Immunogenicity to poliovirus type 2 following two doses of fractional intradermal inactivated poliovirus vaccine: A novel dose sparing immunization schedule

Abstract

Introduction: The polio eradication endgame strategic plan calls for the sequential removal of Sabin poliovirus serotypes from the trivalent oral poliovirus vaccine (tOPV), starting with type 2, and the introduction of ≥1 dose of inactivated poliovirus vaccine (IPV), to maintain an immunity base against poliovirus type 2. The global removal of oral poliovirus type 2 was successfully implemented in May 2016. However, IPV supply constraints has prevented introduction in 21 countries and led to complete stock-out in >20 countries.

Methods: We conducted a literature review and contacted corresponding authors of recent studies with fractional-dose IPV (fIPV), one-fifth of intramuscular dose administered intradermally, to conduct additional type 2 immunogenicity analyses of two fIPV doses compared with one full-dose IPV.

Results: Four studies were identified that assessed immunogenicity of two fIPV doses compared to one full-dose IPV. Two fractional doses are more immunogenic than 1 full-dose, with type 2 seroconversion rates improving between absolute 19-42% (median: 37%, p<0.001) and relative increase of 53-125% (median: 82%), and antibody titer to type 2 increasing by 2-32-fold (median: 10-fold). Early age of administration and shorter intervals between doses were associated with lower immunogenicity.

Discussion: Overall, two fIPV doses are more immunogenic than a single full-dose, associated with significantly increased seroconversion rates and antibody titers. Two fIPV doses together use two-fifth of the vaccine compared to one full-dose IPV. In response to the current IPV shortage, a schedule of two fIPV doses at ages 6 and 14weekshas been endorsed by technical oversight committees and has been introduced in some affected countries.

Keywords: Fractional inactivated polio vaccine; Inactivated polio vaccine; Polio immunogenicity; Priming.

Fig. 1.

Reverse cumulative poliovirus antibody distribution curves for type 2 poliovirus. Footnote: Panel A: Cuba 1 [15]; Panel B: Oman [17], Panel C: Cuba 2 [7]; Panel D: Bangladesh [16]; and Panel E: India [18].

Fig. 2.

Sri Lanka and, States and Territories of India which have, or will introduce in 2016–2017 a two-dose fIPV routine immunization schedule for poliomyelitis prevention.