Due to the lack of hindsight, it is difficult to establish the virulence of the omicron variant at the moment. But in any case it represents a definite threat due to its very high contagiousness (305 to 50% more transmissible than the delta variant), says Gérard Schockmel, consultant physician in infectious diseases at the Robert Schuman Hospitals (HRS). Its numerous mutations reduce the protection conferred by vaccination, even if a third dose makes it possible to increase protection again, whether against infections or severe forms of illness.
With the hindsight we now have, what do we know about the omicron variant?
Gérard Schockmel: What we can say with certainty is that the omicron variant is more contagious. It is 30% to 50% more transmissible than the delta variant, which was already the champion in this respect. In South Africa, the UK and Denmark, for example, the number of cases doubles every two to three days.
The current problem remains the delta variant. But we will see how quickly omicron will replace delta. In Europe, the omicron variant is expected to become dominant within a few weeks, although this is still an extrapolation.
But is this omicron variant more likely to cause severe forms of illness?
Complications take some time to develop, so we haven’t had enough time to see--only three weeks in South Africa. In addition, the population in South Africa is young and has some immunity, as many of them have already been infected or vaccinated. So this may give the impression that the virus is less virulent.
But, in absolute terms, it’s more complicated, because you would have to compare groups of unvaccinated people infected, in one case, with delta, and, in the other, with omicron. But we don’t have that anymore, because many people in a community are now immune through vaccination or infection.
There will be more cases, and therefore more people with complications.
But the current trend seems to be towards a lower virulence of the omicron variant...
If we assume that the omicron variant is less virulent, it is still highly transmissible. So there will be more cases, and therefore more people with complications. The question is who will be affected.
The most vulnerable people are the unvaccinated. Many unvaccinated people will have complications, even if the variant is less virulent. So, it is in their interest to get vaccinated. There is also the group of people who have been infected with covid. For them too, the antibodies fade over time, and for them too, the recommendation is to get vaccinated.
What about vaccinated people? The many mutations in the omicron variant seem to affect the effectiveness of vaccines.
For those vaccinated with two doses, immunity is indeed lower against omicron. In the UK, current figures show 40% protection against infection a few months after the second dose and 70% against severe illness.
But the good news is that with a third dose, protection against infection rises to 80%. And there is every reason to believe that protection against severe forms also increases--although this is difficult to measure--and that it lasts longer.
With a third dose, protection against infection rises to 80%. And there is every reason to believe that protection also increases against severe forms.
Protection against severe forms of the disease is still important. Why is that?
There are two lines of defence: the first, called humoral immunity, is conferred by antibodies and is effective against infections. This immunity fades quickly over time.
Then there is a second line of defence: cellular immunity, which is effective against severe forms. It works mainly with T-cells, of which the “killer cells” are a part. Once a person is infected, the antibodies are no longer very effective, because it is the killer cells that will destroy the infected cells. But this immunity does not fade so quickly.
For example, a person who has received two doses of the vaccine is currently 40% protected against infection by antibodies, but 70% protected against serious complications by cellular immunity.
The first and second doses were very close together--too close to create long-term immunological memory. But the aim then was to provide maximum immunity in a short period of time.
In addition, the omicron variant is characterised by numerous mutations. But these mutations mainly concern the attachment sites of the antibodies. Killer cells do not necessarily attach to the same place, so they are less affected by these mutations.
The government recently reduced the window to receive the third dose from six to five months after vaccination. This is expected to be reduced to four months at the beginning of next year. How long does the third dose take to be most effective?
More time between the first two doses would have resulted in better immunity and immunological memory. At the beginning of the vaccination campaign, the first and second doses were very close together--too close to create long-term immunological memory. But the aim then was to provide maximum immunity in a short period of time, because when infections flare up, there is an emergency.
On the timing of the third dose, the European Medicines Agency (EMA) has already discussed a three-month delay. I would advocate flexibility. But it is important not to lose sight of the most vulnerable people, who must remain a priority.
The virus is not going to go away. But we are going to get through it collectively, because immunity builds up from wave to wave.
Aren't the side effects of the third dose stronger?
It varies. Some people reacted more strongly to the third dose. Others tolerated it better than the first and second doses. There is no uniform rule.
Will a fourth dose be necessary? And if so, when?
We don’t know yet. Cellular immunity has a long lifespan in general. But how effective will it be against new variants? In all likelihood, the fourth dose will be made with vaccines that have already been adapted and tailored to the new variants. But these new vaccines will not be available for a few months. So don't wait for the third dose.
The appearance of this new omicron variant seems to make an already precarious situation worse. Other variants will appear. Is there a way out of the crisis?
The virus is not going to disappear. But we are going to get through it collectively, because immunity is created from wave to wave. The new variants will therefore circulate in populations that have already acquired partial immunity. In absolute terms, they will not be less virulent. But their effects will be progressively less important at the level of the community as a whole.
If compulsory vaccination had been applied in the spring, we would not be in a crisis situation this winter.
The number of cases is exploding in Europe as the festive season--a sensitive time as people gather--approaches. What advice do you think would be useful?
The most urgent thing is for people who are not vaccinated to get vaccinated. That those who are eligible get their third dose. And that previously infected people get vaccinated as well, because more and more studies are showing that they need a full vaccination regimen, too.
Do you think the government’s health measures are appropriate to the situation?
If compulsory vaccination had been implemented in the spring, we would not be in a crisis situation this winter. The political calculation was clear: avoid compulsory vaccination in order not to make yourself unpopular. But this did not work. On the contrary, it has created a division in society, between the vaccinated and the non-vaccinated. Compulsory vaccination is an egalitarian measure aimed at civil and social equality. But our governments still lack the necessary courage. It is an endless procrastination.
This story was first published in French on . It has been translated and edited for Delano.