With the number of infections in Switzerland on the increase again, it raises the question of the consequences of reinfection. A recently published preprint from the USA is currently ringing alarm bells. It shows that the risk of long-term consequences after a COVID-19 infection increases with the number of infections. The risks of hospitalization and mortality were also higher than in the control group. Vaccination status did not play a role. However, it is important in this respect to classify the results.
Today, after all the Delta and Omicron infections, and considering the booster vaccinations, the situation is presumably different.
Data only until September 2021
The study utilizes data from the national healthcare databases of the US Department of Veterans Affairs. With more than 5 million individuals, including just over 250’000 with a Covid infection and nearly 40’000 with a reinfection, the study can draw on a very large amount of data. Nevertheless, this is routine data and not patient-reported outcomes. It is therefore difficult to verify the quality of the data.
Furthermore, the situation today, following all the Delta and Omicron infections and the booster vaccinations, is probably different. This is because the data in the preprint only maps developments up to September 2021 and is most likely outdated by now. Currently, we do not yet know whether new infections will have serious long-term consequences.
80% of respondents reported worsening of Long COVID symptoms.
Trend: exacerbation of Long COVID by reinfection.
Among people who are already suffering from Long COVID, an aggravation of the situation tends to be observed. This is based on a survey conducted by Long COVID Kids among Long COVID sufferers in 30 countries between April 4, 2022 and June 19, 2022. It includes responses from 484 adults and 112 children who had experienced at least two Covid infections. The results were similar in adults and younger individuals. However, it should be noted that this is a relatively small data set, which is based on self-assessments.
Long-term consequences occurred in 89% of respondents after the first infection, in 10% after the second infection, and in 1% after the third infection. Most individuals who still had Long COVID symptoms at the time of reinfection reported that these had worsened. Seen in relative terms, 80% had worsening symptoms. 10% of individuals reported that their symptoms improved, however. Of those in whom Long COVID had subsided, 60% reported a recurrence of symptoms after reinfection. According to the researchers, this is one of the first studies to be published on the effects of reinfection on Long COVID, and their findings indicate that further investigation is needed.
Whether booster vaccination makes sense for Long COVID sufferers should be evaluated on an individual basis.
A combination of vaccination and infection provides the best protection
In the context of reinfection, the question also arises as to the role of immunity and the extent to which antibodies of previous variants, vaccination, or the combination of these (hybrid immunity) provide protection. The Swiss research program Corona Immunitas is investigating this area. In the sixth test phase of the project, a total of 2,553 participants was examined, including 739 from Ticino, 850 from Vaud and 964 from Zurich. In general, very high immunity is evident in all regions of Switzerland. According to the study, immunity was 97% across all age groups in June/July 2022. At least 51% of participants have developed so-called hybrid immunity. This means that they have been infected with Covid at least once, as well as receiving vaccination. As things stand today , it is believed that these individuals are best protected from severe disease. It is also observed that antibodies provide protection whatever the variant, meaning so-called cross-immunity.
Vaccination recommendations should be considered individually
These results show that the pandemic has become endemic. It is still important to continue protecting oneself with individual measures, however. Vaccination is still recommended for particularly vulnerable people. This is mainly because the (booster) vaccination reduces severe cases, as well as Long COVID . Whether a vaccination is useful if Long COVID already exists cannot be answered in a general way. In such cases, individual vaccination history, natural infection history, and the risk of experiencing a severe case must be taken into account. This is best discussed with a specialist (family doctor, epidemiologist, immunologist or specialized internist).
