Factors Associated with Vaccine Refusal (Polio and Routine Immunization) in High-Risk Areas of Pakistan: A Matched Case-Control Study

"Suboptimal vaccine uptake and increased refusal of routine immunization and polio vaccines result from a complex interaction between social, behavioral, and cultural factors and logistic barriers..."

Globally, Pakistan ranks third for being home to the highest number of unvaccinated children (1.2 million), after Nigeria and India, and it is one of two remaining polio-endemic countries (along with Afghanistan). Low immunisation levels are responsible for the high prevalence of vaccine-preventable diseases and the persistence of polio in the high-risk circulation areas of the country. Nested within an implementation research project in Pakistan, this study sought to determine the social-behavioural and cultural reasons and factors for polio non-receipt children (zero doses for the oral polio vaccine - OPV) and routine immunisation (RI) non-receipt children. The study also assessed barriers related to personal and immuniation systems affecting routine and polio immunisation during national immunisation days (NIDs) and supplementary immunisation activities (SIAs).

The Aga Khan University conducted a matched case-control study from April to July 2017 in 8 super-high-risk union councils of 5 towns in Karachi, Pakistan. A total of 3 groups, each with 250 "cases" (Groups A-C), were matched with 1,500 controls (500 in each group) and identified using surveillance records. Group A: refused RI (measles, pentavalent, pneumococcal conjugate vaccine (PCV), and Bacille Calmette-Guérin, or BCG) but accepted OPV; Group B: refused OPV during NIDs and SIAs but accepted RI; and Group C: refused OPV, inactivated polio vaccine (IPV), and RI during the first 5 years of life through Expanded Programme on Immunization (EPI) and polio campaigns. Controls were defined as children between 0-59 months of age who lived in the same catchment area as the cases and completed their immunisation according to their age. Sociodemographic characteristics, household information, and immunisation history were assessed. Data were analysed in STATA using conditional logistic regression.

The study demonstrated that education substantially affects mothers'/families' acceptance of RI for their under-5 children. A greater proportion of RI refusal cases (91.3%) were illiterate compared to the controls (76%). The role of education in impacting health literacy is well established, enabling mothers to make more informed health decisions. Individuals with a higher level of education are more likely to understand the risk of vaccine-preventable diseases, the effectiveness of vaccines, the use of selective information sources, dependence on critical thinking, and the importance of making more proactive decisions. The finding that only 8.7% of cases in the RI refusal group were literate is concerning.

In addition, fear of vaccines' adverse effects was associated with a 6.05-fold increase in the likelihood of RI refusal among cases. Coupled with false assumptions and doubts surrounding vaccines, these fears can lead to refusals among parents.

On the other hand, OPV refusals were linked to the mother's decision authority and the assumption that the OPV caused infertility. Over half of the respondent mothers in each refusal group reported needing permission from another family member (husband, mother-in-law, brother-in-law, or father-in-law) for their child's vaccination, reflecting the existing social and familial structures and lack of empowerment, hindering the RI in targeted regions. The fact that mothers who had decision-making authority in this study reported more refusals for OPV reflects the presence of several widespread myths, misunderstandings, and lack of knowledge that give rise to frequent campaigns that the OPV is used as a birth control strategy, that vaccines contain substances forbidden by Islam, and a suspicion that the OPV is a foreign conspiracy and an artificial alteration of the fate determined by God, especially when the disease has not been experienced by vaccine recipient.

Conversely, higher socioeconomic status (SES) and knowledge of and willingness to vaccinate with IPV were inversely associated with RI, and lower SES, walking to the vaccination point, knowledge of IPV, and an understanding of contracting polio were inversely associated with OPV refusals, with the latter two also inversely associated with complete vaccine refusal. Reflecting on the possible reasons behind one of these sets of findings - the connection with SES - the researchers note that vaccination efforts constitute Pakistan's backbone in its fight against polio, and door-to-door campaigns are a vital part of SIAs. Evidence suggests that people are more likely to vaccinate their children if they believe others in their social group do the same or if their religious beliefs match those of others. Around half of the cases in the OPV refusal group belonged to the poorest to middle SES. These mothers were more likely to accept the OPV if they perceived their neighbours/social groups accepted it during the campaigns, encouraging them to vaccinate their children. This logic may be particularly applicable in Pakistan, where the vaccination experience is socially mediated.

Based on the findings, in order to address vaccine refusals and reduce the "zero dosers", the researchers recommend:

• Parents must be educated to overcome misconceptions, false beliefs, and concerns related to vaccines.
• Parents who immunise their children should be reinforced so as to prevent them from experiencing weariness. (Pakistan conducts multiple campaigns every year, with a greater number of campaigns in regions with the highest risk of transmission.) Immunising children may not be a priority for mothers or caregivers who are overburdened with household or work responsibilities. As a result, disadvantaged children may encounter several logistical challenges when trying to access vaccination services.
• A participatory approach should be considered when designing a tailored intervention, where parents and caregivers can become active agents of the desired change.