MAINTENANCE. Covid-19: variants, single dose… what will the vaccine of the future look like? An infectious disease specialist responds to La Dépêche

Nuvaxovid, Valneva… These names may not mean anything to you, but you are likely to hear about them in the years to come. At the time of the fifth wave, new vaccines against Covid-19 are emerging, either with messenger RNA, or more “classic” formulas, or even without injection, in spray… But we are entitled to ask the question: at a time when variants are regularly emerging, aren’t these new iterations already in danger of being outdated when they are marketed? Can we expect a “total” vaccine, capable of reacting to all the variants? To see more clearly, The Dispatch spoke with Christophe Rapp, infectious disease specialist at the American hospital in Neuilly.

Messenger RNA, viral vector, inactivated virus, spray or injection vaccines, it is sometimes difficult to see clearly when new types of vaccines emerge. Are some more effective than others?

Christophe Rapp, infectious disease specialist: it is true that there are beginning to exist many types of vaccines. In addition, all fall into the category of marketable vaccines, and therefore obey a certain effectiveness and a high tolerance vis-à-vis injections. However, their effectiveness may indeed be different. This is currently observed with the differences between Chinese inactivated vaccines, adenovirus vaccines and messenger RNA vaccines. For the time being, what we are sure of is that the messenger RNA is faster to produce, since the virus is not being cultivated. This is why the manufacturers who offer this type of vaccine have won the battle for the first line of vaccines with Pfizer and Moderna. Now come the “Poulidor”, more “classic” vaccines but also longer to develop. These serums are highly effective in over 70% of the population. In reality it is difficult to compare these two forms of vaccine, I believe that we do not yet have enough perspective. Marketing and documenting the effectiveness of a vaccine is feasible. Comparing them is more difficult. One thing is certain, we need all possible vaccines. Messenger RNA, as we know, is reserved for rich countries, because of the cold chain. While new vaccines will be a complement for rich countries, they will be an asset for poor countries.

Can we fear that these new vaccines will already be outdated as soon as they are marketed, due to the appearance of new variants?

That is the work of manufacturers, who constantly update their vaccines. Last year, the criterion for releasing a vaccine was above all to be effective against the initial Chinese strain of Covid-19. Then it was to be effective against the Delta variant. Today it’s about being effective against Omicron. The Omicron sub-variants that we currently have (the BA.1 and BA.2 variants, editor’s note), do not seem to have a significant impact on the response to vaccines. But will the vaccines coming out in the spring of 2022 be effective on a possible new variant? This no one can say. Still, the current vaccines, even if they were marketed a year ago, are still very effective against the Chinese strains and the Delta variant, and are a little less so against the Omicron variant.

Where is the research on “pancoronaviral” vaccines, these serums capable of responding effectively to current and future variants of SARS-CoV-2?

These projects are currently very ambitious and we lack data, because we are unable to predict the arrival of new variants. In any case, the vaccines already on the market and those coming out today are active against all coronaviruses. But it must be admitted that this is the ultimate objective to be achieved. Moreover, we have already managed to do this in the past, particularly with the case of the hepatitis C virus. Because this disease is transmitted by blood, we have succeeded in creating “pangenotypic” drugs. For vaccines, it’s much more complicated, especially for respiratory infections.

How should we be vaccinated in the future? Will a single dose be enough? Or will it be necessary, as we are doing today, to give booster shots?

There are different scenarios. The most reassuring is to consider that this virus will become endemic and seasonal in temperate countries like ours. In which case, it will be a question of making an annual reminder, in particular for the fragile people. This is somewhat the direction we are taking at the moment, letting the virus circulate and protecting the most vulnerable individuals. The bad scenario consists in thinking that we do not control the emergence of variants since the viral circulation in the world is very important and that a large part of the world population is not vaccinated. In this case, it would therefore be up to us to readjust our vaccination strategy differently by changing the composition of the vaccine and therefore being forced to start over with so-called primary vaccination regimens where we would have two doses then a booster six months later. Of these two scenarios, it is the virus that will decide, and it is very difficult to project oneself.

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