Though mostly mild: 117,763 probable vaccine breakthroughs - infections with symptoms - have been recorded by the Robert Koch Institute (RKI) since the beginning of February, according to a weekly report Thursday evening. In view of more than 55 million fully vaccinated, experts do not see a lack of effectiveness of the vaccines, these continued to protect very well against severe courses. But in view of the fourth wave, calls are being made to offer booster vaccinations more widely.

"You have to know: Protection against infection is not as good six months after vaccination," says Bonn virologist Hendrik Streeck. Vaccine researcher Leif Sander from the Charité in Berlin explains: "The best protection is one to two weeks after the second vaccination, after which the protection against infection slowly decreases. However, vaccinated people remain significantly better protected than unvaccinated people.

The diminishing effect is not unexpected. Virologist Christian Drosten already spoke in April about the fact that vaccinated people could contribute to the transmission of the virus again after a few months. Much more important than protection against infection, however, is protection against a severe course - which remains intact, emphasizes Streeck. According to experts, those who become infected despite vaccination are generally likely to suffer a mild illness or not notice anything. In general, vaccine breakthroughs also occur with vaccinations against other diseases.

The infection can be particularly dangerous in older people or those with previous illnesses. The immune response is lower in older people after vaccination, for example, and they can then become more seriously ill. Among the total of 1076 dead Covid-19 cases with vaccine breakthroughs recorded from early February to the end of last week, 782 were at least 80 years old, according to the RKI. "This reflects the generally higher risk of death - regardless of vaccine efficacy - for this age group," it said.

The proportion of vaccine breakthroughs in all Covid 19 cases shows "that only a small proportion of hospitalized, ICU cared for, or deceased Covid 19 cases can be considered vaccine breakthroughs." The RKI calls the increase in breakthrough infections over time "expected": more and more people have been vaccinated, and the virus is spreading more again. "This increases the probability of coming into contact with the virus as a fully vaccinated person."

The Standing Commission on Vaccination (Stiko) had extended its recommendation on booster vaccinations at the beginning of October. It is aimed at people 70 and older, people with weakened immune systems, nursing home residents, caregivers, and medical personnel with direct contact with patients. People who have received the Johnson & Johnson vaccine can also boost their protection with a dose of mRNA vaccine. However, the vaccination regulation generally provides the opportunity for boosters for everyone for whom there are licensed vaccines.

Booster for all those willing to be vaccinated?

For Charité scientist Sander, the expansion would make sense in light of the Corona development: "Offering all vaccine-ready people the third vaccination six months after the second vaccination would also have a dampening effect on the spread of the virus in the population." The third vaccination could significantly improve immunity again, he said. "We would need a big campaign now for six to eight weeks as we had at the beginning of the year, with vaccination centers and mobile vaccination teams." Sander also cited the experience of Israel, where they "boosted" their way out of the past wave.

Opponents of expanding booster vaccinations, who currently include Streeck, argue, for example, that there is a global shortage of vaccines. Other countries need the doses more urgently. In addition: The health care system would be relieved more if vaccination gaps were closed for people over 60 - and less with third vaccinations for people in their mid-twenties.

Another concern is being heard from the experts: Could confidence in the vaccines suffer if there were a widespread call for boosters now? At the same time, it is clear that such a recommendation would have to come in good time, not just at the peak of the fourth wave.

Expect Corona despite vaccination

It is feared that people will again get more respiratory diseases this fall and winter. As a vaccinated person, go to the office carefree with a sore throat? Not a good idea. "Anyone who has cold symptoms in the fall and winter should get tested by PCR," Streeck says. "Even vaccinated people should consider Corona in such cases - it's a mistake to think you can't get it at all."

The risk posed by vaccinated and unvaccinated infected persons differs: "According to one study, when vaccinated persons become infected, they briefly have as high a viral load as unvaccinated persons," Streeck explained. "However, this drops much more quickly. So vaccination shortens the time period in which the virus can be passed on." And what about after a vaccine breakthrough? From Sander's perspective, no booster is likely to be needed then. "In vaccinated individuals, the infection probably acts as a booster." Sufficient data on this, however, is not yet available, he said.