Background

Pakistan faces huge challenges in eradicating polio due to widespread poliovirus transmission and security challenges. Innovative interventions are urgently needed to strengthen community buy-in, to increase the coverage of oral polio vaccine (OPV) and other routine immunisations, and to enhance immunity through the introduction of inactivated polio vaccine (IPV) in combination with OPV. We aimed to evaluate the acceptability and effect on immunisation coverage of an integrated strategy for community engagement and maternal and child health immunisation campaigns in insecure and conflict-affected polio-endemic districts of Pakistan.

Methods

We did a community-based three-arm cluster randomised trial in healthy children aged 1 month to 5 years that resided within the study sites in three districts of Pakistan at high risk of polio. Clusters were randomly assigned by a computer algorithm using restricted randomisation in blocks of 20 by an external statistician (1:1:1) to receive routine polio programme activities (control, arm A), additional interventions with community outreach and mobilisation using an enhanced communication package and provision of short-term preventive maternal and child health services and routine immunisation (health camps), including OPV (arm B), or all interventions of arm B with additional provision of IPV delivered at the maternal and child health camps (arm C). An independent team conducted surveys at baseline, endline, and after each round of supplementary immunisation activity for acceptability and effect. The primary outcome measures for the study were coverage of OPV, IPV, and routine extended programme on immunisation vaccines and changes in the proportion of unvaccinated and fully vaccinated children. This trial is registered with ClinicalTrials.gov , number NCT01908114 .

Findings

Between June 4, 2013, and May 31, 2014, 387 clusters were randomised (131 to arm A, 127 to arm B, and 129 to arm C). At baseline, 28 760 children younger than 5 years were recorded in arm A, 30 098 in arm B, and 29 126 in arm C. 359 clusters remained in the trial until the end (116 in arm A, 120 in arm B, and 123 in arm C; with 23 334 children younger than 5 years in arm A, 26 110 in arm B, and 25 745 in arm C). The estimated OPV coverage was 75% in arm A compared with 82% in arm B (difference vs arm A 6·6%; 95% CI 4·8–8·3) and 84% in arm C (8·5%, 6·8–10·1; overall p<0·0001). The mean proportion of routine vaccine doses received by children younger than 24 months of age was 43% in arm A, 52% in arm B (9%, 7–11) and 54% in arm C (11%, 9–13; overall p<0·0001). No serious adverse events requiring hospitalisation were reported after immunisation.

Interpretation

Despite the challenges associated with the polio end-game in high-risk, conflict-affected areas of Pakistan, a strategy of community mobilisation and targeted community-based health and immunisation camps during polio immunisation campaigns was successful in increasing vaccine coverage, including polio vaccine coverage.

Funding

Bill & Melinda Gates Foundation.

Pakistan, Afghanistan, and Nigeria are the only three remaining countries with endemic polio. ¹ Although the number of polio cases and their geographical spread have reduced, insecurity, poor access to populations, and residual pockets of circulating poliovirus in these three countries remain an important challenge for global polio eradication. Most routine childhood immunisations in Pakistan are delivered at fixed immunisation sites, with some outreach services through vaccinators; however, coverage rates for many routine childhood immunisation vaccines remain low, on average between 65% and 73% for vaccines containing diphtheria, tetanus, and pertussis (DTP). ² Oral polio vaccine (OPV) is delivered differently. Although routine childhood immunisation services should provide four doses of OPV (at birth, 6, 10, and 14 weeks of age), repeated, concerted door-to-door immunisation campaigns, called supplementary immunisation activities, have been used to try to increase OPV coverage. ³ The supplementary immunisation activities are household-level campaigns organised by the Pakistan national polio programme and usually last 5 days (3 days to visit all households, with 2 days for return visits to households with initially absent or missed children with door-to-door OPV administration to children younger than 5 years of age by health workers. These children have their fingers marked using permanent ink for ease of identification in post-vaccination mop-up activities and surveys. Supplementary immunisation activities have been particularly challenging in parts of the country affected by insurgency and insecurity, with groups such as the Taliban limiting access to populations, ⁴ disinformation leading to refusal of OPV, ⁵ and attacks targeting polio workers. ⁶ In particular, in the high-risk areas of northwest Pakistan and several slums of Karachi, polio workers have been subjected to several attacks and assassinations, with bans imposed on polio vaccination activities by the Pakistani Taliban and other extremist groups, as well as general insecurity impeding the access of polio programme teams to such communities. ⁷ These barriers to the polio programme activities are compounded by inefficiencies within the routine childhood immunisation programme, the poor state of environmental sanitation, and high burdens of childhood diarrhoea and malnutrition, which make transmission more probable and potentially impair the response to OPV. ^{8 ; 9 ; 10} An important issue in many areas is insufficient community buy-in for the polio-focused supplementary immunisation activities and general fatigue with the repeated rounds of household OPV administration (estimated to have exceeded 150 rounds to date).