Three years of Corona: what we have learned from the pandemic

This year, the WHO is announcing the end of the corona pandemic. The World Health Organization announced this in January. Not because there are almost no infections anymore – but because they don’t cause that much damage anymore.

This is also reflected in the excess mortality statistics: for the first time since June 2021, fewer people over the age of 65 are dying than expected. However, caution is advised when it comes to excess mortality statistics, as the Federal Bureau of Statistics (BFS) has included the past year as a completely normal year in the statistics. So even though the pandemic was not over and several experts also complained that the excess mortality in 2022 was still mainly due to the virus. 2020 and 2021 are not included in these statistics as exceptional pandemic years.

This decision has pushed up the expected number of deaths for this year. But mortality among the over-65s is now average compared to the years before Corona: 1200 deaths occurred in the first week of February – that was also the expected number at the beginning of February 2020.

There has been much debate about where Switzerland acted correctly, where it was too hesitant or where its measures were excessive. After three years of the pandemic, we've experienced - and learned - the epidemiology firsthand. The most important insights.

Do you remember? R0 is the basic reproduction number, which indicates how many other people an infected person infects on average if there are no immunities yet. This value seemed to have risen sharply over the three years of the pandemic, even rising above 10 with Omicron. But here too you should only settle after the pandemic: a study published in October 2022 by “Nature” and comparing the number of infections with the excess mortality showed a basic reproduction number of almost 2. This raises the risk of infection from Sars-CoV-2 in the flu range (R0 measles: 15). For the individual risk, however, it is just as relevant how many sick people are on the road - sometimes there were extremely many.

The Federal Council has long realized that the population can wear hygiene masks correctly. Properly worn FFP2 masks reduce the risk of infection for 20 minutes by a factor of a thousand, according to a calculation by the Max Planck Institute in Germany. An incorrectly worn copy with a factor of 25. And a hygiene mask with a factor of 13.

Masks and other social distancing measures have been so effective during the pandemic that other viruses have barely spread. As a result, the population's protection against flu and RS viruses has decreased slightly, which led to a violent wave of illness at the end of 2022. This became problematic for children's hospitals, because the three-year-old small children who had never been infected with it now had to go to the children's hospitals en masse.

There is still disagreement in research about exactly how many deaths have been prevented by the lockdowns. Usually it is not possible to estimate how many people would have been voluntarily separated in light of the new virus. As far back as 2020, David Nabarro, WHO Special Envoy against Covid-19, said: "It is a very extreme intervention in our living together and should only be the very last resort." In the spring of 2020, however, it was the first means of containing the pandemic, because there were not enough masks for everyone and there was still no vaccination. Governments tried to buy time until more was known about the virus – and the hoped-for vaccine was available. In retrospect, most are probably glad they only got infected after being vaccinated at least twice.

Schools across the country were closed for two months in the spring of 2020. This has never happened before. Even during World War II or the time of the Spanish flu, there were only regional closures of two to four weeks in Europe. In all OECD countries, schools were closed for an average of 78 working days in the first two years of the pandemic, i.e. almost four months. Only in Sweden and Japan have schools never been closed. It soon became clear that especially the younger students and students with a difficult family background suffered. And the learning progress checks also confirmed this in Switzerland.

A statistical model by biostatistician Leonhard Held as part of a work for the Swiss National Science Foundation eventually rejected this measure: There would be a 20 percent increase in infections among young people under the age of 15 in the spring if all other measures had remained at the same time. But about the same number of elderly people would have been infected, ie those who absolutely wanted to protect.

As islands, Australia, New Zealand and Japan had ideal conditions to keep the virus away: in Australia, the first major wave did not occur until late 2021. New Zealand only entered the pandemic with the advent of omicron. Japan even managed to flatten the curve until the summer of 2022. Most of the inhabitants of these countries were vaccinated and there was already a lot of knowledge about the virus, resulting in fewer deaths. China's second wave of violence hit a less immunized population with lockdown measures last December. China reported nearly 60,000 deaths between December 8, 2022 and January 12, 2023 — international experts came to much higher estimates.

Since PCR tests became taxable at the beginning of this year, the number of tests has fallen sharply. However, the pandemic is being monitored in 50 sewage treatment plants. An earlier low was reached in Zurich at the end of January and the number of viruses measured has now reached half of the December peak.

But is it still possible to know which variants are in circulation with so few PCR tests? Tanja Stadler, head of the CoV spectrum project at ETH, says that with a few hundred samples (instead of a thousand) you can get a global overview. However, the appearance of new variants is observed with a delay.

She thinks: “Now you no longer need thousands of sequences per month. However, it would be important to have a representative selection, such as all samples from medical practices' Sentinella reporting system along with samples from the hospitals and samples from returning travelers.” Positive corona samples from six hospitals in the cantons of Geneva, Lausanne, Zurich, Basel, Bern and the canton of Ticino are currently being sequenced.

Just last week, an overview study was published in the journal "The Lancet", in which 65 studies from 19 countries examined how good the protection against reinfection after corona illness is. It shows that no vaccine offers as good long-term protection as a previous infection. The catch is that you have to get infected first, and if you're not vaccinated, you're exposing yourself to an uncontrollable risk with an uncontrollable dose of virus.

The research also shows how quickly the protection of an infection against omicron decreases. While it remains high (more than 50 percent) up to the Delta variant for 75 weeks, with BA.1 from Omikron it drops below 50 percent after only 25 weeks and compared to BA.2 already after 10 weeks. But: the protection against serious illness remains high for 50 weeks at a minimum of 85 percent (no longer measured) - regardless of the variant. After infection with Omikron BA.1, vaccination with Biontech/Pfizer still offers about 50 percent protection against severe disease after 40 weeks - before Omikron, protection after this period was 80 percent.

The vaccination studies now show that booster vaccinations only provide extra protection against infection for a short time. Bivalent boosters, which are not based only on the original virus, perform better and indicate a weakness in the vaccination schedule with three of the same vaccines for Sars-Cov-2: the immune system attacks a variant or a virus segment so strongly that a later infection with omicron makes immune memory less flexible to update. This imprinting also occurs in natural infection.

A severe form of Long Covid is POTS, where patients feel dizzy and have an increased heart rate as soon as they sit up. A December Nature study found that this phenomenon is five times more common after infection than after vaccination. For Long Covid in general, experts estimate post-vaccination cases are in the order of a thousand. The vaccination itself reduces the risk of getting Long Covid after a later infection by about half. (aargauerzeitung.ch)