Study setting
This was a multi-site community-based, randomized controlled educational intervention trial conducted at five low-income sites in Karachi. Among these, one community was urban, whereas the other four were peri-urban, located about 45 minutes travel outside of Karachi. The population in the study areas has low literacy, with only 24% of the population being literate. The total combined population of all five study sites is approximately 260,000, with high infant and maternal mortality rates. The major income generating activities include fishing and livestock rearing, or employment in local small industries (garment and leather).
The Department of Pediatrics and Child Health, Aga Khan University has well-established household-based surveillance for pregnancy and neonatal outcomes in these areas. A demographic surveillance round of the entire area is completed every three months. All pregnant women identified during this surveillance are visited frequently around the time of birth so that new births can be captured.
Eligibility and enrollment of participants
All mothers living in the study areas, and having a live child ≤ 6 weeks old, were eligible to be enrolled in the study. Twin births, infants > 6 weeks of age, or infants born to mothers living outside the study surveillance areas were excluded. The cutoff of 6 weeks was used to ensure that the intervention was implemented before the first dose of DPT/Hepatitis B came due.
Mothers of possibly eligible infants were identified through computerized surveillance databases of pregnant women and newborns maintained at each site. Families were approached with the help of local women, trained as community health workers (CHWs). The CHWs also obtained verbal consent from the mother of each eligible infant. The study protocol was approved by the Ethical Review Committee of the Aga Khan University. Informed consent was obtained from each participant at enrollment, and no breaches of confidentiality occurred.
Each mother-infant pair, who consented to participate in the study, was assigned a unique study identification number. Information on household demographics and socio-economic status was collected using a pre-tested structured questionnaire. Data collected on the infant included age, sex, place of birth, and health status. The baseline interview also recorded mother's knowledge and beliefs about vaccines. A follow-up questionnaire was used to assess the outcome. Subjects were enrolled from August 2008 to November 2008. Study participants were followed up for assessment of outcome from December 2008 to March 2009, with each individual mother-infant pair approached four months after the educational intervention session.
Randomization
Randomization lists, stratified for each of the five enrollment sites were generated by a computer and provided to the CHWs Upon consent, mother-infant pairs were assigned either to intervention or control arms through block randomization (n = 4), according to the computer-generated list. As the intervention was educational, blinding of study staff and participants was not possible. Outcome assessment was done by an investigator (BH) at each participant's house, four months after initial enrollment. The investigator was blinded to the exposure status of participants.
Intervention
To address the needs of low literacy populations, easy-to-understand pictorial cards, using very simple language, to convey three key messages as part of the educational intervention were designed. The first key message highlighted how vaccines save children's lives. The second message provided logistic information about the address and location of the local vaccination centers. The third key message emphasized the significance of retaining immunization cards, and the role they could play at the time of the child's school admissions. A copy of these pictorial messages was left with the mother. These messages took about 5 minutes to impart, and were given by the trained CHWs to each participant at their household.
The control group verbally received the general health promotion messages adapted from the curricula developed by the Pakistan Ministry of Health for the Lady Health Worker Program. These messages included information on hand-washing, breast-feeding, clean water, benefits of using oral rehydration solutions during diarrhea, bringing the infant to nearby health center when there are symptoms of acute respiratory illnesses, importance of antenatal check-ups for mothers, and some general information on vaccines. These messages were also given by trained CHWs. The length of each educational session in the control group was approximately 10-15 minutes.
Study outcome
The study outcome in each study group was the immunization status of DPT-3/Hepatitis B at 4 months after enrollment (4 to 5 months of infant's age). Immunization rates of DPT-3/Hepatitis B vaccines for intervention and control groups were assessed by an investigator, and were divided into two categories:
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1)
Infants receiving all three doses of DPT/Hepatitis B vaccines (assessed through vaccination cards) were considered "DPT-3/Hepatitis B fully immunized".
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2)
Infants missing any dose of DPT/Hepatitis B or who had lost their vaccination cards were termed"DPT-3/Hepatitis B non-immunized".
A participant was considered to be "DPT-3/Hepatitis B fully immunized" only if the mother/caretaker of the child was able to produce an EPI-issued or another health facility-issued vaccination card. Verbal responses of mothers regarding vaccine receipt without documentation on a vaccination card were not considered satisfactory evidence of their infant being fully immunized.
Sample size
We assumed a DPT-3/Hepatitis B immunization rate of 55% in the control group, and hypothesized a difference of 15% in the immunization rates between the intervention and control group. With 80% power and α = 0.05, we estimated a sample size of 163 in each arm. Adjusting for possible lost to follow-up, we enrolled 183 mother-infants pairs in each study group.
Statistical analysis
Statistical analysis was performed using SAS Version 9.2 (SAS Institute, Inc., Cary, NC). Baseline characteristics of study participants were compared using proportions. Unadjusted risk ratio (RR) and 95% confidence interval (CI) were estimated for the study outcome (DPT-3/Hepatitis B fully immunized) using bivariate Poisson regression [19, 20]. A multivariable Poisson regression model was built to assess the association between the study outcome, the study group and all other variables which were considered to be significantly associated with the study outcome at the bivariate level (p ≤ 0.20). All variables, having bivariate association with the study outcome (p ≤ 0.20) were also tested for interaction. The final model was interpreted using adjusted RR and corresponding 95% CI. The number needed to treat (NNT) in order to increase the completion of DPT-3/Hepatitis B immunization by one child was also estimated [21, 22].