Filenews 26 July 2021
By Sam Fazeli
The increase in Covid-19 cases following the onset of the highly contagious Delta mutation has raised new health concerns and raised questions about the safety and pace of restarting social and economic activity, even in areas where vaccination rates are high, such as the UK.
Sam Fazeli, a Bloomberg Opinion contributor who covers the pharmaceutical industry for Bloomberg Intelligence, answers questions about the mutation and the potential threat it poses. The conversation has been edited and condensed.
The Delta mutation has caused an explosion of Covid cases, especially among the unvaccinated, but also among those who have received their vaccine. Isn't it true, however, that vaccines offer good protection, even against this mutation?
Well, the issue is slightly complicated. We knew that vaccines were never 100% effective against a corovirus infection, even before Delta's arrival.
In the trials of Pfizer-BioNTech and Moderna vaccines, for example, we saw efficacy of more than 90%, which means that very few people who had received these vaccines were subsequently tested positive for the virus. What was critical, however, was that the vaccinated individuals in these trials were 100% protected from serious illness or hospitalization.
The Delta mutation, as we will discuss below, has some characteristics that give it greater potential to cause infection, which means that it escapes the initial shield provided by antibodies. However, vaccinated individuals are still at much lower risk of developing a serious disease or, if this happens, their symptoms subside more quickly.
However, let us not cultivate illusions - some people will die from Covid-19 even if they have been vaccinated, in much lower numbers however than if they had not had the vaccine.
What makes Delta such a big threat? How does it work?
The Delta variant of the virus has developed certain mutations that make it more devastating than its "relatives". It has improved in the ability to infect cells, partly because it is able to somehow avoid antibodies in people who are already infected or vaccinated.
Once found within the cells, it is better at reproducing. The data are confirmed by the much higher amount of virus (viral load) in nasal smears of people infected with Delta compared to those observed in the first wave of the pandemic. This may come from a process called "syncytium formation", in which infected cells merge with normal cells - their "neighbours". The process helps the virus hide from the immune system and copy faster.
The Delta mutation appears to create larger clusters, which helps it create potentially more infectious copies. A higher viral load also means that an infected person can exhale more virus particles, giving them a better chance of finding their next victim. All this leads to much better "physical condition" for the virus itself, in this form.
What are the risks of getting infected while vaccinated?
Again, we have to be very careful at this point. Infections in vaccinated people are not surprising at all, since we knew from the beginning that vaccines were never 100% effective against an infection. Mutations erode their effectiveness based on this fact. The virus infects people by "lining" their respiratory tracts, otherwise known as "mucous membranes". These areas may not have as many antibodies from the vaccine, which gives the virus a small starting base. However, an infection in itself is not necessarily cause for concern for vaccinated individuals.
How serious are the cases in vaccinated people that we see? How worrying is it that even populations with high vaccination rates, such as those in Israel and the UK, see more of them?
Fortunately, we rarely see severe disease by those vaccinated, i.e. the effectiveness of vaccines against severe disease and hospitalization is still very high, regardless of each individual mutation of the coronavirus. Remember that if vaccinated people become infected, their immune system will respond and cause some of the symptoms we are used to in other infections, such as headache, clogged nose and pain in muscles and joints.
Obviously not all people are the same - some will have a much stronger antibody response to a vaccine than others and their immune system's response to an infection will also be different, which means different cold/flu symptoms. Over time, lowering antibody levels in some people who started with a weaker immune response could allow for a mild infection.
Are even mild cases in vaccinated people a worrying phenomenon?
There's a lot of issues here. One is that if you suffer a mild infection, then you can pass it on to someone who is not protected, although studies show that this transmission decreases when done by vaccinated individuals.
You also run the risk of becoming a "sponsor" of a new mutation of the virus, which will eventually make it even more effective at infecting vaccinated individuals. This is less likely, however, since viral proliferation and the duration of infection are reduced so that the virus does not have enough time to evolve towards new mutations.
An important question is whether vaccinated people with mild infections have the same risk of developing "long Covid". This is the only danger I see in a world that will accept mild Covid infections as a normal phenomenon.
Is the risk of infection of a vaccinated person higher depending on the type of vaccine he has received?
A lot of the data we have on this front comes from laboratory tests, which can tell us a little bit at the moment.
The evidence suggests that mRNA vaccines are better than so-called adenovirus vaccines, such as those of AstraZeneca and Johnson&Johnson. Real-world data comparing groups of vaccinated and unvaccinated individuals so far appears to suggest that the Pfizer-BioNTech vaccine is more effective at preventing a mild Delta infection than the AstraZeneca vaccine, based on research published in the UK.
The effectiveness of the Pfizer-BioNTech vaccine appears lower in Israel, according to data from the country's Ministry of Health, but we need much more detail to be able to assess why there is this difference between the UK and Israel. I also believe that we will find that the J&J vaccine has a lower efficacy against mild disease. The same types of analyses suggest, however, that adenovirus vaccines are equally effective against serious disease and hospitalization.
What kind of precautions should a fully vaccinated person take, knowing that the Delta mutation poses a threat?
I'll tell you what I'm doing. I wear two masks when I visit public places like supermarkets and shopping malls, where I don't know the vaccination status of people. If I go out with friends, I make sure I know who's vaccinated and who's not, so I can decide on this basis whether to go indoors or outdoors. I still don't eat indoor restaurants and avoid bars and pubs. I took a plane the other day and wore two masks, while I avoided the crowded spaces as much as possible.
Many elderly people were the first to be vaccinated in the US. Should we be concerned about weakening vaccine protection, and does the presence of the Delta mutation pose higher risks to this population?
We know that mRNA vaccines were just as effective compared to previous versions of the virus, regardless of the age of each vaccinated person. They also prevent serious diseases to the same extent. What we don't know is how Delta treats the elderly and how their immunity develops over time. That's why we have to be careful until we find out.
Is it time to start distributed booster doses of vaccines against Delta?
I think we should be prepared to do so, yes, especially if we continue to move on with our lives based on rates of mild infections. We must prepare ourselves against both Delta and Beta, a mutation first detected in South Africa. I am not sure, however, that the virus is over in terms of its evolution. Do we need booster doses right now? I don't think so. But do we have to order vaccines just in case? yes, I think we should.
What about the kids?
Children under the age of 12 are a difficult issue. The perception is that they are not at risk of serious disease from the coronavirus, which is true to some extent. However, some are sensitive to becoming really seriously ill.
In some cases, a problem referred to as multi-system inflammatory disease (MIS-C) may develop. The problem is that a lot of the data on risk to children is based on a time when we had lockdown and many people had their children attend school online, from home. Also, back then we didn't have Delta. Therefore, we run the risk of a significant increase in cases when children return to school, often without masks, in September.
Next, we have the additional problem of the rise in cases of respiratory syncytitis virus (RSV), which has decreased significantly in the last 12 to 18 months due to the use of masks and lockdowns. RSV is usually the leading cause of acute respiratory hospitalization in infants and young children, as well as in the elderly. Most infants are born with protective antibodies that are carried to them by their mother, but this is not the case for recently born newborns.
So the danger is that these children will simultaneously get RSV and Covid-19. We have no knowledge of what that would mean in terms of their health.
Source: BloombergOpinion
