Epidemiology of the Unimmunized Child: Findings from the Peer-Reviewed Published Literature

In an attempt to understand reasons behind the failure to immunise children in developing countries, the Global Immunization Division (GID) of the United States Centers for Disease Control and Prevention (CDC) conducted a parallel review of grey literature that had been carried out at the request of the World Health Organization (WHO) by IMMUNIZATIONbasics - the global United States Agency for International Development (USAID)-funded project (2004 to 2009). (See Related Summaries, below.)

As part of CDC's review of the peer-reviewed literature, GID searched 8 medical and behavioural and social science literature databases for relevant articles published between 1999 and 2009. Abstracted reasons for unimmunisation and factors were categorised into 4 major themes: Immunisation Systems, Communication and Information, Family Characteristics, and Parental Attitudes and Knowledge. Sub-categories were created within each of these themes. The initial database search identified 16,097 possibly relevant articles; a total of 901 reasons and factors associated with the under-vaccinated child were identified from the 209 articles that eventually made it to the review stage.

Of these reasons and factors, 393 (44%) were related to immunisation systems, 255 (28%) to parental attitudes and knowledge, 199 (22%) to family characteristics, and 58 (6%) to communication and information. Thirty-three reasons and factors were abstracted from 12 articles describing the completely unvaccinated child. Of these, 4 (12%) were related to immunisation systems, 18 (55%) to parental beliefs and knowledge, 9 (27%) to family characteristics, and 2 (6%) to communication and information. The 58 reasons or factors linked to the latter category were grouped into 9 subcategories (see Table 4). The 4 major sub-categories included: 1) lack of media/radio exposure, 2) poor communication due to perceived provider rudeness or a lack of trust in him/her, 3) the dissemination of inadequate or incorrect information by health care worker, and 4) a lack of community involvement in the Expanded Programme on Immunisation (EPI). "Although communication and information-related reasons/factors were the least frequently linked to low vaccine uptake in the identified literature, these reasons/factors were reported by countries in all WHO regions."

An excerpt from the document follows:

"Several common themes were identified in this review to describe the epidemiology of the under-vaccinated child in low and middle income countries. Access due to geographic barriers (e.g., living in remote/rural areas, clinic too far away) and missed opportunities to vaccinate (e.g., not having a vaccination card at time of visit), for example, were linked to low vaccine uptake in most countries from which articles were identified. Other reasons and factors, especially those linked to parental attitudes and knowledge, such as role of gender, regionally focused and more difficult to interpret. Many of the identified parental attitudes and regarding vaccinations may be 'proxies' for more complex health seeking behaviors and perceived barriers.

In the reviewed literature, the reasons and factors linked to under-vaccination (missing one or more routine vaccinations) were most likely related immunization systems. On the other hand, the reasons/factors associated with being unvaccinated (missing all routine vaccinations) were most likely related to parental attitude or knowledge. The Unvaccinated child may reflect cultural beliefs held by caregivers, regardless of opportunity and access. As stated above, this finding may involve in effect more complex health related behaviors not easily investigated or documented in the published literature.

The findings generated from this systematic literature review only reflect studies and projects from countries that have been published. For example, the reviewed identified the lack of peer-reviewed literature describing reasons and factors associated with low vaccine uptake among children living in Central Africa, certain countries in South East Asia as well as other locations in Eastern Europe...

Recommendations:

• Ongoing collection and review of newly published literature (along with grey literature) regarding the reasons and factors associated with low vaccine uptake is likely to provide additional insight into the findings identified from this systematic review.
• A more detailed investigation of the specific pathways through which certain family characteristics and parental attitudes are linked to the under-vaccinated child would be informative and helpful in improving coverage.
• Additional research on the reasons and factors linked to low vaccine uptake in countries from which no articles were identified, such as the Democratic Republic of Congo, may prove beneficial.
• Further investigation of gender, both of the child and caregiver as well as the health care worker, could provide insight into reasons for low vaccine uptake within certain high-risk areas.
• Findings from this review along with results from the analysis of the grey literature and DHS [Demographic and Health Survey] data could be used to develop pilot intervention projects designed to improve vaccine uptake in countries with known low routine vaccination coverage."