working in controlling pertussis in infants.