One of the trickiest parts of containing the COVID-19 pandemic with vaccines has been keeping up with mutations. Variants from the virulent and deadly delta to the mercifully short-lived mu proved to be able to evade some of the existing vaccines' defenses, as current vaccines were created to fight against earlier iterations of the virus. For instance, AstraZeneca's COVID-19 vaccine was found to be 74.5% effective against the initially-detected alpha variant, whereas the same vaccine proved only 67.0% effective against the delta variant.
Indeed, virus' mutations thus create something of an arms' race between humans and viruses. Influenza is a prominent example of such an arms race: every year pharmaceutical companies develop a new flu shot for the latest mutation, and every year a new mutation spawns for which new vaccines must be developed.
So it makes sense that the holy grail of vaccines would one that could defend against all variants of a category of virus. That dream, according to the researchers behind a recent paper in the Journal of Clinical Investigation, could one day become a reality — at least for coronaviruses.
Scientists from Northwestern Medicine have discovered that people who develop immunity to one species of coronavirus — be it immunity through vaccination, or because of a natural infection — often have broad immunity against similar coronaviruses. Patients with prior coronavirus infections possessed immunity that partially protected them from infections caused by different coronaviruses. Similarly, antibodies extracted from humans who had been vaccinated against SARS-CoV-2 showed that they had some protection from coronaviruses like one that causes a type of common cold (OC43), as well as some protection against a close relative of SARS-CoV-2, SARS-CoV-1 (colloquially known as SARS).
The correspondence between vaccination for one coronavirus, and protection against others, also appeared in other animals. Mice that received a vaccination against SARS-CoV-1 had immune protection from intranasal exposure to SARS-CoV-2.
The idea of a universal coronavirus vaccine has tantalized public health experts for years. Such viruses are the cause of many pandemics across different species, including humans and birds. A type of RNA virus, coronaviruses are known for the club-like spikes that jut out from the exterior of their spherical center. There are three species of coronavirus that can cause diseases in people: Embecoviruses, often responsible for common colds; merbecoviruses, which are responsible for MERS; and sarbecoviruses, which includes SARS-CoV-1 (the virus behind the 2003 SARS outbreak) and SARS-CoV-2.
These three different coronavirus families are so unique that it is unlikely a single vaccine could fight species within all three groups, scientists say. Yet this latest study suggests that a day may come when one vaccine is effective for every species within each family.
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"These findings provide the first demonstration that coronavirus vaccines (and prior coronavirus infections) can confer broad protection against heterologous coronaviruses, providing a rationale for universal coronavirus vaccines," the authors conclude.
"Our study helps us re-evaluate the concept of a universal coronavirus vaccine," lead author Pablo Penaloza-MacMaster, assistant professor of microbiology-immunology at Northwestern University, explained in a statement. "We might end up with a generic vaccine for each of the main families of coronaviruses, for example a universal Sarbecovirus vaccine for SARS-CoV-1, SARS-CoV-2 and other SARS-related coronaviruses; or a universal Embecovirus for HCoV-OC43 and HKU1 that cause common colds."
Penaloza-MacMaster also told The Denver Channel that, while existing vaccines target the spike protein on a coronavirus' shell that helps it enter cells, a universal coronavirus vaccine might take a different approach. One possibility would be to target the interior of a coronavirus, such as by attacking the nucleocapsid in the virus sphere. Other research conducted by Penaloza-MacMaster and his team suggests that this approach can both confer broader protection and help prevent breakthrough cases.
A vaccine development foundation in Norway is currently giving $200 million in grants to scientists working on a universal coronavirus vaccine. In addition to Northwestern Medicine, there are scientists trying to develop universal coronavirus vaccines at the University of Virginia, UNC Chapel Hill and the University of California–Irvine.