A Phase II Study Integrating a Single-Blind Safety Phase with a Double-Blind, Placebo-Controlled Randomized Phase, Assessing Single-Dose Intramuscular or Intranasal Administration to Evaluate the Safety and Immunogenicity of the Recombinant Vaccine Against COVID-19 (AVX/COVID-12 "Patria") Based on an Active Newcastle Disease Viral Vector as a Heterologous Booster in Subjects with Evidence of Previous Immunity to SARS-CoV-2.

BackgroundThe global inequity in coronavirus disease 2019 (COVID-19) vaccine distribution, primarily affecting low- and middle-income countries (LMICs), highlights the urgent need for innovative and cost-effective vaccine technologies to address availability disparities. This is crucial for achieving and sustaining widespread immunity and protecting vulnerable populations during future booster campaigns. MethodsTo address this need, we conducted a phase II clinical trial evaluating the safety and immunogenicity of the AVX/COVID-12 "Patria" vaccine as a booster dose. The vaccine was administered through both intramuscular (IM) and intranasal (IN) routes to participants who had previously received severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines based on adenoviral technology, inactivated virus, or mRNA technology. The inclusion criterion involved individuals with initial anti-spike IgG titers below 1,200 U/mL, allowing observation of the booster effect induced by vaccination. ResultsImmunization with AVX/COVID-12 resulted in a significant (>2.5 times) increase in neutralizing antibodies against the original Wuhan strain and variants of concern (VOCs) such as Alpha, Beta, Delta, and Omicron (BA.2 and BA.5). This immune response was accompanied by cellular interferon-gamma (IFN-{gamma}) production, indicating a robust and multifaceted reaction. ConclusionsThe administration of AVX/COVID-12 as a booster dose, whether through IM or IN routes, was safe and well-tolerated. The vaccine extended immune responses not only against the original Wuhan-1 strain but also against various VOCs. Its ability to enhance preexisting immune responses suggests a potential contribution to expanding and sustaining herd immunity within the population.