Immunogenicity of Intramuscular Fractional Dose of Inactivated Poliovirus Vaccine.

BACKGROUNDS: Intradermal (id) fractional inactivated poliovirus vaccine ([fIPV] one fifth of normal IPV dose) is safe and immunogenic; however, id administration is perceived as difficult. We compared fIPV immunogenicity administered id or intramuscularly (im). METHODS: This noninferiority trial was conducted among polio vaccine-naive Cuban infants who received 2 IPV doses at 4 and 8 months of age. Infants were randomized into 4 arms: (A) fIPV, 0.1 mL im; (B) fIPV, 0.2 mL im; (C) fIPV, 0.1mL id; and (D) IPV, 0.5 mL im. Blood collected before and after vaccinations was tested for poliovirus-neutralizing antibodies. RESULTS: A total of 196 of 214 (91.6%) enrolled children completed study. Seroconversion after 2 IPV doses in each arm were as follows: (A) 97.3% (90.6-99.7), 98.7% (92.7-99.9), and 90.5% (81.5-96.1) for serotypes 1, 2, and 3, respectively; (B) 97.2% (90.3-99.7), 100%, 95.8% (88.3-99.1) for serotypes 1, 2, and 3, respectively; (C) 89.3% (71.8-97.7), 92.9% (76.5-99.1), 82.1% (63.1-93.9) for serotypes 1, 2, and 3, respectively; and (D) 100%, 100%, 100% for serotypes 1, 2, and 3, respectively. Seroconversion with fIPV im was noninferior to fIPV id for all serotypes. CONCLUSIONS: We demonstrated noninferiority of fIPV im compared with id when administered at 4 and 8 months of age. Further investigations in an earlier infant schedule should be pursued to explore fIPV im as option for dose-sparing strategy in countries reluctant to use fIPV id due to programmatic difficulties of id administration.

Does Simultaneous Administration of Bivalent (Types 1 and 3) Oral Poliovirus Vaccine and Inactivated Poliovirus Vaccine Induce Mucosal Cross-immunity to Poliovirus Type 2?

Background: Inactivated poliovirus vaccine (IPV) alone does not induce mucosal immunity. However, it was hypothesized that administration of IPV together with bivalent (types 1+3) oral poliovirus vaccine (bOPV) may stimulate mucosal cross-immunity to poliovirus type 2 (PV2). Methods: Cuban infants were randomized to receive either one dose of IPV (Arm A); one dose of IPV with bOPV (Arm B) at about 6 months of age or no vaccine (Arm C). Subjects were challenged with one dose of trivalent OPV (tOPV); they were about 7 months old in arms A and B, and about 3 months old in arm C at a time of the tOPV challenge. Sera were collected before vaccination and 30 days after tOPV challenge and tested for presence of poliovirus neutralizing antibodies; stool samples were collected at days 0, 7, 14, 21 and 49 post-challenge and tested for presence of poliovirus. Results: We enrolled 333 children. Excretion of PV2 following tOPV challenge was highest on day 7 (75 [CI 95% = 65-82%], 68 [CI 95% = 58-75%] and 73 [CI 95% = 63-80%] for study arms A, B, and C respectively); excretion decreased with every subsequent stool sampling; no significant differences either in proportion of PV2 excretion or in its duration were observed between study arms. Conclusions: There was no reduction in excretion of PV2 after tOPV challenge in children who had received IPV with bOPV when compared to those who had received IPV alone or no vaccine. Polio eradication program cannot assume any PV2 mucosal response with the current polio immunization schedule. Clinical Trials Registration: The trial was registered with the Australian New Zealand Clinical Trials Registry and allocated trial number ACTRN12616000169448.

Cuba's Scientific Contributions to Global Polio Eradication.

Cuba eliminated polio in 1962 and was among the first countries to do so. Since then, only 20 cases of vaccine-derived paralytic poliomyelitis have been reported. Because Cuba used oral poliovirus vaccine exclusively in two mass campaigns usually in February and April each year, Sabin viruses were detected only within approximately 6-8 weeks after each annual campaign. This made Cuba a very attractive site to study the epidemiology of poliomyelitis in a tropical country without risk of secondary transmission of Sabin viruses for a large part of each year, an advantage over countries that used oral poliovirus vaccine continuously throughout the year in routine immunization programs. This report summarizes the unique scientific collaboration between Cuba's Ministry of Public Health and WHO, with participation by US scientists, in the global effort to eradicate polio. KEYWORDS Poliomyelitis, disease eradication, disease elimination, oral poliovirus vaccine, Sabin vaccine, inactivated poliovirus vaccine, Salk vaccine, Cuba, WHO.

