Achieving high immunogenicity against poliovirus with fractional doses of inactivated poliovirus vaccine in Ecuador-results from a cross-sectional serological survey.

Background: In January 2018, Ecuador changed its routine immunization schedule by replacing one full dose of inactivated poliovirus vaccine (IPV) administered intramuscularly at 2 months of age with two doses of fractional IPV (1/5th of full dose, fIPV) administered intradermally at 2 and 4 months of age; and bivalent oral poliovirus vaccine (serotypes 1 and 3, bOPV) continues to be used. We compared seroprevalence and titres of polio antibodies achieved by the past and the current immunization schedules. Methods: This was a cross-sectional serological survey in children in Ecuador who received bOPV and either one IPV dose in 2017 or two fIPV doses in 2018. One blood sample was collected between October 2020 and March 2021 and analysed for presence of poliovirus neutralizing antibodies at CDC, Atlanta by microneutralization assay. Findings: We obtained 321 analysable samples from 329 (97·6%) enrolled children (160 received IPV and 161 fIPV). For serotype 2, seroprevalence was 50·0% (CI95%= 44·2-55·8%) for IPV and 83·2% (CI95%=78·5-87·1%) for fIPV recipients (p<0·001). Median antibody titers for serotype 2 were significantly lower for IPV than for fIPV recipients (3·0, CI95%= 3 - 3·5 vs. 4·8, CI95%= 4·5 - 5·2, p<0·001). Seroprevalence for serotypes 1 and 3 was above 90% and was not significantly different between IPV and fIPV recipients. Interpretation: Ecuador achieved significantly better poliovirus serotype 2 immunogenicity with two fIPV doses than with one IPV dose, while preserving vaccine supply and reducing costs. Our data provide further evidence that fIPV is a beneficial and potentially a cost-effective option in polio immunization. Funding: WHO obtained funds for the study from Rotary International.

Immunogenicity of Fractional Dose Inactivated Poliovirus Vaccine in India.

INTRODUCTION: Following the withdrawal of Sabin type 2 from trivalent oral poliovirus vaccine (tOPV) in 2016, the introduction of ≥1 dose of inactivated poliovirus vaccine (IPV) in routine immunization was recommended, either as 1 full dose (0.5mL, intramuscular) or 2 fractional doses of IPV (fIPV-0.1mL, intradermal). India opted for fIPV. We conducted a comparative assessment of IPV and fIPV. METHODS: This was a 4-arm, open-label, multicenter, randomized controlled trial. Infants were enrolled and vaccines administered according to the study design, and the blood was drawn at age 6, 14, and 18 weeks for neutralization testing against all 3 poliovirus types. RESULTS: Study enrolled 799 infants. The seroconversion against type 2 poliovirus with 2 fIPV doses was 85.8% (95% confidence interval [CI]: 80.1%-90.0%) when administered at age 6 and 14 weeks, 77.0% (95% CI: 70.5-82.5) when given at age 10 and 14 weeks, compared to 67.9% (95% CI: 60.4-74.6) following 1 full-dose IPV at age 14 weeks. CONCLUSION: The study demonstrated the superiority of 2 fIPV doses over 1 full-dose IPV in India. Doses of fIPV given at 6 and 14 weeks were more immunogenic than those given at 10 and 14 weeks. Clinical Trial Registry of India (CTRI). Clinical trial registration number was CTRI/2017/02/007793.

Evaluating the cost per child vaccinated with full versus fractional-dose inactivated poliovirus vaccine.

