Explaining socioeconomic inequalities in immunisation coverage in India: new insights from the fourth National Family Health Survey (2015–16)

Over the past several decades, there has been a significant reduction in child mortality rates across the world. Globally, the under-five mortality rate has declined from 90.6 deaths per 1000 live births in 1990 to 42.5 deaths per 1000 live births in 2015 [1]. Proportionally and in absolute numbers, more childhood deaths occurred in low- and middle-income countries (LMICs) than elsewhere in the world [2, 3]. An important factor for preventing diseases and death in childhood is immunisation, which has played a critical role in the drop in child mortality rates globally. Arising from the efficacy of immunisations in improving health and reducing mortality, the United Nations set childhood immunisation coverage as a key indicator to monitor the fourth Millennium Development Goal (MDG-4), which aimed to reduce the under-five mortality rate by two-thirds between 1990 and 2015. While there was substantial progress on this goal, ultimately it was not achieved. The post-2015 Sustainable Development Goals (SDGs) thus continue to target mortality reductions through 2030. SDG 3 aims to ensure health and well-being for all, including achievement of universal immunisation coverage. The new Sustainable Development Agenda also places a strong emphasis on reducing inequalities. Monitoring not only of immunisation coverage, but also of inequalities, is therefore essential for meeting the new SDGs.

India was among the list of countries that did not meet MDG-4, and the latest evidence suggests that only 62% of children aged 12–23 months have been fully immunised—that is, that they’ve received BCG, measles, and 3 doses of both the polio and diphtheria, pertussis and tetanus (DPT) vaccines. This is far from the universal coverage targeted by SDG 3. However, improving immunisation coverage has long been a public health goal in India. The Government of India launched the Universal Immunisation Programme (UIP) in 1985 to prevent infant and child mortality from six preventable diseases: Tuberculosis, Diphtheria, Pertussis, Tetanus, Poliomyelitis and Measles [4]. The UIP specifies that by 12 months of age, children should be fully immunised. More recently, Hepatitis B was also included under the UIP in India. Details for the recommended timing for these vaccinations are presented in Table 1.

Meanwhile, pioneering strategies such as the Pulse Polio campaign were introduced to reduce the incidence of polio in India. As a result, India faced a drastic decline in polio incidence by the end of 2012, especially among marginalized populations [5]. It was certified as polio-free by the WHO in 2014, and has since retained that status [6]. Less progress has been made on other diseases of childhood. A substantial number of child deaths in India occur due to vaccine-preventable diseases—particularly measles, Hepatitis B and Haemophilus influenza type b (Hib) [7]. In 2011, the Hib vaccine was introduced for the first time in two southern states, in combination with DPT and Hepatitis B. Following on from this, in 2015 the Hib-conjugate vaccine was introduced under the UIP for the entire national population.

Corresponding to these government efforts, progress has been made, but full immunisation coverage is still low. The National Family Health Survey (NFHS), a repeated cross-sectional national survey and a key source of information on immunisation coverage in India, shows that full immunisation coverage has increased from 35% in the NFHS-1 (1992–93) data to 62% in the NFHS-4 (2015–16). Substantial variation was reported in coverage of specific doses of vaccines. Estimates from the NFHS-4 (2015–16) show that, for children aged 12–23 months, coverage of Hepatitis B vaccine was lowest (63%), while the highest coverage was reported for BCG (92%) vaccination. The NFHS-4 also indicates that full immunisation coverage varies considerably according to geographic region, place of residence, and socioeconomic status. Full coverage was lowest in Nagaland (35%), a state in the Northeast of India, and was highest in Puducherry (95%) in the South. Using a sub-sample (n = 9582) of data from the NFHS-3 (2005–06), Lauridsen and Pradhan reported socioeconomic inequalities associated with child immunisation in India [8]. Another study using the District Level Household and Facility Survey (2007–08), also documented socioeconomic disparities in coverage of full immunisation in India in a selected sub-sample (N = 11,212) [9]. A growing number of studies have examined socioeconomic inequalities in child immunisation in LMICs, including India. However, the pathways through which inequalities occur remain unclear. Very few studies from India have systematically examined socioeconomic inequalities in child immunisation, and previous work on this topic in India has tended to analyse selective sub-samples. Therefore, using large-scale survey data from the most recent round of the NFHS (2015–16), in this study we examine inequalities in immunisation coverage for children aged 12–59 months in India, focusing on three immunisation categories: full, partial and no immunisation coverage. We also assess socioeconomic inequalities in the intensity of immunisation coverage in India, and document some of the other key socio-demographic correlates of disparities in coverage of child immunisation.

