Some treatments against multiple sclerosis, anti-CD20, seem to cancel the protection of vaccines against Covid-19 and increase the risk of developing a severe form, alarm specialists in multiple sclerosis before the World Day of this sickness Sunday.
Some treatments against multiple sclerosis, anti-CD20, seem to cancel the protection of vaccines against Covid-19 and increase the risk of developing a severe form, alarm specialists in multiple sclerosis before the World Day of this sickness, Sunday.
"Patients treated with this class of treatments are both more exposed to severe forms of Covid and risk responding less well to vaccination," neurologist Jean Pelletier of the Arsep Foundation told AFP (Research aid on multiple sclerosis).
According to him, "around 20%" of patients with multiple sclerosis (MS) take this type of treatment, either at the onset of their disease, or because the others have not worked.
It is estimated that more than 2.8 million people are affected by this autoimmune disease worldwide (110,000 in France).
The two drugs affected are rituximab and ocrelizumab.
Administered "in the form of infusions every six months", they are "extremely effective in the basic treatment of multiple sclerosis", according to Professor Pelletier.
But from the point of view of the Covid, it is on the other hand the double penalty.
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"Special cases"
On the one hand, the increased risk of developing severe forms of Covid has been highlighted in recent months by several studies, French, Italian and American, according to the neurologist.
On the other hand, more recently, fears have arisen concerning vaccination.
"We see people with MS and treated with these anti-CD20 who do not produce antibodies after vaccination against Covid", according to Professor Pelletier, with therefore the risk of "non-protection".
This is all the more worrying as the effect of these treatments seems "probably much more prolonged" than the six month interval they are taken.
At this stage, these observations are above all based on "special cases", but studies will reveal more.
This is particularly the case of a French study headed by Inserm and called COV-POPART.
It "aims to assess the effect of vaccination against Covid" in patients treated for several diseases (cancer, kidney disease, diabetes, MS, etc.), depending on the treatments they take.
For multiple sclerosis, 600 patients must participate, and "we will be able to have a first response in 6 months", hopes Professor Pelletier, according to whom this could make it necessary to adapt the vaccine strategy in the people concerned.
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Used in other diseases
This class of anti-CD20 is not specific to multiple sclerosis, but is used in many other autoimmune diseases such as rheumatoid arthritis, psoriasis.
It is therefore a question that goes beyond MS, ”he emphasizes.
The effects that anti-CD20 seem to cause from the point of view of Covid could be explained by the fact that these drugs act on B lymphocytes, "the cells that make antibodies", according to the specialist.
On the other hand, there is no similar signal concerning other DMARDs, such as interferons, which could even have a "slightly protective" effect, says Professor Pelletier.
Multiple sclerosis is an autoimmune disease of the central nervous system (brain and spinal cord).
It causes a disruption of the immune system, which attacks myelin, the protective sheath of nerve fibers.
"It is a disease still relatively unknown, and which one does not necessarily speak for example in his professional life", underlines the president of the Arsep Foundation, Brigitte Taittinger.
Most often, it causes inflammatory outbreaks interrupted by phases of calm. The high-dose corticosteroid treatment used to counter only these relapses (as opposed to disease-modifying treatments) could also be a risk factor for severe forms of Covid, according to Professor Pelletier.