Virologists sound the alarm: delta variant also spreads via vaccinated people
Once again, virologists are sounding the alarm about the coronavirus. The delta variant is so contagious that people who have already been fully vaccinated can also pass on the virus. This could have ‘major consequences’ for policy, the scientists warn.
Although vaccinees who contract the delta variant usually do not become so sick that they end up in hospital, they can transmit the virus to others. That is why people who have been vaccinated should adhere to the same rules as those who have not been vaccinated: testing immediately in case of complaints, testing for admission tickets and after returning from vacation, and keeping an extra good distance from people who have not yet been vaccinated.
“The idea we had in the beginning, that you no longer transmit the virus after vaccination, does not seem to hold true for the delta variant,” says clinical virologist Matthijs Welkers (Amsterdam UMC). “We even see people who have already had an infection, have been vaccinated twice and are now testing positive again.”
Health care workers positive
In recent weeks, Dutch hospitals have been startled by a sharp increase in the number of fully vaccinated employees who still turn out to be positive. In Amsterdam it concerns ‘dozens’ of employees, at the LUMC 85 percent of all positively tested employees have been fully vaccinated, at the Radboud UMC 34 cases were recently turfed.
Intensive care in Tilburg. Statue Marcel van den Bergh
It is mainly the ‘mega-high’ number of virus particles that stands out, says medical microbiologist Heiman Wertheim (Radboud UMC), who just happened to test positive himself. “We really thought, what is this? If you extend this to the rest of society, you have quite a big problem.’
After all, vaccinees who contract the virus usually have few complaints themselves. “I think you have a significant group of vaccinated people who just go through with it,” Wertheim says. "I probably would have done that myself, if I hadn’t happened to test myself. Somewhere you think: I’m vaccinated, I’m okay now. But you can still pass the virus on.”
What probably happens is that the virus partially undermines the immune system. Anyone who becomes infected with the delta variant produces up to a thousand times as many virus particles as with the original variant, according to a recently published analysis. “At the beginning of the infection, it’s probably so much that your antibodies can’t keep up,” says Welkers. “Because of its large numbers, the virus breaks through the defense as it were.”
In addition, antibodies from vaccinees are about eight times less effective on the delta variant protrusions than on those of the original virus, recently published British lab tests show. That doesn’t make things any better.
The fact that vaccinated individuals rarely end up in ICU or die is due to something else. After the initial phase of the infection, the delta variant probably also runs into the T cells, the line of defense that cleans up affected cells and controls the inflammation. This keeps the disease limited.
It was to be expected that some vaccinated people would become infected again, says virologist Marion Koopmans (Erasmus MC) when asked, because vaccines do not fully protect. “But with the delta variant, that story is even sharper.”
Koopmans also prefers to get rid of the preferential position of vaccinated people. "Actually, at this stage, if it could be organised, you would want to test everyone as much as possible, to keep an eye on the virus. In any case, it is wise to get tested when you return from vacation or if you have minor complaints, even if you have been fully vaccinated.’
Statue Marcel van den Bergh
In other countries, that awareness is also beginning to decline. For example, Israel, where the population was vaccinated with the Pfizer vaccine, announced on Friday that more than a thousand fully vaccinated people in that country have already become infected with the delta variant again. And in India, scientists discovered that healthcare workers who had been vaccinated with AstraZeneca often still became infected with the delta variant. “The warning that this emanates is that although vaccination is very important, it is not the only thing that is needed to prevent transmission,” says Koopmans.
The discovery of the infections is a strange echo from a year ago. When corona was new, it was also discovered that the virus spread under the radar by testing sniffling healthcare workers. Many of them turned out not to be a common cold, but the coronavirus among