Using nationally representative data from the latest round of the NFHS (2015–16), we examined the extent of inequalities in childhood immunisation (12–59 months) in six regions and five socioeconomic groups in India, with focus on factors associated with full, partial, and no immunisation in India. Overall, we found strong evidence of a socioeconomic and geographic gradient in immunisation, with fully immunised children disproportionately concentrated in households in the highest wealth quintiles, and residing in urban areas and the southern and western regions of the country. Meanwhile, we found that partially and never immunised children are in lower wealth quintiles, rural areas, and northern regions. These findings corroborate those of previous studies from other countries, and earlier studies from India [8, 22, 23]. We also examined socioeconomic inequality in immunisation intensity in our analysis. Inclusion of immunisation intensity is important as it uncovers the factors associated with the additive receipt of more vaccines among partially immunised children. Findings indicate a concentration of higher immunisation intensity among the highest wealth quintile. This complements a similar finding reported in a previous study from Nigeria [24].

Our findings suggest that mother’s education is an important factor that contributes to the disparities in immunisation coverage across different socioeconomic groups, different regions, and by place of residence. This finding is consistent with the earlier studies from India [25‐28] that argue that higher maternal education leads to an increase in the utilisation of health care services, which in turn facilitates vaccine uptake. Our complementary findings suggest that the inequalities in immunisation found here are attributable to changes in level of maternal education, place of residence, geographical region, and wealth quintile. Nor are these factors independent of one another: the proportion of illiterate mothers is higher in rural (36%) than urban (16%) areas, and poorer households have a higher proportion of illiterate mothers (63%), while richer households have a lower proportion of illiterate mothers (4%). Geographic regions with poor immunisation coverage (western, north-eastern and some parts of the west and central regions) also have a higher proportion of illiterate mothers.

Our study shows that full vaccination coverage is more prevalent among well-off households, while partial and non-immunisation are more prevalent among economically deprived households. This finding is consistent with previous studies which also show that higher socioeconomic status is associated with higher immunisation rates [29].

We also identified place of residence as an important factor that contributes to the disparities in childhood immunisation in India. Research using previous rounds of the NFHS has also found low coverage of immunisation among children in rural compared to urban locations [10, 30‐32]. It has been suggested that, in rural areas, rates of full immunisation can be improved by increasing health services through immunisation camps and providing incentives to mothers [33]. These findings highlight expanded health facilities and broader improvements to the health system as an important supply-side function. Previous research also suggests there may be some demand-side functions (acceptability factors, such as culture and expectations that parents have of the health system) which could also affect the uptake of maternal and child healthcare in general [34, 35] and immunisation in particular [36, 37].

Our findings also highlight considerable regional disparities in non-immunisation across the country. In general, the states with the lowest proportion of fully immunised children are clustered in the central, eastern, north-eastern (except Sikkim) regions, and a few states of the western region. On the other end of the spectrum, all of the southern states are performing very well on immunisation coverage, with high rates across the region. An encouraging finding from our study is the improvement in functionality of healthcare system with respect to immunisation, reflected by the relatively small percent of non-immunised children compared to previous periods.

One further factor strongly associated with the wide disparity in immunisation coverage in our study is the use of institutional delivery facilities for childbirth. There are several possible explanations of this association, which are not mutually exclusive: First, Janani Suraksha Yojana (JSY), India’s conditional cash transfer program which aims to reduce the maternal mortality ratio through promotion (using cash incentives) of institutional deliveries, has improved reproductive and child health-related indicators in India [38]. Although childhood vaccines are scheduled up to the age of 12 months, several vaccines, such as polio, hepatitis B, and BCG, take place at the time of birth [39]; interaction with community health workers through JSY and institutional delivery may facilitate vaccination at birth. Second, women’s interaction with health care providers and the health system may increase the awareness of other health issues which can occur in the post-partum period, and thereby encourage continued care throughout the child’s first years of life.

There are many unexplained factors associated with partial vaccination and non-vaccination among Indian children which we were not able to explore in this study. For instance, one study in northern India found that a substantial proportion of mothers (12%) failed to give a specific reason for why their children had not received vaccinations [40]. Dropout rates of some or all vaccines raise several questions about supply and demand-side factors. One study examined the reason behind partial and non-immunisation of children in Lucknow district in India. Lack of knowledge and lack of faith were found to be the main reasons for non-immunisation of children [41]. Additional demand-side factors include a knowledge gap about the benefits of immunisation, mothers’ limited awareness of childhood immunisation schedules and sources, and lack of exposure to the media [42, 43].

Regional disparities in non-immunisation and partial immunisation can be attributed not only to demand, but also to supply-side factors. India’s vaccine deficit system may therefore also be a reason for non-vaccination or partial vaccination of children [44]. Supply-side factors include failure of health workers to arrive on time and/or reliably and inadequate supplies of vaccines [45]. Even though immunisation is free in India, travel costs and opportunity costs associated with waiting times can be high, and may be seen as particularly insurmountable for female children and families residing in rural areas [11].

Findings from this study provide evidence of continuing, current socioeconomic inequalities in child immunisation in India, and document factors associated with these inequalities. From a policy and health systems planning perspective, our study is useful to address the challenge of low immunisation and to eliminate vaccine-preventable deaths.