How much does the vaccination really decrease?

The vaccination against SARS-CoV-2 is still the most effective weapon we have against the corona pandemic. The available mRNA vaccines protect people who have been vaccinated by over 90 percent from severe courses of Covid-19. However, this protection diminishes over time, which leads to a significant increase in vaccination breakthroughs – for this reason, booster vaccinations are currently also recommended. In a study with over 80,000 vaccinated test subjects in Israel, the researchers were able to gain a more detailed insight into the course of the decrease in vaccination protection.

Photo: Syringe With 2 Drops, ZaldyImg, Flickr, CC BY-SA 2.0

Investigations in Israel

In combination with the significantly more infectious delta variant of the SARS-CoV-2 virus, a decrease in vaccination protection is dangerous. Over time, fewer antibody cells specific to the virus circulate in the blood, resulting in a delayed response from the immune system. This delay may be sufficient for the delta variant in order to reproduce sufficiently in the body.

Researchers in Israel wanted to investigate how much and how quickly the vaccination protection actually wears off. For this purpose, the team around Ariel Israel from the Leumit health insurance company evaluated data from more than 80,000 vaccinated test subjects. The researchers compared how many of the participants were SARS-CoV-2 positive despite the vaccination and how this proportion progressed with increasing time after the vaccination.

Israel was among the first to launch a large-scale vaccination campaign“According to the researchers. With the help of the vaccine from BioNTech / Pfizer, broad immunization of the population in the country was achieved very early on. Accordingly, Israel was also one of the first countries to register a significant increase in the number of infections despite vaccination. So it is practically the ideal country to investigate the decreasing vaccination protection.

Vaccination protection begins to decrease after 3 months

The researchers concluded that vaccination protection remained stable for the first three months after the second vaccination dose. The proportion of corona infections among the test subjects was around 1.3 percent during this period. Some of the participants were tested routinely, so that among this 1.3 percent there were also numerous infections that were symptom-free. The researchers saw this as confirmation of the good effect of the mRNA vaccine.

After four months, however, the infection rates went up noticeably. The positive tests now made up a share of 2.4 percent – so they doubled. In the fifth month their share was 4.6 percent. In the sixth month, the infection rate rose again significantly, it was now 10.3 percent. After six months it was finally 15.5 percent.

Researchers recommend booster vaccinations

The results thus confirm that the vaccination protection against SARS-CoV-2 begins to decrease from the third month. After six months, the risk of infection for vaccinated people is already a good 15 percent. However, the study only looked at whether the participants were infected. How strong the Covid 19 symptoms were and whether the participants even had any was not asked.

Nevertheless, the researchers emphasize that their results show how useful a booster vaccination from the 5th month after the second vaccination dose can be in order to contain the further spread of the virus. Because even infected people who are not sick can pass the virus on. In addition to the proportion of unvaccinated people, this effect is one of the main drivers of the current fourth wave in Germany.


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