After the outbreak in Nemenčinė, coronavirus-infected antibodies were tested 3 times: their changes

The outbreak provided valuable knowledge about the coronavirus to researchers at the Vilnius University Life Sciences Center. After examining the antibodies against coronavirus outbreaks at the company where the coronavirus outbreak was recorded three times, they were able to monitor the maintenance of naturally acquired immunity over time.

“It is a case in which the exact beginning of an outbreak is known, when people are exactly infected. So it was very interesting for us to gather and study such a cohort, how the antibodies were formed, how long they last.

We conducted the study three times: two months later, six months later and almost 13 months after the outbreak, ”said Professor Aurelija Žvirblienė, Head of the Department of Immunology and Cell Biology at the Vilnius University Life Sciences Center (VU ), who directed the study to Delfi., clarifying that all the people participated in the study voluntarily and that a bioethical permit had been obtained.

After the first stage, most had antibodies.

The study was conducted for the first time two months after the outbreak, in June 2020. The Nemenčinė company, which has attracted the attention of scientists, employs about 300 people. In April 2020, when the coronavirus spread here, the infection infected around a third of its workers.

“All the employees of the company have undergone a PCR test several times. Therefore, it is known exactly how many of them were infected. Later, even the entire city of Nemenčinė was tested for the virus,” recalled the professor. .

During the first phase, VU researchers examined about 50 company employees infected with coronavirus. The subjects were of working age, between approximately 20 and approximately 62 years. Due to the particularities of the company, the majority of those surveyed were women. Those who were diagnosed with coronavirus were studied, regardless of whether the infection was asymptomatic, if they had very mild symptoms or if the people were more or less ill, which even required hospital treatment.

“At the beginning of the study, in June 2020, it was still not very clear if the coronavirus elicited any immune responses or if antibodies were formed. We also did not yet know whether antibodies formed in those who had relapsed an asymptomatic infection. There were many unclear questions, ”recalls A. Žvirblienė.

In the first study, researchers set the goal of looking at overall antibody levels in those who were diagnosed with an asymptomatic infection. It was not yet possible to measure the antibody titer at that time. The researchers used only rapid tests because they did not have quantitative tests.

The study showed that antibodies were formed in the majority (92 percent) of people who were asymptomatic or nearly asymptomatic. The latter named some symptom, such as a heaviness in the head, a rise in temperature to 37.1 degrees, just because they were aware of the coronavirus that they were diagnosed with.

Of all the people studied, asymptomatic or almost asymptomatic, about 20 percent.

The severity of the disease was not necessarily determined by age.

Within the company, PCR testing has been carried out continuously since the coronavirus outbreak. These data also provided researchers with information on how often people have asymptomatic or only very mild coronavirus symptoms.

“At that time, in the summer of 2020, some experts said that asymptomatically, the disease affects almost 90 percent. Our research has shown that it really is not. About half of people get sick with a lot of easily or asymptomatically, “said the researcher.

The researchers who studied the employees of the Nemenčinė company also pointed out that the severity of the disease does not necessarily depend on the age of the infected person.

“There were older people who only had mild symptoms, and there were younger people, 40 to 50 years old, who were seriously ill and were hospitalized.

There were also young people who got sick very easily but they infected their families. We did not study family members, but people voluntarily agreed to tell us. From these stories, we learned that some, having become ill very easily, transmitted the virus to their older relatives, eg. Eg parents, and they were very sick, they were in the hospital, even in intensive care units, ”said A. Žvirblienė.

For the second time, the study wanted to double double

Although it appeared that the Nemenčinė employee survey conducted in June 2020 would be only one time, the researchers decided to see how the situation changed in six months. Thus, in October 2020, with the start of the second wave of coronavirus, VU researchers examined employees of the same company for the second time.

“After 6 months, 100 people came who wanted to participate in the study. Not all were infected with coronavirus. Of those who did not get sick, of course, we did not find any offspring. Of the 100 who came to be examined six months later, around than 60 had fallen ill in the spring.

Of those who participated in our first study and had antibodies, half a year later all still had antibodies, ”said the professor.

Antibody titers were already measured in the second study.

“It just came to our knowledge then. The antibody levels didn’t get close to the limit. But we couldn’t tell if it decreased or increased. We could only establish the fact that people still had antibodies after 6 months, regardless of whether they were asymptomatic or more serious ”, explained A. Žvirblienė.

The antibodies persisted even after a year.

The researchers decided to repeat the study after more than a year, as data on the long-term survival of antibodies after exposure to the coronavirus is still scarce. Thus, in May 2021, 13 months after the outbreak, they began again to investigate the employees of the Nemenčinė company.

For the third time, nearly 100 people attended the study. But because the coronavirus vaccine was already available and the company was quite active in encouraging its employees to get vaccinated, a significant proportion of the subjects who had fallen ill in April 2020 had also been vaccinated.

There were nearly 50 unvaccinated and relapsing people, enough for the researchers to assess how the antibodies persisted after 13 months.

“The vast majority, more than 80%, of people who had not been vaccinated but had been ill had antibodies for 13 months. In half a year, the level of antibodies in most of them has decreased, but for some people even it has increased, “said the interviewee.

When asked if this meant that these people were re-infected, A. Žvirblienė said that the company constantly tests its employees with PCR tests after the outbreak. Only one case of reinfection was detected in the test, and this person did not even show any symptoms when he was infected a second time with coronavirus.

“Although the PCR tests did not show reinfection in everyone else, the increase in antibody levels may indicate that they were exposed to the virus, they simply did not feel any symptoms and may not have released the virus into the environment,” said the scientific. , who added that for the coronavirus, antibody levels were very high.

A. Žvirblienė said the company is also being consulted about a possible extension of the investigation in October this year, when a year and a half will have passed since the outbreak. It is true that it is possible that at that time most of the people infected at that time are already vaccinated.

If they remain unvaccinated, the researchers will be interested to see if the antibodies persist after a year and a half of infection after being vaccinated, and if the naturally acquired immunity to the coronavirus would be resistant to the delta strain currently circulating.