A meta-analysis study by Taiwan researchers, published in Scientific Reports on July 30, shows that aluminum salts decrease immunogenicity but increase local reactogenicity of pre-pandemic H5N1 vaccines in humans based on the significantly lower seroprotection rate after aluminum-adjuvanted H5N1 vaccines and the significantly higher risk of pain at injection sites. This research was conducted by PhD candidate Ms. Yu-Ju Lin, and her advisor, Dr. Chi-Tai Fang, professor at the Institute of Epidemiology & Preventive Medicine, National Taiwan University College of Public Health. Ms. Yu-Ju Lin is the section chief responsible for influenza pandemic preparedness at Division of Preparedness and Emerging Infectious Diseases, Centers for Disease Control and Prevention, Taipei, Taiwan. Her primary research interests are mitigation strategies for pandemic influenza.
Avian-origin H5/H7 influenza has the potential to cause the next influenza pandemic. Availability of effective vaccines is an essential part of pre-pandemic preparedness. However, avian influenza surface antigens are poorly immunogenic to humans, which necessitates the use of adjuvants to augment the immunogenicity of pre-pandemic influenza vaccines. Aluminum salts are approved, safe, and affordable adjuvants, but their adjuvanticity for influenza vaccines remains unverified, and this initiated Dr. Fang’s team to conducted this first meta-analysis on this issue.
Currently, eight manufacturers (based in China, Russia, Kazakhstan, Japan, and Australia) provide licensed aluminum-adjuvanted H5N1 vaccines. However, the World Health Organization Strategic Advisory Group of Experts (SAGE) on Immunization made the official statement that “studies using Al(OH)3 in H5 inactivated vaccines have produced variable results that are less than impressive.” To clarify the role of aluminum salts as adjuvant for pre-pandemic vaccines, Dr. Fang’s team conducted a meta-analysis of all available data reported from randomized controlled trials in human subjects.
The present study confirms an inferior seroprotection rate after aluminum-adjuvanted H5N1 vaccines compared with that conferred by non-adjuvanted counterparts. The significant decrease in seroprotection rates, as well as a significant increase in reactogenicity, indicate that aluminum salts are not suitable to serve as adjuvants for pre-pandemic influenza vaccines for human use.
[Photo: Ms. Yu-Ju Lin]