Researchers at the University of Bern spent over a year analysing antibody levels against Sars-CoV-2 in employees of the Bern Cantonal Police and their influence on infection with different variants of the virus. Among other things, the results show that the antibody levels offered different levels of protection depending on the virus variant and that police officers were not infected with Covid-19 more frequently than the rest of the population, even though they have very frequent contact with people.
Read the original press release here.
From 2021 to 2022, around 1,000 test subjects from the Bern Cantonal Police (around 35% of all employees) took part in a Sars-CoV-2 antibody study conducted by the Institute of Infectious Diseases (IFIK) at the University of Bern. With the help of the Interregional Blood Donor SRC Bern, blood samples were taken from police officers throughout the canton. Over a period of 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 Prof Dr Parham Sendi from 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 is an association between increasing age and decreasing antibody levels over time, regardless of whether the antibodies originated 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 level 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 showed that police officers who were heavily exposed during the pandemic did not become infected more frequently than the general population of a comparable age. The study was conducted in Journal of Medical Virology published.
In order to find out how the amount of antibodies - caused either by infection with the virus or by vaccination or both - is associated with protection against SARS-CoV-2 infection, blood was taken from the participants up to five times. This made it possible to analyse not only selective intervals, but also the dynamics of the antibodies over the entire 16-month period - i.e. from the alpha and delta waves to the omicron wave, in which there were already booster vaccinations. At the same time, the number of infections was tracked using questionnaires and other tests. Using the results from the blood samples, mathematical models were created to calculate probabilities of "protection against infection" based on the level of antibody levels. This made it possible to analyse the direct correlation between the amount of antibodies in the blood and protection against infection. "This long-term study of the development of antibodies in a young and healthy but highly exposed population - who do not work in the healthcare sector - is unique in Switzerland," says Parham Sendi, who led the study. "It is important to analyse such high-quality domestic data because not all factors from foreign research can be transferred uncritically to every country," he adds.
During the alpha and delta waves, around 90 per cent of the study participants received at least two doses of a Covid-19 vaccination. The researchers found that the vaccination was effective against both severe courses of the disease and mild and asymptomatic infections during these periods. "Even so-called 'normal' antibody levels were protective here," explains Sendi. From 21 December 2021, the Omikron variant, which was easier to transmit due to mutation, dominated in Switzerland. This showed that the Covid-19 vaccination or a past infection were effective against severe courses of the disease, but not against infections without symptoms or with mild symptoms. The risk of infection with the Omikron variant was lowest in people who had already had an infection and a vaccination (so-called hybrid immunity). According to the mathematical model, very high antibody levels were necessary to be protected against the Omikron variant. However, such high values were only found in a very small fraction of the study participants, and even in these the values fell over the course of the study.
"With regard to the Covid-19 vaccination, our study provides another piece of the puzzle in explaining why people could be infected with the Omikron variant despite a booster vaccination. However, this does not mean that the booster vaccination was useless, since - as numerous other studies have shown - it helped to protect against severe hospitalisation, especially in people at risk," explains Sendi. "In addition, the results show that it is not necessary to determine antibodies in healthy individuals in order to make an individual decision on whether or not to be vaccinated," adds Sendi. In addition to individual judgement, he recommends adhering to the information provided by the Federal Commission on Vaccination. Severe courses of the disease must be prevented, especially in people at risk.
The researchers believe the results confirm the importance of a comprehensive strategy to combat Covid-19. During a pandemic or wave of infection, in addition to vaccination, it is crucial to continue to follow other protective measures such as wearing masks, social distancing and regular hand washing. According to Sendi, it is also important to press ahead with the development of new vaccines and therapies in order to be prepared for possible future variants of the virus.
Publication:
Parham Sendi, Nadja Widmer, Mattia Branca, Marc Thierstein, Annina Elisabeth Büchi, Dominik Güntensperger, Manuel Raphael Blum, Rossella Baldan, Caroline Tinguely, Dik Heg, Elitza S. Theel, Elie Berbari, Aaron J. Tande, Andrea Endimiani, Peter Gowland, Christoph Niederhauser, for the PoliCOV-19 study: Do quantitative levels of antispike-IgG antibodies aid in predicting protection from SARS-CoV-2 infection? Results from a longitudinal study in a police cohort, Journal of Medical Virology, 30 June 2023, https://doi.org/10.1002/jmv.28904
Institute for Infectious Diseases (IFIK)
The Institute of Infectious Diseases (IFIK) is part of the Medical Faculty of the University of Bern and combines diagnostic services, teaching and research in the fields of virology, bacteriology, mycology, parasitology and immunological infection analysis. The IFIK is also home to the Biosafety Centre, which supports research into highly pathogenic microorganisms. The research of the Experimental Virology group at the IFIK focuses on investigating how emerging respiratory pathogens, including influenza viruses and coronaviruses, are transmitted from animals to humans.
24.07.2023