Boosting Immune Responses Following Fractional-Dose Inactivated Poliovirus Vaccine: A Randomized, Controlled Trial.

BACKGROUND: Fractional-dose administration of inactivated poliovirus vaccine (fIPV) could increase IPV affordability and stretch limited supplies. We assessed immune responses following fIPV administered intradermally, compared with full-dose IPV administered intramuscularly, among adults with a history of oral poliovirus vaccine (OPV) receipt. METHODS: We conducted a randomized, controlled noninferiority trial in Cuba. fIPV or IPV were administered on days 0 and 28; serum was collected on days 0, 7, 28, and 56 for analysis by a neutralization assay. The primary end point was seroconversion or a ≥4-fold rise in antibody titer. The noninferiority limit was 10%. The secondary end point was safety, assessed by the number and intensity of adverse reactions. RESULTS: A total of 503 of 534 enrolled participants (94.2%) completed all study requirements. Twenty-eight days after the first dose, 94.8%, 98.0%, and 98.0% of fIPV recipients had an immune response to poliovirus types 1, 2, and 3, respectively, compared with 98.1% (P = .06), 98.0% (P = 1.00), and 99.2% (P = .45) in the IPV arm. Noninferiority was achieved on days 7, 28, and 56 for all serotypes. No serious adverse events were reported. CONCLUSION: fIPV induced similar boosting immune responses, compared with full-dose IPV. This suggests that fIPV would be an effective strategy to boost population immunity in an outbreak situation. CLINICAL TRIALS REGISTRATION: ACTRN12615000305527.

Needle-free jet injector intradermal delivery of fractional dose inactivated poliovirus vaccine: Association between injection quality and immunogenicity.

INTRODUCTION: The World Health Organization recommends that as part of the polio end-game strategy a dose of inactivated poliovirus vaccine (IPV) be introduced by the end of 2015 in all countries currently using only oral poliovirus vaccine (OPV). Administration of fractional dose (1/5 of full dose) IPV (fIPV) by intradermal (ID) injection may reduce costs, but its conventional administration is with Bacillus Calmette-Guerin (BCG) needle and syringe (NS), which is time consuming and technically challenging. We compared injection quality achieved with BCG NS and three needle-free jet injectors and assessed ergonomic features of the injectors. METHODS: Children between 12 and 20 months of age who had previously received OPV were enrolled in the Camaguey, Cuba study. Subjects received a single fIPV dose administered intradermally with BCG NS or one of three needle-free injector devices: Bioject Biojector 2000® (B2000), Bioject ID Pen® (ID Pen), or PharmaJet Tropis® (Tropis). We measured bleb diameter and vaccine loss as indicators of ID injection quality, with desirable injection quality defined as bleb diameter ≥5mm and vaccine loss <10%. We surveyed vaccinators to evaluate ergonomic features of the injectors. We further assessed the injection quality indicators as predictors of immune response, measured by increase in poliovirus neutralizing antibodies in blood between day 0 (pre-IPV) and 21 (post-vaccination). RESULTS: Delivery by BCG NS and Tropis resulted in the highest proportion of subjects with desirable injection quality; health workers ranked Biojector2000 and Tropis highest for ergonomic features. We observed that vaccine loss and desirable injection quality were associated with an immune response for poliovirus type 2 (P=0.02, P=0.01, respectively). CONCLUSIONS: Our study demonstrated the feasibility of fIPV delivery using needle-free injector devices with high acceptability among health workers. We did not observe the indicators of injection quality to be uniformly associated with immune response.

Decay of Sabin inactivated poliovirus vaccine (IPV)-boosted poliovirus antibodies.

