The Corona Immunitas project has published the results of the first large-scale epidemiological study carried out since the Omicron variant supplanted Delta in Switzerland in early 2022. The results indicate a significant amount of antibodies present and exceptionally high neutralisation levels. The study also confirms that hybrid immunity, a combination of vaccination and infection, is the most effective. Furthermore, this study validates the vaccination plans implemented by many countries, which focus on safeguarding vulnerable individuals.
The Corona Immunitas Ticino project is a joint effort between the Institute of Public Health at UniversitÓ della Svizzera italiana, the Department of Business Administration, Health and Social Affairs at SUPSI, EOC, and other local partners. This initiative is a part of the wider Corona Immunitas research programme promoted by the Swiss School of Public Health (SSPH+). The project began in 2020 with the aim of evaluating the prevalence of the SARS-CoV-2 virus and the growth of immunity in the community. The study, led by, among others, Dr Rebecca Amati, research assistant Anna Maria Annoni and Professor Emiliano Albanese of USI Faculty of Biomedical Sciences, was published in the International Journal of Epidemiology and compared the presence and levels of antibodies in the cantons of Ticino and Zurich in March and June/July 2022, then compared the results with data from the canton of Vaud.
As mentioned above, at least 51% of the participants developed hybrid immunity produced by the combination of vaccine and infection; of these, more than 96% had neutralising antibodies against the original strain, Delta, and Omicron variants. However, those who only received the vaccine and were not infected had lower levels of neutralising antibodies, especially against the Omicron variant. People who had not been vaccinated but had immunity from infection had much lower antibody levels, and less than half had neutralising antibodies.
Professor Albanese, the WHO has decreed the end of the health emergency. Why is it important to continue monitoring Covid immunity among the population?
It is important to keep track of the immune response to SARS-CoV-2 in the general population for various reasons. This will help determine the duration and effectiveness of different types of immune responses, particularly the hybrid response, which provides the most protection.
A second reason is to study the mediumand long-term effects of SARS-CoV-2 infection. Although there are numerous clinical studies on this topic, there are still limited epidemiological studies that analyse the general population. We are not aware of the number of people who suffer from mood disorders, such as depression and anxiety, or memory problems due to the virus and whether there is any correlation to the severity of COVID-19 symptoms. These answers are crucial for public health, as more people are infected than those who have been diagnosed with COVID-19.
Can these data be useful in view of new waves or future pandemics?
Absolutely. An example of this would be vaccination campaigns and their correlation with other measures to control future pandemics. Our research is among the first to establish that the strength of the immune response, precisely the neutralising capacity of antibodies, is diminished in newer strains of the virus. However, immunity is most effective when it combines vaccination and prior infection within an individual.
Is this superiority of hybrid immunity an outcome you expected?
To some degree, the outcome was predictable, as we had noticed similar findings during the Corona Immunitas research conducted last year. Dr Amati’s study, published in Eurosurveillance in 2022, has now been substantiated through a more extensive and diverse sample size and a more thorough evaluation of the antibodies’ neutralising capabilities over a more extended period.
Based on these data, can we say that Covid is now an endemic and no longer an epidemic disease?
COVID-19 is now considered an endemic disease, but our understanding of it remains limited.
An endemic disease is one that is consistently present in a particular geographic area or population group. These diseases are often viewed as ’normal’ because they tend to have a relatively stable or predictable pattern over time.
It’s worth mentioning that even if a disease is considered ’normal’, it can still have a significant impact on the health of those affected by it. Therefore, it’s crucial to implement appropriate surveillance, prevention, and control measures to manage endemic diseases and lessen their impact on public health.
Is the current vaccination strategy, which prioritises older people and immunocompromised, in line with the findings of this study?
Yes. Our data support the current vaccination strategy that focuses on sub-groups of the population at higher risk. As mentioned, vaccination confers a functional solid immunity. That is a lower probability of a severe course of the disease in case of re-infection.