Pierre Pailler: The government is awaiting the recommendations of the High Council for Infectious Diseases regarding the injection of a possible third dose to those already vaccinated. Do you think this is necessary?

Gérard Schockmel: Currently, there is already a recommendation for a third dose for immunocompromised people. In my opinion, the second group could be the elderly. The vaccine is a stimulus, but then the immune system has to kick in. Their immune systems have age-related weaknesses and are generally less responsive.

Is it possible that this third dose could be generalised?

There are discussions about a generalisation to the whole population. But I am uncomfortable with such a prospect, as a large part of the world does not yet have vaccines.

Doesn't the immune protection provided by the vaccine diminish over time?

Some studies show that protection does indeed decrease after the first six months. Other studies show different results. In any case, for healthy people, if they are vaccinated, they are not at risk. Vaccination does not prevent infection, but it is no longer a problem. Thus, infection in this case is a natural reminder for vaccinated people to develop stronger immunity, especially against mutations of the virus.

Immunity is often assessed in terms of the presence of antibodies. But there is also cellular immunity. How does it work?

Normally, the vaccine includes two aspects: the production of antibodies and the production of T cells, with the subgroup of 'killer cells'. It is the latter that constitutes cellular immunity, which is different from so-called 'humoral' immunity.

However, once a person is infected, it is not the antibodies that are most important, it is precisely these 'killer cells' that will cut short the infection by destroying the virus.

Is the duration of cellular immunity different?

The most well-characterised mutations are linked to antibodies. However, T cells often attach themselves to other parts of the spike protein [editor’s note: the key that allows the covid virus to enter our cells] and are therefore not affected by these mutations.

In addition, this cellular immunity is earlier - indeed, cellular immunity is needed to create antibodies - and has greater longevity, lasting in principle for years. Although, with the variants, the 'killer cells' can recognise the spike protein less well, which can cause a decrease in this protection.

The Delta variant is more infectious, especially in younger people. Is it not necessary to vaccinate them?

The Delta variant is more infectious for everyone, including children and younger people. But they don't get more seriously ill. Although, in absolute terms, if there are more infections, there are more serious cases.

The distinction between children and adolescents is important. Currently, vaccination is open to people over 12 years of age because the benefit/risk balance is positive. For example, there are cases of myocarditis in adolescent boys.

But there are no benefits of vaccination in children?

I don't see - this is a personal opinion - the need to vaccinate them. Vaccination is necessary for other serious childhood diseases, such as diphtheria or tetanus. But covid is not a disease of childhood.

And, from a social point of view, from the perspective of achieving herd immunity, it is not their place to be vaccinated because adults do not want to.

Even so, the virus can circulate among children and then infect adults...

Children can infect and be infected. But infants are not as infectious. And we haven't seen any major clusters in schools.

It's going to be back to school, it's going to be autumn, so people are going to be in more confined spaces, whether it's at school or in offices. Are we doing enough to avoid aerosol contamination, which was more important than we thought at the beginning of the pandemic?

Aerosols are fine infectious particles that remain airborne. So in schools, restaurants, care homes, hospitals, open spaces, it's very important to ventilate - whether it's for covid or any respiratory infection for that matter. It is a mistake to neglect this aspect. However, in Luxembourg, there has not been much interest in the subject of ventilation, the health inspectorate is dragging its feet, even though it is fundamental.

What are the methods for ensuring good ventilation of spaces?

You have to do natural ventilation by opening windows, keeping distance and [wearing] masks. When there are no windows, ventilation is necessary, with filters. There are devices on wheels. Then, real professional ventilation allows fresh air to be renewed, with a filtered part circulating again. But the installation is not easy. You also have to take into account the ceiling height and the size of the room.

Is Luxembourg now better protected against covid-19 through vaccination? Can we still envisage a wave that will saturate hospital capacities?

By accumulating vaccines and infections, we are now beginning to develop a certain immunity. So for the bulk of the population, it should go well. But there are still people who are not vaccinated.

In a year's time, Luxembourg will have a strong immunity. But this autumn we will have more cases, so more people in hospitals. So we will have to keep a close eye on the hospitals, assess the time people spend there, whether they need to be in intensive care and whether they are vaccinated or not.

And the virus is still circulating in other countries. As a member of the EU - the vaccination rate is very low in Bulgaria, for example - and as a financial centre, we will be regularly exposed to new variants.

Originally published in French by and translated for Delano