A variety of studies have considered the affects of India's son preference on gender differences in child mortality, sex ratio at birth, and access to health services. Less research has focused on the affects of son preference on gender inequities in immunization coverage and how this may have varied with time, and across regions and with sibling compositions. We present a systematic examination of trends in immunization coverage in India, with a focus on inequities in coverage by gender, birth order, year of birth, and state.
We analyzed data from three consecutive rounds of the Indian National Family Health Survey undertaken between 1992 and 2006. All children below five years of age with complete immunization histories were included in the analysis. Age-appropriate immunization coverage was determined for the following antigens: bacille Calmette-Guérin (BCG), oral polio (OPV), diphtheria, pertussis (whooping cough) and tetanus (DPT), and measles.
Immunization coverage in India has increased since the early 1990s, but complete, age-appropriate coverage is still under 50% nationally. Girls were found to have significantly lower immunization coverage (p<0.001) than boys for BCG, DPT, and measles across all three surveys. By contrast, improved coverage of OPV suggests a narrowing of the gender differences in recent years. Girls with a surviving older sister were less likely to be immunized compared to boys, and a large proportion of all children were found to be immunized considerably later than recommended.
Gender inequities in immunization coverage are prevalent in India. The low immunization coverage, the late immunization trends and the gender differences in coverage identified in our study suggest that risks of child mortality, especially for girls at higher birth orders, need to be addressed both socially and programmatically.
Abstract in Hindi
See the full article online for a translation of this abstract in Hindi.
Abstract in Hindi
See Additional file 1 for a translation of the abstract to this article in Hindi.
In India there is a well-documented history of son preference [1-4]. A growing body of literature has examined the impacts of India's son preference on child survival, juvenile sex ratio, and the numbers of "missing" women [5-10]. There is evidence that the son preference in India and other South Asian countries contributes to disadvantage in women's health throughout the life course . Disadvantage for girls in India begins with a reduced chance of being born at all, and those who are born face lower access to preventive care and treatment of disease compared to boys [6,11,12].
Girls born in India have a 40% greater risk of ill health compared to boys and are less likely to access health care, in particular immunization [11,13,14]. Boys, however, are more likely than girls to die in the first month of life from perinatal conditions, such as birth asphyxia and birth trauma. Only two other conditions (unintentional injuries and congenital anomalies) are more common among boys than girls. Beyond these causes, and contrary to the trends observed in most of the world, in India more girls than boys die of acute respiratory diseases, infectious and parasitic diseases, and viral infections [15,16].
Many of the deaths among India's children are avoidable, including those from the childhood cluster of vaccine preventable diseases (especially measles and tetanus), malaria, diarrhoea caused by organisms such as rotavirus, and acute respiratory infections caused by Streptococcus pneumonia and HÃ¦mophilus influenza type b (HiB). Recent data shows that immunization - long established worldwide as a highly cost-effective lifesaver - still reaches only a minority of India's children, even after the substantial improvements in vaccination coverage against measles and polio. To make matters worse, girls are especially vulnerable due to inequities in access to immunization coverage .
Preference for sons in India has been noted to vary across regions, levels of fertility, and order of birth [1,18-20]. A wide variety of studies have examined the affects of India's son preference on child mortality and India's sex ratio in light of changing fertility patterns and concern for "missing" women. Less research has focused on the influence of India's son preference on gender inequities in access to health care, specifically immunization, and how this may have varied with time and across regions. In this article we investigate the presence of gender inequities in terms of access to timely immunization coverage. We will focus on trends in gender inequities at the national level, by birth order, and by state of residence using data collected from 1992 to 2006.
Inequities in immunization coverage by gender have been shown to exist throughout India . Of the 17 major states, 10 have demonstrated inequity in full immunization coverage against girls. Even states that perform well in immunization coverage struggle with considerably different immunization rates between boys and girls . A search of available literature yielded several studies reporting lower immunization coverage among girls as compared to boys. A study of more than 4000 rural Indian children in 1993-1994 indicated that fewer than 55% of children were fully vaccinated and that girls had a 5% lower coverage compared to boys . In 1992, Bonu et al evaluated vaccination coverage among children aged 12-35 months before and after a three-year government vaccination-awareness program in rural areas of four north Indian states. Prior to the program, girls were found to be at a disadvantage compared to boys and the differences in coverage by gender persisted following the program's completion . Other studies reviewed indicated lower immunization coverage for girls compared to boys, although differences were non-significant [22,23].
We compiled data from these four studies comprising nine sub-samples (based on a combination of different age groups and antigens) to obtain an overall ratio of coverage (girls vs. boys). We observed an overall coverage ratio estimate of 0.93 (95% CI: 0.90, 0.9, Figure 1) - indicating that among these studies girls were 7% less likely to be immunized when compared to boys (p<0.001).
