The omicron variants BA.1 and BA.2, which dominated the infection process in Germany from December to April, can undermine protection against a Sars-CoV-2 infection after only three months, which vaccinations or a recovered infection can offer. This is the result of a study led by the University Hospital Frankfurt and the Goethe University.
In a study, a research team led by Marek Widera and Sandra Ciesek investigated how long antibodies, which the immune system produces for protection after a vaccination or after an infection, can neutralize the virus variants BA.1 and BA.2. The scientists collected blood samples from people who had been vaccinated twice or three times. They brought the blood serum, which contains antibodies, together with Sars-CoV-2 viruses and observed how many cells were infected.
The result: Six months after the second vaccination, the tested sera had practically no neutralizing effect on the omicron subtypes BA.1 and BA.2. Shortly after the booster vaccination, the protective effect was still very high, three months later the Piks offered hardly any protection: the majority of the sera tested were no longer able to neutralize the two virus variants.
The Robert Koch Institute (RKI), which examines the effectiveness of vaccinations in the “Living Systematic Review”, paints a similar picture of the effectiveness of vaccines before Omikron. A basic immunization against an asymptomatic or mild corona disease through the omicron variant offers only little protection and the effectiveness decreases significantly over time. “Even after booster vaccination, initial data suggest that protection against (symptomatic) infection will decrease over time,” says the RKI. Vaccination still offers good protection against serious illnesses.
Data from South Africa published in February shows that the vaccines have a good protective effect against omicrons with regard to hospital treatment: a double vaccination protects 70 percent against hospitalization. Another study shows that protection after a booster vaccination against severe courses lasted over seven months.
There are several reasons why the Omicron variants are able to bypass the immune protection after such a short time. The Frankfurt researcher Marek Widera explains the study results: “The fact that BA.1 and BA.2 can bypass the immune protection after only three months is due to the fact that the antibody titer in the serum – the amount of antibodies, so to speak – after a vaccination or infection in the course as time decreases.”
This is not only the case in the blood sera of the study. The number of antibodies in our bodies also decreases over time after an infection or vaccination. The immune system switches to energy-saving mode, so to speak. Instead of constantly forming a huge number of antibodies, the defense relies on special antibodies (B cells) that are trained to recognize the virus again. In this way, they can react at lightning speed if they come into contact with the virus again. The body’s own immune system does not only depend on the number of antibodies. The T-cells, for example, are also important.
But the new Omicron variants are getting better and better at committing immune escape. So you can bypass the body’s defenses. The reason: the antibodies cannot recognize the corona virus so well. Because: The omicron subvariants BA.1 and BA.2 differ in the genetic blueprint of the spike protein from each other and from other variants of the coronavirus. The spike protein is the part of the virus that it uses to dock onto human cells. In short, the omicron viruses BA.1 and BA.2 look different from the original variant of the coronavirus on which the vaccines are based and also differ from the original omicron variant.
The research team in Frankfurt also examined the effectiveness of three antibody preparations against Omikron BA.1 and BA.2. Such agents can be given preventively to people with a weakened immune system. This is done because, in some cases, people with immunodeficiency do not produce enough antibodies after being vaccinated. Virologist Sandra Ciesek explains: “We examined three such monoclonal antibodies in the laboratory and saw that their effectiveness depends very much on the virus variant. In order for us to be able to protect vulnerable patients with such preparations, it is therefore urgently necessary to also protect the patient test to what extent such antibodies can neutralize currently widespread virus variants.”
In Germany, the omicron subtypes BA.1 and BA.2 are no longer dominant, but the study results underline that “we must not relax in adapting our protective measures to the genetic changes of the Sars-CoV-2 virus, currently on the omicron variants BA.4 and BA.5,” says the virologist.
Sources: University Hospital Frankfurt study, study notification, South Africa study, RKI, Living Systematic Review, Medrxiv study