Safety and immunogenicity of Thailand Government Pharmaceutical Organization (GPO) produced, COVID-19 vaccine, 10 μg HXP-GPOVac: A Phase III, double-blind, randomized trial in comparison with VAXZEVRIA
Year: 2026
Type: article
Study designs: Randomized Controlled Trial, Clinical Trial
Abstract: Background HXP-GPOVac is a Thailand-produced, egg-based, inactivated recombinant Newcastle disease virus (NDV)-chimera vaccine expressing a membrane-anchored, prefusion-stabilized SARS-CoV-2 spike (NDV-HXP-S), developed to expand vaccine access. This phase III trial evaluated the safety and immunogenicity of a single HXP-GPOVac dose in healthy or clinically stable Thai adults who had completed a two-dose primary series of an authorized COVID-19 vaccine. Methods In this double-blind, randomized, active-controlled trial in Nakhon Phanom, Thailand, 4000 participants were randomized 3:1 to receive HXP-GPOVac or VAXZEVRIA (AstraZeneca, ChAdOx1 nCoV-19). Safety outcomes included incidence, severity, and vaccine-relatedness of adverse events (AEs). AE incidence was compared between vaccine groups using Chi-square or Fisher's exact test. Immunogenicity was assessed by pseudovirus neutralization assay for 50% neutralizing antibody titers (NT 50 ) and ELISA for anti-Spike IgG. Non-inferiority was prespecified for NT 50 -based endpoints at day 14, defined by (i) a geometric mean concentration (GMC) ratio (HXP-GPOVac/VAXZEVRIA) with 95% CI lower bound >0.67 and (ii) a seroconversion rate (SCR) difference with 95% CI lower bound > −10%. Results Solicited AEs occurred in 43.7% of HXP-GPOVac recipients versus 53.5% of VAXZEVRIA recipients ( p = 0.01). Most solicited AEs were mild. No vaccine-related serious AEs were reported. At day 14, the NT 50 GMC ratio (HXP-GPOVac/VAXZEVRIA) was 0.83 (95% CI lower bound: 0.74), and the SCR difference was −2.35% (95% CI lower bound: −8.72%), both meeting non-inferiority criteria. Conclusion HXP-GPOVac was well-tolerated and demonstrated non-inferior immunogenicity compared with VAXZEVRIA at 14 days after vaccination. These findings provide rationale for larger studies to assess HXP-GPOVac clinical efficacy.
Source: Vaccine
Authors: Kriengkrai Prasert, Sutthichai Nakphook, Jiraphut Kittiwatanachod, Darunee Ditsungneon, Kanlaya Sornwong, Suriya Naosri, Ponthip Wirachwong, Isariya Techatanawat, Piengthong Narakorn, Somchaiya Surichan, Jorge Flores, Laina D. Mercer, Christina S. Polyak, Bruce L. Innis, Rama Raghunandan, Chakrarat Pittayawonganon, Sopon Iamsirithaworn, Supakit Sirilak, Colleen Scott, Martha P. Montgomery, William W. Davis, Prabda Praphasiri
Language: English
Subfield: Infectious Diseases
Field: Medicine
Domain: Health Sciences
Open Access status: hybrid
Estimated APC paid: $3,620
OpenAlex ID: W7221552247