New Delhi: Earlier in August, the US Food and Drug Administration approved Moderna’s mFLUSIVA, the first ever mRNA influenza vaccine, for people 50 and older. While mRNA technology has been promoted as a faster and more flexible way, whether it actually offers better protection than existing influenza shots is yet to be seen.
Most conventional flu vaccines are made using chicken eggs or cell-based technology. Pathogens or viral seeds are grown in biological hosts such as the eggs and then once the virus has replicated, the viral material is collected, purified and deactivated.
These vaccines contain influenza antigens, proteins from the virus that the immune system can recognise. Once the vaccine delivers this protein to the immune system, it can then produce antibodies to fight off the flu.
One such protein is haemagglutinin. It is a protein found on the surface of influenza viruses and is one of the main targets of the body’s immune response.
Instead of finding a way to deliver haemagglutinin to the immune system, mFLUSIVA delivers mRNA that contains the genetic instructions to make those proteins. The mRNA is packed inside a tiny structure called lipid nanoparticles which allow the fragile substance to reach cells.
According to a phase 3 trial whose results were published in the New England Journal of Medicine, researchers gave the new vaccine to 20,350 participants and the old flu shot to 20,353 people. Of these, 2.0 per cent of the mRNA vaccine recipients developed an influenza-like illness, compared to 2.8 per cent of the standard-vaccine recipients.
A tricky virus
Influenza viruses evolve constantly and vaccine manufacturers have to keep up every flu season, because the strains circulating in one season may not be the one that dominates the next one.
In the case of traditional vaccines, manufacturers have to first select the strain, manufacture it, then distribute it. The mRNA vaccine is pitched as a more adaptable one since it can be manufactured faster and more frequently. Changing the genetic sequence in a vaccine is simpler and faster than the biological production process of the traditional vaccine.
However, it is important to note that the mRNA vaccine produces more short-term reactions like pain at the injection site, fatigue, headaches, and muscle pain which resolve within a day or two. It is also important to note that the trial shows a modest advantage and not a dramatic improvement between the efficacy of the two vaccines.