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The VU researchers also recently conducted a study that showed that two weeks after the onset of symptoms or after a positive PCR test, most people already have antibodies in their blood. They were detected later, one or two months later.
“This is the dynamics of the immune response. Typically, the levels of antibodies in the blood increase over time, peak and then begin to decrease unless a person is repeatedly exposed to the same antigen. This is the case with any immune response, “says the professor. A. Žvirblienė.
Aurelija Žvirblienė
Recently, VU researchers in Nemenčinė studied people whose new coronavirus infection was confirmed 2 months ago. The vast majority of these people had specific antibodies to the virus, even if there were no symptoms of infection or they were very mild.
“Antibodies generally don’t drop that fast,” said immunologist A. Žvirblienė, adding that after 4 to 6 months, antibody levels may drop, and their starting levels may depend on the severity of the infection.
“If a person develops severe symptoms, the condition is severe, usually more antibodies are formed because a serious infection activates the immune system more,” said Professor VU. A. Žvirblienė.
“And if the form of the infection is asymptomatic or very mild, there may be fewer antibodies from the beginning of the disease.”
The researcher says that this is the normal course of the immune response. After the decrease in antibodies, so-called immune memory cells are formed, the activity of which cannot be measured, but these cells protect the human body from reinfection or other infection is easier.
“Those cells just wait for the antigen to reappear, then they quickly reactivate. A drop in antibody levels does not necessarily mean that the immune response has completely disappeared. Immunity is ensured not only by antibodies, but also by other components of the immune system: T lymphocytes, and their activity is difficult to measure, “says Professor. A. Žvirblienė emphasizes that it cannot be concluded that immunity disappears due to Complete 3 months after the onset of COVID-19 symptoms.
However, it is also difficult to say that if there are no antibodies, the person will still be resistant to the virus.
“Of course, it is very good if a person has virus neutralizing antibodies that can inactivate the virus very quickly. And if its level is so low that it can no longer be detected, it takes time for the immune system to react to the virus again, the professor said. A. Žvirblienė.
– But even if the antibodies are no longer detectable in the blood, we can have those cells in the immune memory. Still, we cannot know if we really have them and how many we have because it is impossible to measure them. If we have them, it is clear if the virus has entered the body again, but the person does not get sick. This means that the virus has been able to activate immune memory cells and provide that protection. Also, it happens much faster than when a person is exposed to the virus for the first time. “
Are the hopes of the vaccine really not dying yet? We asked the immunologist.
“No, there is no way. Various test vaccine formats are being developed. Of course, vaccine developers are trying to choose a format that activates the immune system in the most effective way possible,” Professor A. Žvirblienė said.
– Of course, the number of vaccines to be vaccinated will also be verified during vaccine development, once, twice, or perhaps three times.
If the vaccine was protected for less than 3 months, we couldn’t say that the vaccine was developed. “
The researcher says that for these reasons, the vaccine should not be expected to develop in a few months.
The professor says that if we want to know if the vaccine will work for at least a year after vaccination, we will have to measure various parameters of the immune system, not only measure the antibodies, but also neutralize the antibodies, which are much more difficult to measure.
“Then you must work with the virus itself and perform experiments to see how the serum of the immunized person can stop the virus from multiplying. These are much more complex experiments, said prof. A. Žvirblienė.
– Infection experiments, such as monkeys, should be carried out during the development of the vaccine. After administering the vaccine, the virus becomes infected and it is verified whether the immunized individual is protected. Then an important period of time will be clarified as to whether the individual is protected for 3 months, or a year, or two. That is the normal way of developing a vaccine: everything has to be studied very well, how long the protective response lasts and how long these levels of immunity remain. “
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