A new vaccine for the avian influenza A(H5N1) was shown to be safe and immunogenic, establishing it as a needed addition to the global pool of pre-pandemic vaccines, according to a study published in Vaccine.
This Phase 2/3, double-blinded, randomized, placebo-controlled study (Clinical Trial identifier NCT02612909) conducted by the National Institute of Hygiene and Epidemiology (NIHE) in Hanoi, Vietnam, tested the safety and immunogenicity of a recently developed IVACFLU-A/H5N1 vaccine. In phase 2, researchers randomly assigned 300 healthy adults in a 1:1:1 ratio to receive placebo, a 15 mcg dose of the vaccine, or a 30 mcg dose.
Because both vaccine doses were shown to be immunogenic, the 15 mcg IVACFLU-A/H5N1 dose was selected for further evaluation in phase 3, which was conducted at 2 sites. At this stage, 105 new participants were randomly assigned into the placebo group and 525 new participants into the 15 mcg dose vaccine group (n=630). At one of the sites, 270 immunogenicity samples were taken, and 267 participants were included in the per-protocol population to assess immunogenicity.
In phase 2, the seroconversion rates were high, with 92.6% in the 15 mcg vaccine group and 93.9% in the 30 mcg vaccine group seroconverting. The IVACFLU-A/-5N1 vaccine was also well-tolerated; the majority of adverse events were mild and of short duration, with mild pain at the injection site (60% of vaccine group) being the most common adverse event. The overall seroconversion rates in phase 3 were 67.6% for hemagglutination inhibition, 55.9% for single radial hemolysis, and 51.4% for microneutralization. Seroprotection rates were 54.9% for single radial hemolysis, 44.1% for hemagglutination inhibition, and 41% for microneutralization. The geometric mean titer ratio was 5.3 for hemagglutination inhibition and 3.7 for microneutralization, and the geometric mean area for the single radial hemolysis was 4.8.
Study authors concluded, “Though more than half of the vaccinated participants did not reach seroprotection levels as per definition based on seasonal influenza, the great majority of them exhibited at least a 2-fold seroresponse level, indicative of priming. A potential approach to counter pandemic threats from A(H5N1) influenza may include priming the population with an A(H5N1) vaccine and then boosting with a dose of the pandemic vaccine at the start of a pandemic.”
Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.
Duong TN, Thiem VD, Anh DD, et al. A Phase 2/3 double blinded, randomized, placebo-controlled study in healthy adult participants in Vietnam to examine the safety and immunogenicity of an inactivated whole virion, alum adjuvanted, A(H5N1) influenza vaccine (IVACFLU-A/H5N1) [published online December 4, 2019]. Vaccine. doi: 10.1016/j.vaccine.2019.11.059