Immunogenicity and safety of an adjuvanted inactivated polio vaccine, IPV-Al, following vaccination in children at 2, 4, 6 and at 15-18 months

Safety, tolerability, and immunogenicity of inactivated poliovirus vaccine with or without E.coli double mutant heat-labile toxin (dmLT) adjuvant in healthy adults; a phase 1 randomized study

BACKGROUND

Inactivated trivalent poliovirus vaccine (IPV) induces humoral immunity, which protects against paralytic poliomyelitis but does not induce sufficient mucosal immunity to block intestinal infection. We assessed the intestinal immunity in healthy adults in Belgium conferred by a co-formulation of IPV with the mucosal adjuvant double mutant Labile Toxin (dmLT) derived from Escherichia coli.

METHODS

Healthy fully IPV-vaccinated 18-45-year-olds were randomly allocated to three groups: on Day 1 two groups received one full dose of IPV (n = 30) or IPV + dmLT (n = 30) in a blinded manner, and the third received an open-label dose of bivalent live oral polio vaccine (bOPV types 1 and 3, n = 20). All groups received a challenge dose of bOPV on Day 29. Participants reported solicited and unsolicited adverse events (AE) using study diaries. Mucosal immune responses were measured by fecal neutralization and IgA on Days 29 and 43, with fecal shedding of challenge viruses measured for 28 days. Humoral responses were measured by serum neutralizing antibody (NAb).

RESULTS

Solicited and unsolicited AEs were mainly mild-to-moderate and transient in all groups, with no meaningful differences in rates between groups. Fecal shedding of challenge viruses in both IPV groups exceeded that of the bOPV group but was not different between IPV and IPV + dmLT groups. High serum NAb responses were observed in both IPV groups, alongside modest levels of fecal neutralization and IgA.

CONCLUSIONS

Addition of dmLT to IPV administered intramuscularly neither affected humoral nor intestinal immunity nor decreased fecal virus shedding following bOPV challenge. The tolerability of the dose of dmLT used in this study may allow higher doses to be investigated for impact on mucosal immunity. Registered on ClinicalTrials.gov - NCT04232943.

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.

Persistence of protective anti-poliovirus antibody levels in 4-year-old children previously primed with Picovax®, a trivalent, aluminium-adjuvanted reduced dose inactivated polio vaccine

Background

To meet the demand for effective and affordable inactivated polio vaccines (IPVs), a reduced dose, aluminium hydroxide (Al(OH)₃)-adjuvanted IPV vaccine was developed (IPV-Al, Picovax®) and evaluated in clinical trials. The present trial is an extension of two previous trials (a primary and a booster trial). The aim was to evaluate the persistence of seroprotective antibodies (poliovirus type-specific antibody titre ≥ 8) in 4-year-old children who previously received IPV–Al as primary and booster vaccine doses and to determine the potential booster response and safety profile of an additional dose of IPV-Al.

Methods

Children participating in the two previous trials were invited to receive one additional dose of IPV-Al at 4 years of age (2.5 years after the booster dose) and to have their blood samples collected to measure the pre- and post-vaccination antibody titres. Systemic adverse events (AEs) and local reactogenicity were recorded.

Results

At study entry, the seroprotection rates were 89.2%, 100% and 91.1% against poliovirus type 1, 2 and 3, respectively. The additional vaccination with IPV-Al boosted the level of poliovirus type 1, 2 and 3 antibodies to above the seroprotection threshold for all but one subject, i.e., 99.4% for type 1 and 100% for types 2 and 3. The additional dose induced a robust booster response of a 26.3-, 13.9- and 30.9-fold increase in titre for poliovirus types 1, 2 and 3, respectively. The vaccine was well tolerated, with only mild and transient AEs reported.

Conclusions

The present trial demonstrated that the primary vaccination with an aluminium-adjuvanted reduced dose IPV induced a persistent immune memory as evidenced by the robust anamnestic response when the subjects were re-exposed to the antigen 2.5 years after the last dose. Thus, the IPV-Al is an efficient and safe addition to increase the availability of inactivated polio vaccines globally. (ClinicalTrials.gov reg no. NCT04448132).