INTRODUCTION: We conducted a follow-on study to a phase I randomized, controlled trial conducted in Cuba, 2012, to assess the persistence of poliovirus antibodies at 21-22 months following booster dose of Sabin-IPV compared to Salk-IPV in adults who had received multiple doses of oral poliovirus vaccine (OPV) during childhood. METHODS: In 2012, 60 healthy adult males aged 19-23 were randomized to receive one booster dose, of either Sabin-inactivated poliovirus vaccine (Sabin-IPV), adjuvanted Sabin-IPV (aSabin-IPV), or conventional Salk-IPV. In the original study, blood was collected at days 0 (before) and 28 (after vaccination), respectively. In this study, an additional blood sample was collected 21-22 months after vaccination, and tested for neutralizing antibodies to Sabin poliovirus types 1, 2 and 3. RESULTS: We collected sera from 59/60 (98.3%) subjects; 59/59 (100%) remained seropositive to all poliovirus types, 21-22 months after vaccination. The decay curves were very similar among the study groups. Between day 28 and 21-22 months, there was a reduction of ⩾87.4% in median antibody levels for all poliovirus types in all study groups, with no significant differences between the study groups. CONCLUSION: The decay of poliovirus antibodies over a 21-22-month period was similar regardless of the type of booster vaccine used, suggesting the scientific data of Salk IPV long-term persistence and decay may be broadly applicable to Sabin IPV.

Reactogenicity and immunogenicity of inactivated poliovirus vaccine produced from Sabin strains: a phase I Trial in healthy adults in Cuba.

BACKGROUND: To ensure that developing countries have the option to produce inactivated poliovirus vaccine (IPV), the Global Polio Eradication Initiative has promoted the development of an IPV using Sabin poliovirus strains (Sabin IPV). This trial assessed the reactogenicity and immunogenicity of Sabin IPV and adjuvanted Sabin IPV in healthy adults in Cuba. METHODS: This is a randomized, controlled phase I trial, enrolling 60 healthy (previously vaccinated) male human volunteers, aged 19-23 years to receive one dose of either Sabin IPV (20:32:64 DU/dose), adjuvanted Sabin IPV (10:16:32 DU/dose), or conventional Salk IPV (40:8:32 DU/dose). The primary endpoint for reactogenicity relied on monitoring of adverse events. The secondary endpoint measured boosting immune responses (i.e. seroconversion or 4-fold rise) of poliovirus antibody, assessed by neutralization assays. RESULTS: Sixty subjects fulfilled the study requirements. No serious adverse events reported were attributed to trial interventions during the 6-month follow-up period. Twenty-eight days after vaccination, boosting immune responses against poliovirus types 1-3 were between 90% and 100% in all vaccination groups. There was a more than 6-fold increase in median antibody titers between pre- and post-vaccination titers in all vaccination groups. DISCUSSION: Both Sabin IPV and adjuvanted Sabin IPV were well tolerated and immunogenic against all poliovirus serotypes. This result suggests that the aluminum adjuvant may allow a 50% (or higher) dose reduction.

Priming after a fractional dose of inactivated poliovirus vaccine.

BACKGROUND: To reduce the costs of maintaining a poliovirus immunization base in low-income areas, we assessed the extent of priming immune responses after the administration of inactivated poliovirus vaccine (IPV). METHODS: We compared the immunogenicity and reactogenicity of a fractional dose of IPV (one fifth of a full dose) administered intradermally with a full dose administered intramuscularly in Cuban infants at the ages of 4 and 8 months. Blood was collected from infants at the ages of 4 months, 8 months, 8 months 7 days, and 8 months 30 days to assess single-dose seroconversion, single-dose priming of immune responses, and two-dose seroconversion. Specimens were tested with a neutralization assay. RESULTS: A total of 320 infants underwent randomization, and 310 infants (96.9%) fulfilled the study requirements. In the group receiving the first fractional dose of IPV, seroconversion to poliovirus types 1, 2, and 3 occurred in 16.6%, 47.1%, and 14.7% of participants, respectively, as compared with 46.6%, 62.8%, and 32.0% in the group receiving the first full dose of IPV (P<0.008 for all comparisons). A priming immune response to poliovirus types 1, 2, and 3 occurred in 90.8%, 94.0%, and 89.6% of participants, respectively, in the group receiving the fractional dose as compared with 97.6%, 98.3%, and 98.1% in the group receiving the full dose (P=0.01 for the comparison with type 3). After the administration of the second dose of IPV in the group receiving fractional doses, cumulative two-dose seroconversion to poliovirus types 1, 2, and 3 occurred in 93.6%, 98.1%, and 93.0% of participants, respectively, as compared with 100.0%, 100.0%, and 99.4% in the group receiving the full dose (P<0.006 for the comparisons of types 1 and 3). The group receiving intradermal injections had the greatest number of adverse events, most of which were minor in intensity and none of which had serious consequences. CONCLUSIONS: This evaluation shows that vaccinating infants with a single fractional dose of IPV can induce priming and seroconversion in more than 90% of immunized infants. (Funded by the World Health Organization and the Pan American Health Organization; Australian New Zealand Clinical Trials Registry number, ACTRN12610001046099.).

