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

Abstract

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).

Keywords: Affordable inactivated polio vaccine; Aluminium hydroxide adjuvant; Immunogenicity; Oral polio vaccine; Polio; Reduced dose.

Conflict of interest statement

Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Copyright © 2022. Published by Elsevier Ltd.

Figures

Fig. 1

Flowchart of patients enrolled in the trial. 167 subjects were screened for eligibility. 163 were enrolled and received the trial vaccination (safety analysis set, SAF). Five subjects were excluded from the full analysis set (FAS), and three subjects were excluded from the per protocol analysis (PP) due to protocol deviation. 162 subjects completed the trial and 1 discontinued. The analysis sets were 163 subjects for SAF, 158 for FAS, and 155 for PP.

Fig. 2

Reverse cumulative titre distribution for type 1 (A), 2 (B) and 3 (C) antibody titres following primary, booster and additional vaccination with IPV-Al (PP). Data from primary (VIPV-07) and booster (VIPV-07-E1) trials illustrate only subjects who participated in the present extension. Subjects received IPV-Al as primary, booster and additional vaccination, and had their blood collected at 4 years of age during visit 1 (pre-vaccination) and visit 2 (post-vaccination) of the present trial (VIPV-07-E2). Each figure includes six curves, a pre-booster (V1) solid line and a post-booster vaccination (V2) dotted line for each group. Analysis set: per protocol.