Prof. Ruth Arnon: Lessons from influenza

With infections, as with football, a best offense is often a good defense. But while that strategy works for many infectious diseases, it doesn’t work with influenza; thanks to its readiness to mutate, the influenza virus effectively “shifts the goalposts” each year, requiring a new vaccination.

Renowned Weizmann Institute immunologist Prof. Ruth Arnon is spearheading a new defense—a universal influenza vaccine that is currently in Phase III of the clinical trial process—that focuses on the parts of the virus that stay the same from year to year, gluing the goalpost to the ground once and for all.

Prof. Arnon, who emphasized that she is not an expert on coronavirus, says she thinks a similar strategy might also be a useful one countering coronaviruses, including the current COVID-19 strain.

That is, a possible pharmaceutical approach to creating a vaccine against COVID-19 involves targeting a particular viral protein, called SPIKE, which is an important offensive player in the virus’s infection game. Another approach would be targeting a protein, or segments of the virus proteins, that are common across the most virulent types of coronavirus, including SARS-CoV, MERS-CoV, and COVID-19.

“If I were working in the coronavirus field,” says Prof. Arnon, “this non-changing protein approach is where I would focus my efforts.”

How long will it take to devise a vaccine?

But it’s going to take patience. Even if a universal coronavirus vaccine were identified today, it is unlikely to be of use this year. Why will it take so long?

Part of the challenge is one that is common to all vaccine production processes. Vaccines must be tested in animals, but there are no good animal models of how the COVID-19 infection cycle works in humans, which means preclinical trials will likely have to be carried out. Moreover, a vaccine must be tested in people for safety—a process that can take weeks to months. And then, once a vaccine is identified, it must be produced in sufficient mass quantities—and administered far and wide—in order for herd immunity to take effect. Herd immunity is a form of indirect protection that occurs when a large percentage of a population has become immune to an infection, thereby providing a measure of protection to individuals who are not vaccinated. In effect, the virus runs out of hosts. Furthermore, vaccine trials tend to take longer than trials for, say, cancer drugs; the vaccines are administered to healthy people, and efficacy can only be determined through a painstaking “wait and see” approach, to find out whether the vaccines indeed fend off infection.

So, notes Prof. Arnon, it isn’t enough to generate a vaccine—it has to be delivered to everyone at risk in order to be truly effective. For COVID-19, that’s the whole world. By the time that happens, the current outbreak may have worn out by itself.

Will coronavirus be a seasonal, or periodic, illness?

It’s also not clear whether, if a vaccine is developed for COVID-19, coronaviruses will have a seasonal fluctuation and die out like influenza, which is what happens to the flu, thanks to the herd immunity caused by the seasonal flu vaccine, as well as the arrival of warmer temperatures to which the virus is ill suited.

Coronaviruses are a common type of virus, and they come in a variety of strains. Most of these strains produce the mildest of cold symptoms in the infected individual. From time to time—and with frustrating unpredictability—a virulent variety appears, such as the SARS coronavirus (SARS-CoV) strain of 2003, MERS-CoV in 2012 (both of which petered out by summer) and most recently, COVID-19. If COVID-19 sticks around, or if it decides to keep re-appearing like influenza, having a vaccine will be crucial.

A universal coronavirus vaccine may not help us win the current outbreak, but, says Prof. Arnon, it would help us mount the best defense for the future.

Prof. Ruth Arnon is supported by the Irwin Green Alzheimer's Research Fund and the Estate of Ethel Lena Levy.