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The vaccines also protect against the delta variant of the coronavirus, but the effectiveness is said to be reduced, just below 90 percent. What does that mean, are 10 percent of those vaccinated unprotected, is each individual 90 percent protected, or does it mean something completely different?
While all other corona virus variants are in retreat, the delta mutant (B.1.617.2) is spreading rapidly. The European Centre for Disease Prevention and Control (ECDC) estimates in its threat report that delta will reach 90 percent across Europe by the end of August.
Delta pushes protective efficacy below 80 percent
Based on its own preliminary study, the U.K. Public Health Agency (PHE) estimates 80 percent protection against symptomatic disease in fully vaccinated individuals, down from 88 percent with the alpha variant. With just one dose, protection drops to about 30 to 40 percent.
Chicago Health Chief Allison Arwady said yesterday that according to a recent study, the effectiveness of Pfizer/Biontech’s mRNA vaccine against the delta variant was 84 percent. According to a Scottish study published June 14, the vaccine is actually only 79 percent effective against Delta. Pfizer’s medical director, Alon Rappaport, on the other hand, recently said the vaccine is about 90 percent protective against corona disease from the variant.
Fewer antibodies in the blood
Moderna published its own preliminary study Monday showing that its mRNA vaccine has 2.1 to 3.2 times fewer neutralizing antibodies (titers) compared with wild-type at Delta. The manufacturer thus bypasses a percentage efficacy figure, but writes in its press release that it is only a “moderate reduction.”
Based on a long-term study by London’s University College, however, Moderna’s vaccine, like the Biontech and Pfizer vaccines, appears to have retained a high level of protection. According to the “legacy” study, that vaccine reduced the number of antibodies in the blood by 5.6-fold. The Moderna vaccine thus protects at least as effectively against the delta variant. The reduction in titers is probably the reason why two doses are needed for a good protective effect. This compensates for the lower number of antibodies formed.
The situation is not so good with the vector vaccine from Astrazeneca. According to the “Legacy” study, antibodies could only be detected in 62 percent of those fully vaccinated, whereas 95 percent of those vaccinated with the Biontech product were.
In a press release, however, Astrazeneca points to another preliminary PHE study that says the vaccine provided 92 percent protection against severe illness with hospitalization, even with the delta variant after the second dose. It also said there was not a single death after full vaccination.
Protection against severe course remains very high
This hits the nail on the head, because that is what vaccinations are all about: avoiding severe courses and deaths. But at the same time, Astrazeneca is also playing a bit of a trick to increase the percentage figure. In terms of vaccine efficacy, the mRNA vaccines from Biontech/Pfizer and Moderna are still somewhat better, with Biontech achieving 96 percent in the PHE pre-study.
But comparing vaccine efficacy based on percentages is difficult anyway. It starts with the fact that many people don’t know what the stated efficacy is all about when the substances are approved.
It’s all about risk
If a vaccine is 90 percent effective, this does not mean that only 90 percent of those vaccinated are protected and the other 10 percent have received two injections in the upper arm for nothing. 90 percent efficacy means that for all those fully vaccinated, the risk of contracting disease symptoms is reduced by this value compared to unvaccinated individuals.
To determine the protective effect, study participants (phase 3) are divided into two equally sized groups. In the case of the Biontech vaccine, for example, there were 43,500 people between the ages of 12 and 91. One half is vaccinated, the other receives a placebo. After a certain period of time, it is determined how many of the respective group fall ill. This also includes completely harmless courses; every infection counts. 90 percent effectiveness means that the group of vaccinated people had 90 percent fewer cases than the unvaccinated group.
Values hardly comparable
The vaccine percentages are not comparable for two different reasons: First, all vaccines would have to be tested on the same study participants. Second, the conditions would have to be the same. Among other things, the studies took place at different times in different parts of the world.
“It’s going to be difficult with herd immunity”.
It is now similarly difficult to precisely determine the reduced effect in the delta variant. However, it is important to note that a decrease from 95 to 90 or 80 percent is not a catastrophe. After all, all it means is that there are more infections. But as the PHB preprint used by Astrazeneca shows, the vaccines still protect very well against hospitalization after the second vaccination, and all three reduce the risk of severe disease by more than 90 percent. And even if it happens, the risk of dying in the hospital is extremely low.
More infections despite double vaccination
However, a reduced protective effect means that the principle of considering all vaccinated people as completely immunized no longer applies with the delta variant. Too many of them can still become infected and continue to carry the virus. This is currently seen above all in Great Britain, where the delta variant has already reached a share of almost 100 percent. Almost 50 percent of the British population has already been vaccinated twice, but the number of cases is rising rapidly and the 7-day incidence is again above 200.
— Source: ntv.de/picture: dw.com
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