The vaccination rate in Germany is increasing, but at the same time the proportion of infections with the virus variant Delta. Are higher incidences threatened soon? In an interview, the immunologist Carsten Watzl explains how well the vaccines protect against Delta and why the goal of herd immunity is becoming a long way off – but that is not necessarily bad news.
Prof. Watzl, the Berlin virologist Christian Drosten currently sees Germany in a race with the delta variant of the corona virus. Who is currently in the lead: the virus or us?
At the moment it’s still us. But of course we have to keep an eye on the variant, which is shown not least by the infection rate in Great Britain, where Delta is currently leading to increasing numbers of infections. In Germany, too, the variant has increased in percentage terms in the last few weeks, but recently there has been no increase in absolute numbers with the mutant because there were fewer cases overall. We currently have very low incidences in Germany, which plays into our hands. So we now have to use the coming weeks and continue vaccinating diligently in order to protect as many people as possible.
In Germany, more than 51 percent of the population have received at least one vaccine dose so far. 32 percent are considered fully vaccinated. Are we well armed against Delta for the coming weeks?
The proportion of people who are fully vaccinated is already very good. The special thing about Delta is that after the first vaccination people are not yet well protected from infection or the disease. The second vaccination is therefore particularly important. After the second vaccination dose, the protection against serious illness increases further and is over 90 percent. The protection against infection, i.e. the disease in general, is also very good after the second vaccination dose. Astrazeneca has around 60 percent protection, Biontech around 88 percent. However, there is a certain decrease compared to other variants, because Delta can escape the immune response a little better.
How do Moderna and Johnson & Johnson compare against Delta?
No data are yet available for either vaccine. However, the vaccines from Biontech and Moderna are very similar. Both cases are mRNA vaccines. It can therefore be assumed that everything we are learning about Biontech at the moment also applies to Moderna. I would therefore expect a high level of effectiveness against the delta variant. Johnson & Johnson’s vaccine is a vector vaccine like Astrazeneca. We know from the registration studies by Johnson & Johnson that the vaccine against the beta variant, which also escapes immune protection, is quite effective. So I’m actually very optimistic about Johnson & Johnson’s effectiveness against Delta.
The corona situation in Germany is currently still good, the incidence is low. In your opinion, what measures are important besides vaccination to keep it that way for the time being?
We know that Delta is particularly contagious and we have to be careful that the variant does not lead to problems over the summer. It will be important that we do not bring too many cases into the country in the coming weeks from travelers returning or football fans who fly to European Championship games in virus variant areas. We have to test rigorously in this area. Local outbreaks should also be contained by all means available to us – from contact tracing to quarantine measures. At the moment I am still hopeful that we can manage to keep Delta down over the summer in this way.
Many tourists have taken care of vaccination protection before their trip. How exactly do we have to be with the testing?
We are currently seeing in Great Britain that it is mainly people who are infected with Delta who have not yet been vaccinated or only vaccinated once. So these are areas in which we have to be particularly careful. But we should also be vigilant if people become infected despite being fully vaccinated. These are cases that we urgently need to sequence to find out which variant is behind it. For example, it must not happen to us that a variant develops and spreads in Germany without our noticing.
Experts expect Delta to increase the number of cases towards autumn. What vaccination rate should we have achieved by then?
The higher the vaccination rate, the better. Every vaccination counts for two reasons. The first is that the person himself is initially protected from infection and illness. The second, that a high vaccination rate also serves as protection for all those who are not or not yet vaccinated.
You allude to what is known as herd immunity. However, it is questionable whether the one against the corona virus can ever be achieved.
Yes that’s true. Herd immunity means that a sufficiently large number of people have been vaccinated and that this vaccination quota ensures that even those who have not been vaccinated are protected and that the virus cannot spread. How high this threshold is, however, depends on how contagious the virus is. This is where Delta comes in again. A quick look back: we knew that the native variant of the virus had a reproductive number of around three. An infected person infected three other people without any containment measures. With the virus variant Alpha, this value increased and was between four and five. Delta is even more contagious. Here an infected person infects about five to eight people. This means that in order to achieve herd immunity against Delta, if you calculate that one person infects seven people, six out of seven people would have to be vaccinated. This corresponds to a vaccination rate of around 83 percent.
Which can hardly be achieved.
Yes, in Germany that would be almost 70 million people. So we would have to vaccinate nearly 100 percent of the adult population to get that 83 percent. We will not achieve this value. Unless we have a large percentage of children and adolescents vaccinated. But it doesn’t look like that at the moment either.
So can we say goodbye to the goal of herd immunity?
Herd immunity can hardly be achieved with the delta variant. However, that does not mean that we are running uncontrollably into a fourth wave again. As I said: every vaccination counts. And if not six out of seven are vaccinated, but maybe only four or five out of seven – and we can easily get into these areas – then that helps a lot. We can then compensate for the difference with simpler measures, for example ventilation concepts in interiors or wearing masks in local traffic. The good news is: With the vaccinations, we can get through a possible fourth wave much more easily. Without lockdown.
Biontech recently brought the possibility of third party vaccinations into play. What do you know about how long the vaccination protection lasts after a full vaccination?
The data that we have so far for the vaccinations cover the period for about half a year after the vaccination. You can see that the antibody levels drop somewhat over time, but overall it still looks okay. It can therefore be assumed that the majority of people who were vaccinated this year will get through the winter well. But there are groups where we know that the vaccination did not produce quite as high levels of antibodies. This affects older people, among other things. If it turns out now that the antibody levels in these people are also falling quite quickly, one should definitely check whether this group is vaccinated a third time in the autumn in order to have good protection during the winter.
Particularly those in need of care in the homes should then come into focus. You were vaccinated a few months ago. In your opinion, when would be the ideal time to vaccinate a third time in these vulnerable areas?
We still have some time with that. Currently we still have the situation that some people from priority group three are still waiting for a vaccination offer. If we were to start the third-party vaccinations in the homes now, it would not be effective. But late summer or early autumn would be a good time.
Last year, however, the number of infections rose in September. Isn’t it too late at the beginning of autumn to protect the homes again?
With the vaccinations we have a little more buffer this year. So one can assume that the numbers will start to rise a little later. But in October at the latest we will see that the number of infections is increasing and then at the latest we have to be careful that older, sick and particularly vulnerable people are still very well protected. This also includes people who have had organ transplants, cancer patients or people with autoimmune diseases.
Vaccine manufacturers are already working on modified vaccines that are supposed to provide even better protection against circulating variants. Will booster vaccinations with the current vaccines be enough to get through the fall and winter?
If we had a vaccine that covers the variants by fall, that would be great. But the previous vaccines also protect well. It would therefore be sufficient if we used the existing vaccines in the autumn to boost the immunity in certain groups of people. People with high antibody levels are well protected against the variants.
