One dose of a synthetic year-round flu vaccine that provides long-lasting protection against two of the most common types of influenza infection could be on the horizon, according to the results of early clinical trials.
Each year, the flu infects millions of people around the world, resulting in an estimated 3 to 5 million severe cases. Of those, between 290,000 and 650,000 people will die due to associated respiratory issues, according to the World Health Organization (WHO).
Described in the Annals of Internal Medicine, researchers write that the newly devised FLU-v vaccine can be produced and administered throughout the year and protect against both A and B influenza strains. Viruses, such as H1N1, are capable of infecting animals and spreading to humans. On the other hand, B viruses are found only in humans and often spur a less severe reaction than the former, according to the Centers for Disease Control and Prevention (CDC).
Producing a universal year-round vaccination has proven difficult because influenza viruses mutate quickly, requiring a new vaccination every year with inactivated or attenuated viruses. Currently, medical experts will wait to see which strains are the most likely to be virulent in a given year and try to target the top four most likely to result in widespread infections. Manufacturing can be a lengthy process and the short time between WHO recommendations and when the flu season starts means that the availability of flu vaccines can be limited. Additionally, there is a possibility that predictions identified the wrong strain or it could have evolved by the time vaccinations are distributed.
In the phase 2b clinical trial, which compares the safety of different formulations and doses but not the efficacy, an international team of researchers with the Universal Influenza Vaccines Secured, a European Union-funded consortium advancing universal influenza vaccines, randomly assigned 175 healthy adults between 18 and 60 years old to receive either one dose of an adjuvanted FLU-v or two doses of nonadjuvanted. Adjuvants are ingredients used in some vaccines to help boost the immune response to the vaccination, according to the CDC. Cellular responses were assessed at 42 and 180 days later, while feedback from study participants was collected throughout the study. Throughout the double-blind, placebo-controlled trial study participants were tested for influenza infection and asked to report on any symptoms daily.
A single dose of FLU-v showed a greater immune response compared with the placebo. As well, researchers found adverse effects were mostly mild to moderate at the injection site.
The team adds that a phase 3 trial is warranted to further explore the efficacy of the FLU-v vaccination.