British researchers have chosen a different approach for a new anti-Covid vaccine, which will be delivered by means of a skin patch.
We are now officially in the middle of the fifth wave, and the pandemic unfortunately continues to weigh heavily on Europe and even the world. But even if immunization coverage continues to increase, the question of the duration of immunity is still hotly debated. In an attempt to provide more guarantees at this level, an English company has just launched a clinical trial for a second generation vaccine; administered via a skin patch, it would offer longer immunity compared to current solutions.
These patches are based on a concept initiated in 2016 by Thomas Rademacher, professor of molecular medicine at University College London. It was he who had the idea to adapt to Covid a type of vaccine entirely based on a central player in the immune system: T lymphocytes. Once injected, gold particles coated with peptides contained in the patch allow to put these lymphocytes in working order; in essence, it amounts to recruiting them and ordering them to get rid of the infected cells.
“This is the first time that a regulator has approved a clinical trial for a Covid vaccine whose sole objective is to generate a targeted T cell response in the absence of an antibody response, by directly targeting infected cells”, Explains Robin Cohen, spokesperson for the firm interviewed by the Guardian.
This is quite different from the messenger RNA vaccines produced by AstraZeneca / Oxford or Pfizer / BioNTech. These also induce a reaction on the side of the T lymphocytes, but to a lesser extent; they are based above all on a global immune response based on antibodies. This method is very effective in neutralizing SARS-Cov-2; but this requires maintaining this protection at a sufficient level, which implies booster shots.
A supplement rather than a full-fledged vaccine?
The more aggressive solution proposed by this team would make it possible to obtain a much longer immunity, potentially of the order of ten years. But not all specialists are so categorical. Danny Altmann, professor of immunology at Imperial College London who was not involved in the study, doubts, for example, that this method will be sufficient on its own. But that does not mean that it would be devoid of interest.
Antibodies are very specific sentinels, and each type is only compatible with a specific target. This makes them very sensitive to mutations, which potentially limits their effectiveness on future variants. T cells, on the other hand, are much more versatile and could work on a larger set of targets. It could therefore be a good supplement, especially in cases of acute Covid.
Another advantage of this method: since it is a patch, it can be applied yourself without needing a professional for the injection. In addition, the vaccine could be stored in this form for three months at room temperature. A considerable logistical advantage, knowing that standard vaccines must be refrigerated.
This vaccine will be tested from next January in Lausanne, Switzerland. On the other hand, we will have to wait a little longer to see it arrive on the market. The clinical trial is expected to last approximately three years; if it is successful, we could therefore see the first anti-covid patches arriving around 2025.