How does the dangerousness of the novel coronavirus Sars-CoV-2 develop when it circulates in the population over the long term? Based on comparisons with other, long-known coronaviruses, a research team suspects that Covid-19 will gradually turn into a harmless cold in a few years. The prognosis is based on the assumption that infections are mild in childhood and offer partial protection against severe courses in later life. If this is not the case, vaccinations against the virus will continue to be necessary in the long term, the researchers said.
In addition to the Sars-CoV-2 coronavirus, which is currently responsible for a worldwide pandemic with numerous fatalities, there are other coronaviruses that have long been found in humans. Four of them are common worldwide and usually only cause mild cold symptoms. These four coronaviruses are endemic, which means they circulate continuously in the population and cause frequent infections. Children typically come into contact with these viruses at preschool age.
Comparison with endemic coronaviruses
A team led by Jennie Lavine from Emory University in Atlanta is now using findings about these harmless coronaviruses as a basis for predicting how Sars-CoV-2 will develop in the next few years if it is also so widespread in the population that it is becomes endemic. With the endemic coronaviruses known to date, infections in childhood generally proceed without complications and offer a certain, albeit limited, immunity to the respective virus.
“Re-infection is quite possible within a year, but even if it does occur, the symptoms are mild and the virus is cleared from the body faster,” says Lavine. “This underscores the need to distinguish the various components of immunity to Sars-CoV-2: How long does the immunity that prevents a severe course last and how long does the immunity that prevents transmission last? These periods of time can be very different. “
Infectious mortality could decrease in the long term
With regard to Sars-CoV-2, there are already some studies on these questions, but no clear answers yet. For their model, Lavine and her colleagues assume that the values ​​roughly correspond to those of the common cold coronavirus. Accordingly, the initial infection would offer a certain protection against severe courses, but not against renewed infection and transmission. According to the researchers, the harmlessness of the four endemic coronaviruses could be due to the fact that almost all people acquired basic immunity as children. “We don’t really know what it would be like if someone got one of the other coronaviruses for the first time as an adult instead of as a child,” says Lavine.
If previous observations and assumptions are confirmed, according to which Sars-CoV-2 also has a mild course in children and protects them from severe forms of the disease in later life, the long-term infectious mortality rate could drop below 0.1 percent and thus below the value of seasonal influenza fall, according to the researchers. “We are in uncharted territory, but an important message from the study is that immunological indicators suggest that death rates and the critical need for widespread vaccination may decline in the future,” said co-author Ottar Bjornstad of Pennsylvania State University . “Therefore, the maximum effort should be aimed at the goal of surviving this virgin pandemic on the way to endemic.”
Tests continue to be important
In order to endanger as few human lives as possible in this way, it is important, according to the researchers, to slow the spread of the disease through social distancing measures and, as soon as sufficient quantities of the vaccines are available, as many people as possible to use them vaccinate. According to the researchers’ model, mass vaccinations are especially important in the first year or two. Afterwards, when the virus reaches an endemic status, vaccinations are presumably only necessary for risk groups.
Comprehensive testing, on the other hand, is still extremely relevant, the researchers write. Especially if the virus actually becomes more harmless over time, as assumed in the model, it will soon no longer be distinguishable from other infections based on the symptoms. Even so, data on the spread is important to monitor the progress of the pandemic in transition to endemic. All prognoses are based on the fact that an infection with Sars-CoV-2 is actually more harmless in children and protects them from later severe courses. If this assumption turns out to be incorrect and the virus may become more dangerous for children over time, permanent mass vaccination programs that include children are required, the researchers said.
Source: Jennie Lavine (Emory University, Atlanta) et al., Science, doi: 10.1126 / science.abe6522