How long does the effect of Corona vaccination last?

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Vaccinations protect against covid-19. How long the effect lasts depends on many factors. Data show: For all vaccines, protection against a severe course of covid remains very high for a very long time.

How long does the protection of Corona vaccinations last? This is a question that concerns many people, but it is not easy to answer. On the one hand, the increasing number of vaccine breakthroughs – symptomatic Sars-CoV-2 infections despite complete vaccination – shows that the vaccines do not provide lasting protection against Covid-19. On the other hand, however, they reliably prevent severe disease progression, experts point out – and data show.

First, there is the question of what vaccine protection is in the first place. The registration studies for the vaccines primarily measured how well they protected against disease – that is, against an infection with symptoms such as cough, fever and cold. This value determines the reported vaccine effectiveness.

High protection against severe disease
“For the mRNA vaccines, this was 94 to 95 percent, for Astrazeneca’s vaccine 60 to 80 percent, depending on the vaccination interval, and for Johnson & Johnson 66 to 67 percent was found,” says Carsten Watzl, an immunologist at the Leibniz Institute for Occupational Research at the Technical University of Dortmund. “The protection against severe disease was even better, but could never be stated so precisely in the studies because, fortunately, at the time there were only a handful of severe cases,” emphasizes the secretary general of the German Society for Immunology.

Thanks to the ongoing vaccination campaign, the effectiveness can now also be read off from data beyond the approval studies – which means that more differentiated statements on vaccination protection are possible. For example, Leif Erik Sander, head of the Infection Immunology and Vaccine Research Group at Berlin’s Charité University Hospital, explains, “We find that protection against infection, even symptomatic infection, declines somewhat over time when you look at the population as a whole.” Some research suggested that a diminishing protective effect could be seen as early as seven to eight weeks after a full vaccination.

Vaccine protection wanes faster in older people
Data from the United Kingdom and Israel also show that vaccination protection fades more rapidly in older people. Furthermore, a British study, the results of which were published as a preprint, showed that the probability of falling ill despite vaccination increases with the length of time since immunization.

Supplementary figures were recently provided by a study conducted by the U.S. health authority CDC: According to this study, the effectiveness of the Biontech preparation dropped to 77 percent after four months, while Moderna remained almost stable with an effectiveness of 92 percent.

According to Watzl, the Robert Koch Institute’s (RKI) figures on vaccine breakthroughs match this: “Moderna has had the fewest breakthrough infections so far, Biontech and Astrazeneca are on par, although one would still have to take into account who received which vaccine – i.e. whether the young, healthy tended to receive Moderna and the elderly tended to receive Astrazeneca or Biontech.” The Johnson & Johnson vaccine is the worst performer, although only one dose has been given so far.

Protection against infection with symptoms is only one aspect of the question of duration of vaccine protection. Another is protection against severe illness, which can involve hospitalization, ventilation or even death. “This protection is almost as high with all vaccines after six months as it was at the beginning,” Sander emphasizes.

The RKI estimates the vaccine effectiveness of all licensed vaccines against Covid-19 in its new weekly report for calendar weeks 35 to 38: According to the report, protection against hospitalization is 93 percent in 18- to 59-year-olds and about 89 percent in the age group 60 and older.

Protection from treatment in the intensive care unit is 96 percent in the younger group and 94 percent in the older group, according to the report, and the institute puts protection from death in the two age groups at 97 and 88 percent, respectively.

“Protection against the serious disease remains intact – with the exception of the elderly and immunocompromised,” Sander emphasizes. “And that’s why these people are now being offered the third vaccination.” In Austria a recommendation that people with weakened immune systems should receive a booster vaccination.

Protection against the serious disease remains intact.
But why does vaccination protection weaken in the first place? Sander explains that its duration and strength are influenced by individual factors as well as the type of vaccination and pathogen: “Sars-CoV-2 is a very contagious pathogen that infects the respiratory tract, replicates there and can be passed on directly. That’s why it’s much more difficult to build up complete immune protection against it than against other pathogens, which first have to pass through the bloodstream.”

Watzl uses a comparison with an umbrella to illustrate the role played by the emergence of the delta variant: “Depending on how good the vaccine and my immune system were, the bigger or smaller the umbrella. If it rains normally, I stay dry. But if there’s a strong storm that also comes from the side, I get wet despite the umbrella.” The Delta variant, with its much higher viral load and high potential for contagion, represents such a storm, he said.

A fresh Corona vaccine every year?
Does that mean a new umbrella is needed every year, so similar to the flu virus, you need an annual vaccination? Sander doesn’t think so: “The flu virus is very variable and reassembles every year, so last year’s vaccine protection may not work. But that’s because of the virus.”

Coronaviruses are not capable of this: they do mutate and exchange individual building blocks, which can weaken the antibody response. A third vaccination would nevertheless build up long-lasting protection. In addition, everyone would come into contact with the pathogen sooner or later, which would again refresh the vaccine protection.

To what extent the currently observed breakthrough infections improve the immune response of those infected is still unclear, however, Sander said: “I assume that there will be a booster effect. But how good that is is still subject to research.”