Randomized controlled clinical trial of fractional doses of inactivated poliovirus vaccine administered intradermally by needle-free device in Cuba.

BACKGROUND: As part of an evaluation of strategies to make inactivated poliovirus vaccine (IPV) affordable for developing countries, we conducted a clinical trial of fractional doses of IPV in Cuba. METHODS: We compared the immunogenicity and reactogenicity of fractional-dose IPV (0.1 mL, or 1/5 of a full dose) given intradermally using a needle-free jet injector device compared with full doses given intramuscularly. Subjects were randomized at birth to receive IPV at 6, 10, and 14 weeks. RESULTS: A total of 471 subjects were randomized to the 2 study groups, and 364 subjects fulfilled the study requirements. No significant differences at baseline were detected. Thirty days after completing the 3-dose schedule of IPV, 52.9%, 85.0%, and 69.0% of subjects in the fractional-dose IPV arm seroconverted for poliovirus types 1, 2, and 3, respectively, whereas 89.3%, 95.5%, and 98.9% of subjects in the full-dose IPV arm seroconverted for poliovirus types 1, 2, and 3, respectively (all comparisons, P < .001). The median titers of each poliovirus serotype were significantly lower in the intradermal arm than in the intramuscular arm (P < .001). Only minor local adverse effects and no moderate or serious adverse events were reported. CONCLUSIONS: This large-scale evaluation demonstrates the feasibility of fractional doses of IPV given intradermally as an antigen-sparing strategy but also shows that IPV given to infants at 6, 10, and 14 weeks of age results in suboptimal immunogenicity (especially for the fractional-dose arm).

Estimating the extent of vaccine-derived poliovirus infection.

BACKGROUND: Eight outbreaks of paralytic polio attributable to circulating vaccine-derived poliovirus (cVDPV) have highlighted the risks associated with oral poliovirus vaccine (OPV) use in areas of low vaccination coverage and poor hygiene. As the Polio Eradication Initiative enters its final stages, it is important to consider the extent to which these viruses spread under different conditions, so that appropriate strategies can be devised to prevent or respond to future cVDPV outbreaks. METHODS AND FINDINGS: This paper examines epidemiological (temporal, geographic, age, vaccine history, social group, ascertainment), and virological (type, genetic diversity, virulence) parameters in order to infer the numbers of individuals likely to have been infected in each of these cVDPV outbreaks, and in association with single acute flaccid paralysis (AFP) cases attributable to VDPVs. Although only 114 virologically-confirmed paralytic cases were identified in the eight cVDPV outbreaks, it is likely that a minimum of hundreds of thousands, and more likely several million individuals were infected during these events, and that many thousands more have been infected by VDPV lineages within outbreaks which have escaped detection. CONCLUSIONS: Our estimates of the extent of cVDPV circulation suggest widespread transmission in some countries, as might be expected from endemic wild poliovirus transmission in these same settings. These methods for inferring extent of infection will be useful in the context of identifying future surveillance needs, planning for OPV cessation and preparing outbreak response plans.

A dynamic model of poliomyelitis outbreaks: learning from the past to help inform the future.

Policy-makers now face important questions regarding the tradeoffs among different strategies for managing poliomyelitis risks after they succeed with polio eradication. To estimate the potential consequences of reintroductions of polioviruses and the resulting outbreaks, the authors developed a dynamic disease transmission model that can simulate many aspects of outbreaks for different posteradication conditions. In this paper, the authors identify the issues related to prospective modeling of future outbreaks using such a model, including the reality that accurate prediction of conditions and associated model inputs prior to future outbreaks remains challenging. The authors explored the model's behavior in the context of three recent outbreaks resulting from importation of poliovirus into previously polio-free countries and found that the model reproduced reported data on the incidence of cases. The authors expect that this model can provide important insights into the dynamics of future potential poliomyelitis outbreaks and in this way serve as a useful tool for risk assessment.