Study with Bern Cantonal Police provides new insights into antibodies and protection against COVID-19 infections

Over a period of more than a year, researchers at the University of Bern studied antibody levels against SARS-CoV-2 in employees of the Bern Cantonal Police and their influence on infections with different variants of the virus. Among other things, the results show that antibody levels offered different levels of protection depending on the virus variant, and that police officers did not become infected with COVID-19 more often than the rest of the population, even though they have very frequent contact with other people.

Read the original media release here. (in German)

From 2021 to 2022, around 1,000 participants 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) of the University of Bern. With the help of the Interregional Blood Transfusion SRC Bern, blood samples were taken from police officers throughout the canton. Over 16 months, the researchers studied how the amount of antibodies in the blood develops and how this affects protection against COVID-19 infections.

The researchers led by Prof. Dr Parham Sendi from the Institute for Infectious Diseases (IFIK) investigated which factors influence 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 the Cantonal Police, there is an association between increasing age and a decreasing amount of antibodies over time, regardless of whether the antibodies came from an infection or a vaccination. They were also able to demonstrate a correlation between the level 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. It also emerged that the police officers, who were highly exposed during the pandemic, did not become infected more often than the general population of a comparable age. The study was published in the Journal of Medical Virology.

A study unique in Switzerland #

To find out how the amount of antibodies – induced either by infection with the virus, by vaccination or by both – is linked to protection against SARS-CoV-2 infection, blood was taken from participants up to five times. This made it possible to analyse not just individual points in time but the dynamics of the antibodies over the entire period of 16 months – from the Alpha and Delta waves to the Omicron wave, when booster vaccinations were already available. At the same time, the number of infections was tracked using questionnaires and other tests. Based on the results of the blood samples, mathematical models were created to calculate probabilities of “protection against infection” based on the level of antibodies. This made it possible to investigate the direct link between the amount of antibodies in the blood and protection against infection. “This long-term study of antibody development in a young and healthy but highly exposed population – one that does not work in healthcare – is unique in Switzerland,” says study leader Parham Sendi. “It is important to analyse such high-quality domestic data, because not all factors from research abroad can be transferred uncritically to every country,” he adds.

Different protection against virus variants #

During the Alpha and Delta waves, around 90 per cent of study participants received at least two doses of a COVID-19 vaccine. The researchers found that during these periods, vaccination was effective against both severe disease and mild and asymptomatic infections. “Here, even so-called ‘normal’ antibody levels were protective,” explains Sendi. From 21 December 2021, the Omicron variant, which was more easily transmissible due to mutation, dominated in Switzerland. Here it became apparent that COVID-19 vaccination or a previous infection was effective against severe disease, but not against infections without symptoms or with mild symptoms. People who had already had both an infection and a vaccination (so-called hybrid immunity) had the lowest risk of infection with the Omicron variant. According to the mathematical model, very high antibody levels were necessary to be protected against the Omicron variant as well. However, such high levels were found in only a very small fraction of study participants, and even in these the levels declined over time.

Important for any future virus variants #

“With regard to COVID-19 vaccination, our study provides another piece of the puzzle in explaining why people could become infected with the Omicron variant despite a booster vaccination. However, this does not mean that the booster vaccination was useless, as – as numerous other studies have shown – it helped to protect against severe disease requiring hospitalisation, especially in vulnerable people,” explains Sendi. “In addition, the results show that in healthy people it is not necessary to measure antibodies in order to make an individual decision on whether or not to get vaccinated,” Sendi adds. In addition to weighing up individual circumstances, he recommends following the guidance of the Federal Commission for Vaccination Issues. Severe disease must be prevented, especially in vulnerable people.

The researchers see the results as confirming the importance of a comprehensive strategy for combating COVID-19. During a pandemic or wave of infection, it is essential, in addition to vaccination, to continue to follow other protective measures such as wearing masks, keeping a distance and washing hands regularly. Furthermore, according to Sendi, it is important to advance the development of new vaccines and therapies in order to be prepared for possible future variants of the virus.