Evolution of Inactivated Poliovirus Vaccine Use for the Endgame and Beyond

Current and next-generation formulation strategies for inactivated polio vaccines to lower costs, increase coverage, and facilitate polio eradication

Implementation of inactivated polio vaccines (IPV) containing Sabin strains (sIPV) will further enable global polio eradication efforts by improving vaccine safety during use and containment during manufacturing. Moreover, sIPV-containing vaccines will lower costs and expand production capacity to facilitate more widespread use in low- and middle-income countries (LMICs). This review focuses on the role of vaccine formulation in these efforts including traditional Salk IPV vaccines and new sIPV-containing dosage forms. The physicochemical properties and stability profiles of poliovirus antigens are described. Formulation approaches to lower costs include developing multidose and combination vaccine formats as well as improving storage stability. Formulation strategies for dose-sparing and enhanced mucosal immunity include employing adjuvants (e.g. aluminum-salt and newer adjuvants) and/or novel delivery systems (e.g. ID administration with microneedle patches). The potential for applying these low-cost formulation development strategies to other vaccines to further improve vaccine access and coverage in LMICs is also discussed.

The mechanisms of action of Plasmodium infection against cancer

Our murine cancer model studies have demonstrated that Plasmodium infection activates the immune system that has been inhibited by cancer cells, counteracts tumor immunosuppressive microenvironment, inhibits tumor angiogenesis, inhibits tumor growth and metastasis, and prolongs the survival time of tumor-bearing mice. Based on these studies, three clinical trials of Plasmodium immunotherapy for advanced cancers have been approved and are ongoing in China. After comparing the mechanisms of action of Plasmodium immunotherapy with those of immune checkpoint blockade therapy, we propose the notion that cancer is an ecological disease and that Plasmodium immunotherapy is a systemic ecological counterattack therapy for this ecological disease, with limited side effects and without danger to public health based on the use of artesunate and other measures. Recent reports of tolerance to treatment and limitations in majority of patients associated with the use of checkpoint blockers further support this notion. We advocate further studies on the mechanisms of action of Plasmodium infection against cancer and investigations on Plasmodium-based combination therapy in the coming future.

Safety and immunogenicity of inactivated poliovirus vaccine schedules for the post-eradication era: a randomised open-label, multicentre, phase 3, non-inferiority trial

BACKGROUND

Following the global eradication of wild poliovirus, countries using live attenuated oral poliovirus vaccines will transition to exclusive use of inactivated poliovirus vaccine (IPV) or fractional doses of IPV (f-IPV; a f-IPV dose is one-fifth of a normal IPV dose), but IPV supply and cost constraints will necessitate dose-sparing strategies. We compared immunisation schedules of f-IPV and IPV to inform the choice of optimal post-eradication schedule.

METHODS

This randomised open-label, multicentre, phase 3, non-inferiority trial was done at two centres in Panama and one in the Dominican Republic. Eligible participants were healthy 6-week-old infants with no signs of febrile illness or known allergy to vaccine components. Infants were randomly assigned (1:1:1:1, 1:1:1:2, 2:1:1:1), using computer-generated blocks of four or five until the groups were full, to one of four groups and received: two doses of intradermal f-IPV (administered at 14 and 36 weeks; two f-IPV group); or three doses of intradermal f-IPV (administered at 10, 14, and 36 weeks; three f-IPV group); or two doses of intramuscular IPV (administered at 14 and 36 weeks; two IPV group); or three doses of intramuscular IPV (administered at 10, 14, and 36 weeks; three IPV group). The primary outcome was seroconversion rates based on neutralising antibodies for poliovirus type 1 and type 2 at baseline and at 40 weeks (4 weeks after the second or third vaccinations) in the per-protocol population to allow non-inferiority and eventually superiority comparisons between vaccines and regimens. Three co-primary outcomes concerning poliovirus types 1 and 2 were to determine if seroconversion rates at 40 weeks of age after a two-dose regimen (administered at weeks 14 and 36) of intradermally administered f-IPV were non-inferior to a corresponding two-dose regimen of intramuscular IPV; if seroconversion rates at 40 weeks of age after a two-dose IPV regimen (weeks 14 and 36) were non-inferior to those after a three-dose IPV regimen (weeks 10, 14, and 36); and if seroconversion rates after a two-dose f-IPV regimen (weeks 14 and 36) were non-inferior to those after a three-dose f-IPV regimen (weeks 10, 14, and 36). The non-inferiority boundary was set at -10% for the lower bound of the two-sided 95% CI for the seroconversion rate difference.. Safety was assessed as serious adverse events and important medical events. This study is registered on ClinicalTrials.gov, NCT03239496.

FINDINGS

From Oct 23, 2017, to Nov 13, 2018, we enrolled 773 infants (372 [48%] girls) in Panama and the Dominican Republic (two f-IPV group n=217, three f-IPV group n=178, two IPV group n=178, and three IPV group n=200). 686 infants received all scheduled vaccine doses and were included in the per-protocol analysis. We observed non-inferiority for poliovirus type 1 seroconversion rate at 40 weeks for the two f-IPV dose schedule (95·9% [95% CI 92·0-98·2]) versus the two IPV dose schedule (98·7% [95·4-99·8]), and for the three f-IPV dose schedule (98·8% [95·6-99·8]) versus the three IPV dose schedule (100% [97·9-100]). Similarly, poliovirus type 2 seroconversion rate at 40 weeks for the two f-IPV dose schedule (97·9% [94·8-99·4]) versus the two IPV dose schedule (99·4% [96·4-100]), and for the three f-IPV dose schedule (100% [97·7-100]) versus the three IPV dose schedule (100% [97·9-100]) were non-inferior. Seroconversion rate for the two f-IPV regimen was statistically superior 4 weeks after the last vaccine dose in the 14 and 36 week schedule (95·9% [92·0-98·2]) compared with the 10 and 14 week schedule (83·2% [76·5-88·6]; p=0·0062) for poliovirus type 1. Statistical superiority of the 14 and 36 week schedule was also found for poliovirus type 2 (14 and 36 week schedule 97·9% [94·8-99·4] vs 10 and 14 week schedule 83·9% [77·2-89·2]; p=0·0062), and poliovirus type 3 (14 and 36 week schedule 84·5% [78·7-89·3] vs 10 and 14 week schedule 73·3% [65·8-79·9]; p=0·0062). For IPV, a two dose regimen administered at 14 and 36 weeks (99·4% [96·4-100]) was superior a 10 and 14 week schedule (88·9% [83·4-93·1]; p<0·0001) for poliovirus type 2, but not for type 1 (14 and 36 week schedule 98·7% [95·4-99·8] vs 10 and 14 week schedule 95·6% [91·4-98·1]), or type 3 (14 and 36 week schedule 97·4% [93·5-99·3] vs 10 and 14 week schedule 93·9% [89·3-96·9]). There were no related serious adverse events or important medical events reported in any group showing safety was unaffected by administration route or schedule.

INTERPRETATION

Our observations suggest that adequate immunity against poliovirus type 1 and type 2 is provided by two doses of either IPV or f-IPV at 14 and 36 weeks of age, and broad immunity is provided with three doses of f-IPV, enabling substantial savings in cost and supply. These novel clinical data will inform global polio immunisation policy for the post-eradication era.

FUNDING

Bill & Melinda Gates Foundation.