Booster vaccination increases protection against the micron. But why does it decrease over time? Will we have to receive reinforcements every three months? Check answers to the most frequently asked questions about the booster. How does booster vaccination work against the omicron? After basic immunization – that is, two doses or, in the case of Janssen’s vaccine, one – protection against infection by the omicron variant of the coronavirus wanes very quickly, explains Sebastian Ulbert, a vaccine specialist at the Fraunhofer Institute for Cell Therapy and Immunology, from Germany. Booster significantly improves this protection, at least the first time after conventional vaccination, because more antibodies are produced. According to virologist Christian Drosten, from the Charité Hospital in Berlin, data from a Danish study show that the third dose greatly reduced the risk of infection by the omicron and made a difference in the current control of the spread. On the other hand, basic immunization is still very important to protect against severe cases, says Ulbert. Immunologist Carsten Watzl draws attention to a report by the British health authority UKHSA on the effectiveness of vaccination against a severe course with the omicron, which leads to hospitalization. According to the study, protection up to six months after the second dose is around 72%. After the boost, however, it goes up to about 88%. How long does the protection last after the booster? It’s not yet possible to say with certainty how long the protection will last in each case, given the recent wave of the omicron variant, says Ulbert. Booster vaccination expands the protective effect at least considerably and evokes an enhanced immune response. Why does booster protection decrease over time? Even after the booster vaccination, protection against infections will decrease over time. “The many antibodies you have after the booster are lost again over time. The reason for this is that the immune system reacts to vaccination like it reacts to an infection and, first of all, it produces a lot of antibodies,” explains Watzl. At some point, however, these antibodies would no longer be needed, so the number would be significantly reduced. This increases the risk of getting infected again. Is the booster necessary? According to Watzl, vaccine protection is still necessary because the most important objective is to contain the spread of the coronavirus, as not everyone is adequately protected against serious events. Looking ahead, however, the main objective is to protect against severe cases of the disease – and this is decreasing much more slowly. Regular reinforcements can be helpful for at-risk groups. In the case of younger, healthier people, however, it is conceivable in the future that regular booster vaccinations will no longer be necessary as long as the virus does not change significantly. Israel is already applying the fourth dose to some groups. According to data, the second booster raised antibodies again. It was “good, but not enough,” said Gili Regev, head of the study. Right after the fourth dose, the body returned to the same level of antibodies as right after the third — and it’s not the goal to vaccinate everyone against the coronavirus every four months. For risk groups such as the elderly, the fourth dose is the right way to go for now – for the rest of the population it is questionable. Why does vaccination protect less against the micron than other variants? Vaccines appear to protect less against the micron than against other variants, such as delta. This is suggested by the growing record of people with basic vaccinations, or even boosters, who contract the variant. “Vaccines were developed based on a specific sequence of the spike protein that is on the surface of the virus. However, there are variants that have altered the spike protein at crucial points”, explains vaccine specialist Ulbert. As a result, this variant of the virus is no longer as well recognized by the immune system. Also, with more contagious variants, fewer viruses are usually needed for an infection. How does the vaccine generally protect against the micron? When it comes to vaccination effectiveness, a distinction must be made between protection against infection and protection against severe cases of the disease, says Watzl. “Pure protection against infection with the omicron will always be suboptimal with current vaccines,” he said. But he points out that “vaccines still do what they’re supposed to: protect against serious strokes, and we’re currently seeing that with the micron.” An analysis recently presented by the UK health authority UKHSA indicates that booster vaccination of the elderly also offers a high level of protection against severe cases of the omicron. Three months after the third dose, protection against hospitalization for people aged 65 and over is about 90%. Against coronavirus infection with mild symptoms, it is 30%, indicate preliminary studies. le (dpa, ots) 
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