Three Swedish professors of virology, Lennart Svensson of Linköping University, Åke Lundkvist of Uppsala University and Anders Widell of Lund University, have concluded that even a very high vaccination rate of more than 90 percent doesn't fully stop the spread of COVID-19 infection, as witnessed by examples across the globe.
“Everything indicates that SARS-CoV-2 will remain, as a recurring seasonal virus. Herd immunity will be very difficult or even impossible to achieve,” the authors wrote in an opinion piece in the newspaper Dagens Nyheter.
According to the professors, four coronaviruses that infect humans and return during the winter season, causing mild colds, have been known to mankind for a long time. What's more, since 2003 humanity has been affected by two completely new coronaviruses that can cause very serious infections: SARS-CoV-1 (with mortality about 10 percent) and MERS-CoV (mortality about 34 percent).
However, the novel coronavirus will not be eradicated, either through natural immunity or vaccination-achieved herd immunity, as only viruses that have humans as their unique host can be completely eliminated, they wrote, citing the complete vaccine-driven elimination of smallpox in the Seventies.
By contrast, for animal viruses to cross boundaries and jump species, mutations are required, often resulting in a speedy spread at the cost of pathogenicity. The new SARS-CoV-2, like the four seasonal coronavirus types, has shown global spread and probably reduced mortality over time, they mused.
“Thus, everything points to SARS-CoV-2 becoming an endemic, which is why we must learn to live with this virus,” the professors wrote.
However, history suggests that it will take many years before SARS-CoV-2 loses its potency and becomes a seasonal coronavirus, they argued, citing OC43 (HCoV-OC43), which was probably adapted from a livestock coronavirus to humans sometime in the 1890s and was first detected in 1967 in children with cold symptoms.
In the meantime, the novel virus will continue to mutate. “Individual virus variants have an increased ability to spread, and most are not not passed on because of the fact that the new mutations are not sufficiently beneficial for the virus”, the professors explained.
Today's vaccines will, however, provide protection against severe and mild infections caused by the variants which are known at present, although the professors stressed that vaccines are unlikely to provide longer-lasting protection than a natural infection.
“Crucially, immunity against respiratory viruses, including coronavirus, whether created by an infection or by vaccination, appears to be very short-lived,” the Swedish professors concluded.