Several French biotechs are working on vaccines that would be effective for several years against mutations in the coronavirus. (Drawing) – Michel Euler / AP / SIPA
As we know, the Covid-19 virus mutates (just like the flu, for example). Therefore, researchers will have to regularly update the vaccine against the coronavirus so that it continues to be effective in the face of mutations (again as with the flu vaccine). Are anti-Covid vaccines therefore doomed to quickly become obsolete in the face of virus mutations? Not so sure.
Some start-ups are currently working on vaccines that would be effective in the long term on the various mutations of the virus. “It could protect over several years,” says Alexis Peyroles, boss of OSE Immunotherapeutics, about a vaccine project for which this French start-up has just started the first clinical trials.
How effective will the vaccines currently being administered remain?
The promise is a vaccine that resists the appearance of variants, new strains of the coronavirus that differ from those from which the first vaccines were developed. This is one of the current great unknowns of the epidemic: to what extent will the vaccines currently administered, like that of the American Pfizer, remain effective when these variants multiply?
So far, they seem to be holding up well but the boss of Pfizer himself, Albert Bourla, recently deemed it likely that he would have to inject a new – updated – dose of his vaccine every year.
Focus on the immune response rather than the production of antibodies
Faced with this challenge, several biotechs are following a different path from current vaccines: they seek to first stimulate T lymphocytes, namely the part of the immune response which focuses on the detection and elimination of already infected cells, instead of focusing on the virus itself.
The vaccines in circulation, on the other hand, first aim at the production of antibodies, which recognize and destroy the virus directly, before it infects a cell. This does not mean that these vaccines do not induce any T cell response – the first data is rather encouraging – but it is not their priority angle of attack. However, T lymphocytes theoretically have several advantages over antibodies. They can survive longer in the body and respond to components of the virus that are much less likely to mutate than those detected by antibodies.
Isolated projects
In France, the track of the “T response” is followed by OSE and a competitor from Lyon, Osivax, which even promises a “universal” vaccine, that is to say ready to respond to any potential variant. The state has granted them millions of euros in funding, while France is behind in the development of an anti-Covid vaccine.
These projects are isolated because few laboratories believe in a universal vaccine. Of the nearly 400 anti-Covid vaccine projects identified by the World Health Organization (WHO), only a few claim this perspective. The most advanced is that of the American ImmunityBio which published last month rather encouraging results but still very preliminary.
A double-edged weapon “
Because the reality of these vaccines is still very uncertain. None of the groups concerned promises one before next year and many scientists doubt that this lead will succeed. Some wonder whether it is not illusory to seek to respond in advance to the future emergence of new strains. “When there is a mass vaccination, it is in itself (…) a pressure which can lead the virus to evolve so as to escape the vaccine, whatever it is”, warns the British virologist Julian Tang, who sees therefore a “double-edged sword” in vaccines designed to brew very broad.
The other big question is to what extent our organism will resist the virus if we prepare its response rather by T lymphocytes. “I am doubtful as to the effectiveness of such a vaccine”, estimates the French virologist Yves Gaudin. Lymphocytes and antibodies work in tandem. If the antibody response is not well in place, the T cells “will not be of much use,” he insists, stressing that the ideal is a vaccine that is effective on both levels.
Protection for people with cancer and diabetes
But, precisely, if these new vaccines become reality, they will be injected, at least in Europe and the United States, to people who have already received the current vaccines. Their antibodies will therefore be prepared. This is the argument used by Alexis Peyroles at OSE Immunotherapeutics to ensure that his vaccine, in the event of positive results, will find its place.
With this vaccine, “you complete and broaden, on the breadth and duration, the defense developed thanks to the initial vaccines,” he says. He also argues that such a vaccine would offer protection to individuals who naturally struggle to develop antibodies, for example because they have certain cancers and diabetes.