That multiple strains of COVID-19 coronavirus exist in different parts of the world probably won't impede vaccine development in the short term, experts told 鶹ý.
In a manuscript posted to the medRxiv preprint server, researchers reported finding multiple strains of SARS-CoV-2, the virus causing COVID-19. "It's not the exact same virus everywhere in the world," commented Harlan Krumholz, MD, of Yale University School of Medicine, in an exclusive 鶹ý video on the study.
This and similar findings raise concerns that COVID-19 may turn out to be like influenza, for which the predominant circulating strains change from one year to the next, such that vaccines must be reformulated annually -- and not always correctly.
While Richard Kuhn, PhD, of Purdue University, who was not involved with the research, pointed out that "more knowledge about strain diversification" may be incorporated into some successive "next-generation" COVID-19 vaccine, the immediately compelling goal is to develop a vaccine that works against at least one form of the virus.
"As far as COVID-19 strains, it's too early to be super concerned about strain variations and whether there is emergence of new strains and linkage to a vaccine," Kuhn told 鶹ý.
This is mainly due to the composition of a vaccine. Kuhn added "a vaccine is already presenting several if not numerous different sites on one of the surface proteins of the virus" where antibodies can be elicited. That's different from a typical antiviral drug, which has just one target.
"It's not going to be 'oh, this site we have, now it's changed because of this mutation that has occurred in this particular strain,'" he said. "Developing multiple targets for a vaccine to have antibodies against will reduce angst and anxiety."
Antivirals have received attention as therapeutic agents in the fight against COVID-19, but as Kuhn noted, developing a vaccine is not exactly the same process.
"If it's a single antiviral, then resistance occurs sometimes pretty quickly," he said. Because of this, only a "cocktail of antivirals" helped achieve significant progress against the HIV and hepatitis C epidemics in many cases.
When thinking about viruses that can mutate, particularly those that need new vaccines every year, influenza comes to mind. However, Kuhn noted the structure of the coronavirus itself compared to influenza as a key reason to hope one working vaccine may be enough when it comes to COVID-19.
The coronavirus is "all encoded on single RNA molecule," whereas the influenza virus has eight different segments of RNA, he noted. Two of these, hemagglutinin (HA) and neuraminidase (NA), are responsible for the annual variations that require new vaccines.
Kuhn expanded on these ideas of "shift and drift." The former refers to genetic recombination that may lead to increases in infectivity and/or virulence, while "drift" is mutations in key proteins that may allow the virus to evade antiviral drugs and vaccine-induced immunity.
"A coronavirus has different mechanisms for recombination, but it's not going to be as significant or as severe as the flu," Kuhn said.
Maria Elena Bottazzi, PhD, of Baylor College of Medicine, said further studies are needed to determine whether different strains of SARS-CoV-2 could undermine vaccine efficacy.
"Based on the [medRxiv] paper it is unclear if any mutations are having any bearing on infectivity, severity or transmission. At the very minimum, the authors could have checked whether the one mutation they mention in the S-protein is really leading to an amino acid change that is likely to affect the ACE2 receptor binding or not," she said in an email to 鶹ý. ACE2 appears to be the portal through which the COVID-19 virus enters host cells.
Currently, is underway in the U.S.; another in China with a different product was announced shortly afterward.