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Despite triple vaccination, many people are currently infected with omicron. Official data show that they are well protected against severe infections. Experts hope that the breakthrough infections could act as a booster for boostered people and help contain the pandemic in the long term. Some questions about that remain, however.
Cold symptoms, headache, aching limbs, fever in some cases – even triple-vaccinated people are not immune to a noticeable omicron infection. There are two reasons why more breakthrough infections are being recorded at the moment. First is the high incidence of infection. “With high incidence, also more breakthrough infections – because a lot of viruses circulates,” virologist Monika Redlberger-Fritz of MedUni Vienna told ORF.at.
The second reason lies in the properties of the virus and the immune response of humans. Omicron can bypass the antibody response – the immune system’s first line of defense – more efficiently than previous virus variants. In addition, according to Redlberger-Fritz, only a limited number of the antibodies formed after vaccination are present on the mucous membranes in the nasopharynx, the entry point for the virus.
Omicron: “Milder” courses with limitation
When – as in the case of Omikron – “you are faced with exorbitantly high viral loads, it is a problem of numbers,” the virologist says. So it happens that viruses dock, attack a host cell, and cause infection in the upper respiratory tract.
Because the majority of antibodies are circulating in the blood, vaccination prevents “the virus from spreading deep down and causing severe pneumonia,” Redlberger-Fritz says, “that’s why vaccinated people have the advantage of being protected from severe infections.”
The unvaccinated enjoy no such protection. While there is always talk of “milder” omicron infection, the critical question is “milder” relative to what? “These supposedly milder courses are milder only compared to the delta variant. In terms of severity of disease, we’re on the order of alpha in unvaccinated people,” says the physician, who is a member of the National Immunization Panel (NIG).
Three spike contacts for good immune response
With omicron spreading worldwide, another type of protection against SARS-CoV-2 is coming into focus: hybrid immunity. It occurs in people who are both vaccinated and recovered. According to a recent research paper from Germany, the immune system must have been exposed to the spike protein three times to mount a high-quality immune response – even against the omicron variant.
Quality and quantity
Protzer also referred to mutatis mutandis as the relationship between quality and quantity on Twitter, saying her work showed that the immune system needs time “to form high-quality antibodies that show strong binding.” This strong binding is at least as necessary as high antibody counts. In other words, a high antibody titer, she said.
Therefore, of great importance is the interval between vaccinations, according to Redlberger-Fritz. “If you boost too early, it does relatively little for the immune system,” says the virologist. That’s because the antibodies need time to mature. According to the National Vaccination Committee, there should be at least four months between the second and third vaccination.
Antibodies disappear, memory cells remain
Numerous studies have shown that the number of antibodies decreases significantly over time, both after recovery and after triple vaccination. In contrast, the response of memory cells is more consistent. They are formed after immunization or infection, recognize the pathogen again, and set defense mechanisms in motion, such as developing antibodies. The process takes several hours. Therefore, even these cells cannot prevent infection. They can prevent the spread of viruses in the body. A severe course of the disease can usually be controlled.
According to some studies, the combination of vaccination and infections is likely to cause long-lived memory B cells to produce higher-quality antibodies that also respond to different variants. In vaccinated and recovered people, the immune response to omicron was more substantial than in those who were vaccinated only. This was shown in a recent peer-reviewed study published by the Medical University of Innsbruck.
In turn, breakthrough infection with Omicron is also likely to protect against other variants. “Those who are vaccinated and Omicron-infected not only have antibodies against all known variants, but also very high levels of them,” virologist Dorothee von Laer, who was involved in the Innsbruck study, told the daily newspaper Kurier.
In contrast, unvaccinated people who gassed after an omicron infection “would not have excellent antibody levels, and the antibodies that we could detect could also only inactivate omicron, neutralize it, and not other variants,” von Laer added. According to simulation researcher Niki Popper, the level of immunization against Omikron in the population was just over 67 percent in Austria as of Feb. 1. According to the model calculation, sixteen percent of those are recovered people who are not immunized.
Reinfection with Omicron not excluded
It isn’t easy to assess the impact of the omicron subtype BA.2, which is on the rise in Austria. For those recovering from omicron without vaccination, reinfection with omicron is “something to be reckoned with,” the virologist told Kurier newspaper.”In general, BA.1 and BA.2 are closely related, and probably in vaccinated people antibodies against BA.1 also protect against BA.2, but there is no definitive answer to that yet.”
Is the pandemic now over for triple-vaccinated people with breakthrough infection? That cannot be predicted. Virologist Redlberger-Fritz told ORF.at: “It would be unethical to say: If you have now gone through the infection, you are immune for next year. You can only try to prevent the severe courses through vaccination – and that has worked very well so far.”
– source: orf.at/picture: pixabay.com
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