Figure 1. Girl-to-boy ratios of immunization coverage and combined estimates derived from previously published studies. The girl-to-boy immunization coverage ratios are based on the results of studies where data was available for calculation of pooled estimates. A CR of less than 1.0 indicates higher coverage in favour of boys.
This study uses data from three consecutive rounds of the Indian National Family Health Survey (NFHS) [24-26]. The International Institute for Population Sciences coordinated each round of the survey with support from several international organizations. The three cross-sectional surveys were conducted during 1992-93, 1998-99 and 2005-06. A summary of the coverage and target population for each round is presented in Table 1. The sampling, questionnaire structure, and content of the NFHS surveys follow what has been adopted by the Demographic Health Surveys (DHS) in other developing countries. The NFHS uses nationally representative area-based sampling frames in each survey . The NFHS produced high response rates in all states. Details of the survey methodology and response rates have been published for each round of the survey [24-26].
Table 1. Overview of India's National Family Health Survey (NFHS).
Sample for analysis
Our sample for analysis includes all children below five years of age with complete immunization histories (N = 121,100). The 1998-1999 survey only included children up to 35 months of age at the time of the survey. About 3% of children were excluded due to missing data on immunization coverage. Total sample sizes of children under five along with analysis samples for each round of the NFHS are detailed in Table 1.
Indicators and measures
We defined immunization coverage as up to date, age-appropriate immunization coverage. Standard indicators of immunization coverage are based on the percentage of children who have accumulated the required number of vaccines by a certain age, regardless of timeliness. Age-appropriate vaccination has been shown to be an important component of infection control [28,29] by reducing transmissibility in susceptible populations [30,31] and by increasing the probability of survival . We determined age-appropriate immunization coverage for each antigen using a combination of data from the child's immunization card and maternal recall when cards were unavailable. Previous studies have demonstrated that maternal recall can be a robust estimation of immunization coverage in settings where complete records are not available .
Immunization information was available for the following antigens: bacille Calmette-Guérin (BCG), oral polio vaccine (OPV), diphtheria, pertussis (whooping cough) and tetanus (DPT) vaccine, and measles vaccine. We considered children age-appropriately immunized if they had received all immunizations for their age according to the WHO's Expanded Program on Immunization (EPI) immunization schedule. Modelled on the WHO guidelines, the government of India's Universal Immunization Program (UIP) was introduced in 1985 and includes one dose of BCG (at birth), three doses of OPV and DPT (at 6, 10, and 14 weeks), and one dose of measles (at nine months) . India's EPI/UIP schedule used for our age-appropriate classification is detailed in Figure 2.
Figure 2. Recommended expanded program of immunization (EPI) schedule for India. *OPV-0 is an additional dose of polio given at birth, but is not part of India's national immunization program. ✝Dashed lines indicate ages (1,2,3,5, and 9 months) used in determining appropriate immunization coverage within the child's first year. Children were considered to have age-appropriate EPI coverage if they had received all antigens recommended for their age.
Using the child's age in months and the EPI schedule, a composite binary variable indicating EPI complete (yes or no) was created to represent the overall age-appropriate immunization status of each child as follows:
0-1 month: child was considered age-appropriately immunized (EPI=1) if they had received BCG;
2-3 months: child was considered age-appropriately immunized (EPI=1) if they had received BCG and two doses of OPV and DPT (one dose of OPV and DPT if aged two months);
4-8 months: child was considered age-appropriately immunized (EPI=1) if they had received BCG and three doses of OPV and DPT;
9 months and older: child was considered age-appropriately immunized (EPI=1) if they had received BCG, three doses of OPV and DPT, and one dose of measles.
To study the influence of birth order and gender of the older siblings, we calculated the birth order and gender of each child in relation to the birth order and gender of their siblings. In a subset of children for whom the complete date of birth (day, month, and year) was known and complete date of immunization was recorded on the immunization card, we calculated age of vaccine receipt for all EPI antigens.
The analyses in this paper are primarily descriptive and present gender differences in immunization coverage by antigen, birth order, year of birth, and state across the three rounds of the NFHS survey. Using the composite EPI age-appropriate variable, we examined gender differences in coverage by birth order and sibling composition. We also examined the change in age-appropriate coverage by birth cohort (based on year of birth) for each EPI antigen. Births that occurred near to the time of the survey are excluded from the cohort analyses in order to prevent underestimates of coverage due to reduced opportunity to receive complete immunizations among these children. We instead report proportion of children not immunized for these birth cohorts. Gender differences in immunization coverage are presented at the state and national level. Sampling weights were used for all analyses. We tested differences between proportions using t statistics. Data were managed and analyzed using Stata (version 10) statistical software .