How Do We Know a COVID-19 Vaccine Will Work?

For reasons I am not sure about, I keep reading the Journal-News, the newspaper of Butler County, Ohio. And in a recent thread, it has come up that they do not believe a COVID-19 vaccine will work since influenza vaccines do not work. The problem with this is, influenza vaccines work incredibly well. The problem is, influenza sees it coming and has a defense. Understanding why this is different between influenza and COVID-19 is important.

Influenza changes VERY rapidly, through two mechanisms. The first, “antigenic drift,” are “small mutations in the genes of influenza viruses that can lead to changes in the surface proteins of the virus.” Those surface proteins are what your immune system recognizes. The second, “antigenic shift,” is a “major change in an influenza A virus proteins” in influenza viruses that infect humans. Either of these changes create a new strain that is not recognized by the immune system. The influenza vaccine works very nearly perfectly against the strains inoculated against. You go and screw it up by getting the wrong influenza. Evolution sucks when you are on the short end of it.

For reasons relating to evolutionary pressures, betacoronaviruses do not mutate quickly. Really, they don’t mutate much at all. Betacoronaviruses mutate so slowly, that while there are thousands of known influenza strains that affect humans, there are only handful of known betacoronaviruses that can infect humans. The three most interesting are: SARS-CoV, which caused the SARS outbreak in 2003; MERS-CoV, which caused the MERS outbreak in 2012, and SARS-CoV-2, which causes COVID-19. There are a handful of genetic variants known of SARS-CoV-2, but none are so different as to introduce a new strain. This is all a good thing, because it is why we know a COVID-19 vaccine will work very effectively.

And you know how we know it will work? Look at the measles vaccine. There’s only one viruses that causes measles (Measles morbillivirus), and the vaccine against it is nearly perfectly effective. It has to be. Measles is so contagious, an effective immunity rate of 95% is necessary to prevent the spread of measles. And the vaccine works.

Look at the smallpox vaccine. There are two viruses that causes smallpox: Variola major and Variola minor. Smallpox is slightly less contagious than measles, and that means only an 80% effective immunity rate is necessary to stop community spread. But not only did the smallpox vaccine work, global eradication of smallpox is mankind’s greatest accomplishment. In fact, it worked so incredibly well, many have forgotten what it a world with that kind of disease is like.

I can repeat all of the above about polio.

Yeah, I will be first in line to get the COVID-19 vaccine, when it is available.