INTRODUCTION: Inactivated poliovirus vaccine (IPV) shortages and evidence of improved immunogenicity of two intradermal (ID) fractional IPV (fIPV) doses compared with one full intramuscular dose led to recommendations for fIPV delivery. To provide evidence on the economics of fIPV, we estimated the cost per child vaccinated using full-dose IPV compared with fIPV in routine and campaign settings. We evaluated the impact on costs of alternative devices facilitating ID administration, vaccine vial sizes, and prices. METHODS: We used an Excel-based model to estimate the commodity and delivery costs for providing IPV. Commodity costs included vaccine price per dose adjusted for wastage, prices for vaccine administration devices, and safety boxes. Delivery costs included storage costs at each level of the supply chain, transport costs for commodities between levels, and human resource costs for vaccine administration. Model inputs were obtained from various databases and published literature. All costs are reported in 2018 US dollars. RESULTS: In both campaign and routine settings, fIPV had a lower cost per child vaccinated than full dosing, despite the assumed higher vaccine wastage with fIPV in routine settings, and even when novel ID administration devices were used. In routine settings, costs per child fully vaccinated with fractional doses were 15% to 48% lower than those with full-dose delivery across different vial sizes. The cost per child vaccinated ranged from $1.84 to $2.65 for fractional doses, depending on the administration device, compared with $3.57 for full dose, when using 5-dose vials. The magnitude of cost reductions with fIPV relative to full-dose IPV was largest with smaller vial sizes and higher vaccine price. CONCLUSION: Adopting fIPV can reduce costs per child vaccinated compared with using full doses, especially as IPV prices increase in the short term and more so when two full doses could be recommended in the future.

National introduction of fractional-dose inactivated polio vaccine in Sri Lanka following the global “switch”

As part of the Polio eradication and endgame strategic plan 2013–2018 to achieve and sustain apolio-free world, the use of oral polio vaccine (OPV) must eventually be stopped. This process startedin April 2016, with the worldwide, planned synchronized “switch”, whereby use of OPV containingpoliovirus type 2 ceased. Prior to the switch, in line with international guidance on risk mitigation, SriLanka had introduced a single full dose (0.5 mL intramuscularly) of inactivated polio vaccine (IPV)into routine immunization. However, the two global suppliers of World Health Organization (WHO)-prequalified IPV had significant challenges in scaling up production to meet the new demand, resultingin a global shortage in April 2016. The WHO Strategic Advisory Group of Experts on Immunizationrecommended that countries should consider a two-dose schedule of intradermal fractional IPV (fIPV).After rapid consideration of the programmatic cost and logistic implications, Sri Lanka was the firstcountry to roll out this dose-sparing schedule nationwide. The country ensured smooth implementationof fIPV use, reaching out to all eligible infants, maintaining equity and sustaining the IPV vaccination.With expedited refresher training in intradermal vaccination, confident, well-trained and dedicatedhealth-care staff, from the field up to provincial levels, worked together as a dedicated team. Healthauthorities at all levels reported that public acceptance of the additional injections of the new schedulewas high. A post-introduction evaluation and an assessment of population-level immunity are under way

National introduction of fractional-dose inactivated polio vaccine in Sri Lanka following the global "switch".

As part of the Polio eradication and endgame strategic plan 2013-2018 to achieve and sustain a polio-free world, the use of oral polio vaccine (OPV) must eventually be stopped. This process started in April 2016, with the worldwide, planned synchronized "switch", whereby use of OPV containing poliovirus type 2 ceased. Prior to the switch, in line with international guidance on risk mitigation, Sri Lanka had introduced a single full dose (0.5 mL intramuscularly) of inactivated polio vaccine (IPV) into routine immunization. However, the two global suppliers of World Health Organization (WHO)-prequalified IPV had significant challenges in scaling up production to meet the new demand, resulting in a global shortage in April 2016. The WHO Strategic Advisory Group of Experts on Immunization recommended that countries should consider a two-dose schedule of intradermal fractional IPV (fIPV). After rapid consideration of the programmatic cost and logistic implications, Sri Lanka was the first country to roll out this dose-sparing schedule nationwide. The country ensured smooth implementation of fIPV use, reaching out to all eligible infants, maintaining equity and sustaining the IPV vaccination. With expedited refresher training in intradermal vaccination, confident, well-trained and dedicated health-care staff, from the field up to provincial levels, worked together as a dedicated team. Health authorities at all levels reported that public acceptance of the additional injections of the new schedule was high. A post-introduction evaluation and an assessment of population-level immunity are under way.