While a third dose of vaccine is currently being administered to Quebecers to deal with the highly contagious Omicron variant, many are wondering if such a booster dose will become necessary each time a new variant appears. Are we doomed to receive doses of vaccines periodically to protect ourselves against COVID-19? In the short term, it may well become necessary if new variants of concern emerge. But researchers are working to develop a universal vaccine that would protect against any variants of the coronavirus that may emerge.
“We won’t necessarily need a booster dose for every variant that emerges. It was not needed to cope with the Mu and Delta variants. If variants emerge from the same lineage as Delta and Omicron and they do not show too many changes, there is likely no need for a booster. If, on the other hand, they have mutations that make them really different from the previous ones, a booster dose of the original vaccine may be needed, as it is for Omicron. And if a variant emerges from a new line, we will probably have to resort to a new vaccine, ”says Dr.r Donald Vinh, microbiologist and infectious disease specialist at the McGill University Health Center (MUHC).
“The frequency of the booster doses that we will need therefore depends on the variants which will appear and also on the vaccines which have been developed”, underlines the Dr Vinh before recalling that for the moment, vaccines are used which mainly target the S protein of the spicules, these growths on the surface of the coronavirus which are used to attach themselves to the cells that it wants to infect. However, this S protein and its cell receptor binding domain are regions which very frequently undergo mutations liable to change the structure of the virus, which then could no longer be recognized by the cells and the antibodies generated by the acquired immunity. by vaccination or by a previous infection.
If variants emerge from the same lineage as Delta and Omicron and they do not show too many changes, there is likely no need for a booster.
“It’s likely that new variants will pop up at any time as happened with Omicron. In such a context and given that it is too early to know what will be the duration of the immunity induced by the third dose of the starting vaccine, it is possible that periodic booster doses may be required, in particular when the upsurge occurs, in the fall or in the winter for example, as we see with the flu. In the fall, a booster dose may only be needed for the most vulnerable, such as the elderly or those with chronic illnesses. Vaccines may also need to be adapted depending on the variants that will be in circulation. But these are only possibilities, because for the moment it is difficult to move forward ”, affirms for his part the expert in immunology Alain Lamarre, of the National Institute of Scientific Research (INRS).
One thing is certain, “we knew that immunity against coronaviruses is not very durable, because the immunity we acquire when we have a coronavirus cold does little to protect us against reinfection the following year. It’s pretty typical of coronaviruses, and SARS-CoV-2 is probably not much different, ”he says.
According to immunologist André Veillette, of the Montreal Clinical Research Institute (IRCM) and member of the COVID-19 Vaccines Working Group, we must wait to see if the third dose will stop the wave current product or whether a new version of the vaccine designed specifically to combat Omicron will be required to do so. “The vaccines are fantastic. People have to go get their third dose. We might need a fourth dose, but I doubt it, unless we have another surprise wave by the fall. And even if it is quiet this summer, it will be necessary to think of a dose in the fall as for the flu. It could be an mRNA vaccine more suited to the variant in circulation or a protein-based vaccine, like Novavax, which has been approved in Europe, which would stimulate the immune system differently, ”he says.
The multiple changes that the Omicron variant has undergone and which allow it to escape the protection offered by the first two doses of mRNA vaccine “show us that we really have to invest and work now on a new generation of vaccines. And new generation doesn’t mean taking Omicron’s genetic code and putting it in vaccines, which would only be an adaptation of the first generation, as Pfizer told us. We need to get out of a paradigm where we will have to give doses every six months, which does not make sense! For the moment we are doing it, we are encouraging people to go take their third dose to raise their level of antibodies which will be very useful to them in dealing with the Omicron variant. It remains that this is a strategy that is urgently justified. But in the long term, we have to find something else, ”says Dr.r Gaston De Serres, epidemiologist at the National Institute of Public Health of Quebec (INSPQ).
“We need to develop a vaccine that does not follow the evolution of the virus, as is the case for the influenza vaccine that is administered in November and December and which is composed of viruses which circulated during the previous month of February. However, the virus continued to evolve [entre février et novembre], and the one that occupies the floor in the fall is often not exactly the same as the one put in the vaccine. But many people have encountered influenza on a few occasions since birth, so they are not completely devoid of immunity to it. This immunity is far from complete protection, and that is why there are people who are hospitalized or die of the flu every year, but in proportions that have nothing to do with what they are. we see with COVID-19, ”he points out.
“It’s not easy to develop a vaccine that would be universal [qui agirait contre tous les possibles variants susceptibles d’émerger]. One thing is certain, it is probably not companies like Pfizer and Moderna that such a vaccine will come. Pfizer and Moderna used technologies that were developed as a result of many years of publicly funded research. They have been successful in using this technology to produce vaccines, we owe it to them. But the development of a new generation of vaccines will require the genius of many researchers, ”he says.
A second-generation vaccine should not target only the S protein in the spicules, which is very prone to mutations, experts warn. “Academics and companies are working to develop vaccines that target more stable proteins, that is to say less susceptible to mutations, than protein S,” notes Dr Vinh.