A specialist in epidemic modeling claimed that certain variants less susceptible to vaccination could spread more. This could in particular occur when the French population would be immunized against the historical strain of SARS-CoV-2 and the English variant.
On April 26, 2021, Prime Minister Jean Castex was traveling to Roissy airport. On this occasion, the person concerned noted the implementation of a new protocol concerning travelers from several countries, namely South Africa, Argentina, Brazil, Chile and India. The Prime Minister had also said that the South African and Brazilian variants were very few in number and were tending to regress.
Currently in France, these variants actually represent a tiny part of contamination . On the other hand, the latter are a source of concern, just like the Indian variant which has been much talked about recently. In our country, the historical strain of the coronavirus as well as the English variant are dominant, and the current vaccines allow immunization. However, the other variants would cause immune escape, a phenomenon explained in 20 Minutes by Jean-Stéphane Dhersin, from the Analysis, Geometry and Application Laboratory (LAGA) of the University of Paris 8.
“ More there are going to be vaccinated and immunized people, the more the variants favored by immune escape will have an advantage", said the person concerned.
When asked if the Brazilian, South African and Indian variants could impose themselves in France, Jean-Stéphane Dhersin recalls first of all that the virus mutates all the time. In the case of a mutation, it becomes a question of an advantage over the previous strain. This may be a transmission advantage, due to higher virulence or longer infection duration in patients. This was particularly the case for the English variant – 1.5 times more contagious than the historical strain while the reproduction rate (R) was equal to 3.
This R is falling due to vaccination, but also due to barrier measures. On the other hand, recent variants have an advantage:immune escape . It is a question of a decrease in sensitivity to immunity acquired by disease and vaccination. In this case, the R can only fall thanks to the barrier measures. Moreover, when vaccination has achieved its objectives, the R of the English variant will drop. However, the other variants could – thanks to immune escape – be insensitive to vaccination and prevail, before becoming the source of a new outbreak of cases. According to Jean-Stéphane Dhersin, it is necessary to install an intelligent genomic monitoring plan.
The expert also claims that the increased risk of variants spreading goes hand in hand with a high incidence rate . However, viral vector sera from AstraZeneca and Janssen allow a reduction in the incidence rate. At the same time, they reduce the risk of immune escape. The sequence of events is therefore largely based on a good choice of vaccine . The other part is based on the measures taken by the authorities, how these are applied and when they will be lifted.
