Researchers at the University of Bern have studied antibody levels against Sars-CoV-2 and their influence on infections with different variants of the virus in employees of the Bern Cantonal Police for over a year. Among other things, the results show that antibody levels offered different levels of protection depending on the variant of the virus and that police officers did not become infected with Covid-19 more frequently than the rest of the population, even though they have very frequent contact with people.
From 2021 to 2022, around 1,000 subjects from the Bern Cantonal Police (around 35% of all employees) took part in a Sars-CoV-2 antibody study conducted by the Institute for Infectious Diseases (IFIK) at the University of Bern. With the help of the Interregional Blood Donation SRC Bern, blood samples were taken from police officers throughout the canton. Over 16 months, the researchers investigated how the amount of antibodies in the blood develops and how this affects protection against infection with Covid-19.
The researchers led by Parham Sendi of the Institute of Infectious Diseases (IFIK) investigated which factors have an influence on the amount of antibodies. It is now known that this decreases over time and also with age. The team found that even in this relatively young and healthy population of cantonal police, there was an association between increasing age and decreasing antibody levels over time, regardless of whether the antibodies came from infection or vaccination. Furthermore, they were able to demonstrate a correlation between the amount of antibodies and protection against infection, i.e. the higher the amount of antibodies, the better the protection against infection. However, the results showed marked differences between the alpha and delta variants on the one hand and the omicron variant on the other. In addition, the study showed that police officers who were highly exposed during the pandemic were not more likely to become infected than the general population of comparable age. The study was published in the Journal of Medical Virology.
Study unique in Switzerland
To find out how the amount of antibodies - elicited either by infection with the virus or by vaccination or both - is associated with protection against SARS-CoV-2 infection, blood was drawn from the participants up to five times. This made it possible to analyze not only punctual intervals, but the dynamics of antibodies over the entire 16-month period - that is, from the alpha and delta waves to the omicron wave, in which booster vaccinations had already been given. At the same time, questionnaires and other tests were used to track the number of infections. Using the results from the blood samples, mathematical models were created to calculate probabilities of ’protection against infection’ based on the levels of antibodies. This allowed the direct correlation between antibody levels in the blood with protection against infection to be studied. This long-term study of the development of antibodies in a young and healthy but highly exposed population - which does not work in the healthcare sector - is unique in Switzerland,’ says study leader Parham Sendi. ’It is important to analyze such high-quality domestic data because not all factors from foreign research can be transferred uncritically for every country,’ he adds.
Different protection with virus variants
During the alpha and delta waves, about 90 percent of study participants received at least two doses of Covid-19 vaccine. The researchers found that during these periods, vaccination was effective against severe disease courses as well as mild and asymptomatic infections. ’Here, even so-called ’normal’ antibody levels were protective,’ Sendi explains. From December 21, 2021, the Omikron variant, which was more easily transmissible by mutation, dominated in Switzerland. Here, Covid 19 vaccination or a passed infection was shown to be effective against severe disease courses, but not against infections without symptoms or with mild symptoms. People who had already had an infection and a vaccination (so-called hybrid immunity) were least likely to be infected with the Omikron variant. According to the mathematical model, very high antibody levels were necessary to be protected against the Omikron variant. However, such high levels were found in only a very small fraction of the study participants, and even in these the levels decreased over time.
Important for possible future virus variants
’With respect to the Covid 19 vaccine, our study provides another piece of the puzzle in explaining why one could be infected with the Omikron variant despite booster vaccination. ’However, this does not mean that booster vaccination was useless, since, as numerous other studies have shown, it helped protect against severe, hospital-acquired disease, especially in vulnerable individuals,’ Sendi explains. ’Moreover, the results show that in healthy individuals, it is not necessary to determine antibodies for individual decision-making on whether or not to get vaccinated,’ Sendi adds. He recommends - in addition to individual consideration - following the indications of the Federal Commission on Immunization. Severe courses of the disease must be prevented, especially in people at risk.
The researchers see the results as confirming the importance of a comprehensive strategy to combat covid-19. During a pandemic or wave of infection, in addition to vaccination, it is central to continue to follow other protective measures such as wearing masks, maintaining distance rules and washing hands regularly. In addition, Sendi says it is important to push ahead with the development of new vaccines and therapies to be prepared for possible future variants of the virus.
