Causes of Rotavirus Vaccine Failure in Zambian Children
Zambia recently introduced routine infant immunization against rotavirus - the most important cause of severe gastroenteritis and diarrhoea mortality in children. Although vaccines like Rotarix are a cost effective tool against infectious diseases, live oral vaccines can be less immunogenic and efficacious in developing world settings as compared with industrialized countries. Reasons behind this phenomenon are not well understood, but may relate to continued maternal antigen exposure and high level maternal immunity that is passed to the foetus/newborn transplacentally and/or through breast milk.
Therefore, three arising hypotheses include: (i) high-level rotavirus-specific maternal immunity (in the form of anti-rotavirus breast-milk IgA and transplacental serum IgG) is a major contributor to failed seroconversion following infant vaccination. (ii) Malnutrition negatively impacts infant immunity and increases the risk of post-vaccination rotavirus gastroenteritis. (iii) Introduction of rotavirus vaccine will alter the molecular epidemiology of circulating rotavirus strains detected in vaccinated children presenting with severe diarrhea.
To address these hypotheses, the proposed study will recruit a prospective cohort of 420 mother-infant pairs. These will be enrolled at the time of vaccination and followed for up to four years. Baseline immunological status will be ascertained and seroconversion rates determined a month after full immunization. Incident rotavirus gastroenteritis will be monitored in the vaccinated infants whenever episodes of diarrhoea occur; through this surveillance, the sero-strains of rotaviruses causing disease will be tracked over the four year period. Contributions of HIV infection both in mothers and infants, vitamin A and zinc deficiency, weight for age Z-scores as well as mid upper arm circumference will also be assessed. Knowledge gained from this study will inform future interventional trials on strategies to improve rotavirus vaccine effectiveness in the developing world.
|Study Type:||Observational [Patient Registry]|
|Study Design:||Observational Model: Cohort
Time Perspective: Prospective
|Target Follow-Up Duration:||42 Months|
|Official Title:||An Observational Study to Evaluate Causes of Rotavirus Vaccine Failure in Zambian Children in the Context of Routine Immunization Services|
- Proportion of immunized infants exposed to high breast milk anti-rotavirus immunoglobulin-A who fail to seroconvert [ Time Frame: 1 month following full immunization ] [ Designated as safety issue: No ]
The primary exposure in this cohort is maternal IgA status, as we believe breast milk IgA is the most critical factor in failed vaccination, and maternal IgA has previously been estimated to be either high level (approximately 55%) or undetectable or low level (approximately 45%).
We will collect maternal serum and breast-milk IgA at the time of vaccination and then measure infant anti-rotavirus-specific serum IgA levels 1 month following the second dose of Rotarix™ (GlaxoSmithKline) rotavirus vaccine.
- Proportion of immunized infants exposed to transplacentally-acquired, rotavirus-specific, infant serum IgG who fail to sero-convert. [ Time Frame: 1 month after full immunisation ] [ Designated as safety issue: No ]
The co-primary exposure in this cohort is transplacentally acquired anti-rotavirus immunoglubulin-G.
We will collect infant serum at baseline before any vaccination and then measure the levels of anti-rotavirus-specific serum IgG and will also obtain the same at 1 month following the second dose of Rotarix™ rotavirus vaccine.
- Proportion of immunized infants exposed to maternal HIV infection who fail to seroconvert [ Time Frame: 1 month following full immunisation ] [ Designated as safety issue: No ]To evaluate whether maternal HIV infection (as well as level of CD4 count) affects infant vaccine take, we will collect the maternal HIV status, (and CD4 count if +ve). We will then correlate the maternal HIC status and CD4 count levels to infant zero conversion at 1 month after the two vaccine doses.
- Proportion of immunized infants with low micronutrient levels (as indicated by serum zinc and vitamin A), who fail to seroconvert [ Time Frame: 1 month after full immunization ] [ Designated as safety issue: No ]To evaluation whether nutritional status affects vaccine take, we will assess the immunized infant's nutritional status as indicated by serum level of zinc and vitamin A. These will be correlated to seroconversion results.
- Sero-epidemiology of breakthrough rotavirus infection in immunized infants [ Time Frame: 42 months ] [ Designated as safety issue: No ]
Determination of genotype in every rotavirus causing severe gastroenteritis will be done each time stool samples are collected for diarrhoea. Patients presenting with any diarrhoea will be tested for rotavirus and staged clinically (by Vesicary score). Those with severe disease (e.g., Vesikari >11/20) will be processed for genotype. Thus, we will identify the number of rotavirus cases following vaccination as well as identify the strain in those with severe disease.
This will allow for "wild type versus vaccine"strain mismatch evaluation. We anticipate that the circulating strains in the community will change in response to vaccine pressure at the population level. However, when interpreting reasons for vaccine failure, it is critically important to evaluate strain mismatch because the way to approach this type of breakthrough disease is dramatically different than if there is breakthrough infection to vaccine strain rotavirus.
Biospecimen Retention: Samples With DNA
Blood samples for immunogenicity testing will be analyzed in batches.
Stool samples for rotavirus extraction will also be stored and analyzed in batches.
|Study Start Date:||April 2013|
|Estimated Study Completion Date:||July 2017|
|Estimated Primary Completion Date:||March 2016 (Final data collection date for primary outcome measure)|
The study will involve consenting mother-infant pairs from Kamwala health facility in Lusaka where the Maternal Child Health (MCH). Those generally interested will be invited to the research clinic, where more detailed information about the study is offered. Motivated mothers will be recruited and taken through the written informed consent process by the study nurse.
Enrolled mother-infant pairs will undergo baseline procedures as earlier described. They will then be followed prospectively until about December 2016. They will be expected to come to the clinic for scheduled visits at baseline, 1, 3, 12, 15 and 42 months. They will be urged to come to the clinic for unscheduled visit should the infant be unwell at any time, and particularly each time the infant experiences diarrhoea.
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|Contact: Roma Chilengi, MD, MSc||+260973724935||Roma.Chilengi@cidrz.org|
|Contact: Bradford M Guffey, MD, MSc||+260 968666895||Brad.Guffey@cidrz.org|
|Centre for Infectious Disease Research in Zambia||Recruiting|
|Lusaka, Zambia, 10101|
|Contact: Roma Chilengi, MD, MSc +2609173724935 Roma.Chilengi@cidrz.org|
|Contact: Marcellina Hamikondo, BSc +260977120736 Marcellina.Hamikondo@cidrz.org|
|Principal Investigator: Roma Chilengi, MD, MSc|
|Principal Investigator:||Roma Chilengi, MD, MSc||Centre for Infectious Disease Research in Zambia|