Medical Research: What are the main findings of the study?
Response: A vaccine that protects against an old strain of avian flu primes the immune system to mount a rapid response when a vaccine designed to protect against a related but different and new strain of avian flu is given a year later, according to Saint Louis University research findings reported in JAMA.
In addition, when combined with an adjuvant, which is a chemical that stimulates the immune system to produce more antibodies, a lower dose of the new avian flu vaccine worked better in triggering an immune response than a stronger dose without adjuvant. That means the amount of vaccine against a new strain of bird flu can be stretched to protect more people if an adjuvant is added.
Both findings represent important strategies researchers can continue to study to fight new strains of bird flu that people previously have not been exposed to, and consequently can rapidly turn into a pandemic outbreak and public health emergency, said Robert Belshe, M.D., professor of infectious diseases, allergy and immunology at Saint Louis University and the lead author of the article, which appeared in the Oct. 8, 2014 issue of JAMA.
Medical Research: What was most surprising about the results?
Response: “People who had been primed a year ago when they received the Vietnam bird flu vaccine had developed an immunologic memory,” Belshe said. “Our findings suggest if a threat of bird flu spreading from person to person was very real, it makes sense to prime with a bird flu vaccine that is related to but does not directly match the circulating strain.”
Medical Research: What should clinicians and patients take away from your report?
Response: “This is important because of the need to respond quickly to potential pandemics. We continue to see avian flu as the possible cause of a pandemic virus in the future,” Belshe said. “Planning for influenza pandemics is of vital importance, with vaccine being a cornerstone of control efforts.”
As bird flu evolves, it could change enough to cross between species and easily spread to people whose have no pre-existing immunity to fight the new flu strain, possibly leading to a global pandemic that could kill millions.
Medical Research: What recommendations do you have for future research as a result of this study?
Response: Belshe said that those at high risk of contracting bird flu, such as certain laboratory scientists, field epidemiologists and health care workers in areas with emerging avian influenza, might consider receiving a pre-pandemic vaccine. If bird flu begins to spread rapidly, those workers could then receive a vaccination that matches the pandemic strain, theoretically triggering a quicker immune response.
“Whether priming itself has value in protecting against death is not known, but it is possible that primed individuals would have better outcomes in the face of avian flu infections,” Belshe said.
He was clear that while the study provides data to help guide pre-pandemic bird flu vaccine strategies, it is not an efficacy study.
“We do not know what amount of antibodies would be associated with protection from infection, disease or death. Each of these end points might have different correlates of protection,” Belshe said.
“The continued drift of H5 avian flu viruses means that the strain of H5 used for the boosting vaccine will need to be updated to keep pace with newer H5 bird flu viruses that emerge. Furthermore, the emergence of H7 avian influenza viruses as human pathogens will require a different priming vaccine than the H5 Vietnam vaccine used in the present study.”
Belshe also noted that because the research was limited to healthy young adults, other groups need to be studied, including older adults, adults with underlying chronic conditions, pregnant women and children, since their dose and safety profiles might differ.