Timeline Of Early COVID-19 Events
Trump’s Treatment

Will A COVID-19 Vaccine Be Effective?

In an earlier post made in late May, your humble blogger predicted that the major hurdle in controlling the CoV-2 pandemic was not in developing an effective vaccine, but in getting enough people to be vaccinated. A recent poll from the Kaiser Family Foundation supports that notion. 54% of respondents said they would not get the vaccine if it was available for free before the November 3 presidential election. I also posited that that time frame for developing a vaccine is untenable. I would like to see a poll on how many people would refuse a vaccine that was approved and released, say in April next year, which is a more tenable timeframe. Given the absurd anti-vaccination sentiment in the US, I am not optimistic that the response would be much better.

A population needs about 70% of its people to carry protective immunity in order for herd immunity to be effective. It is unreasonable and unethical to reach that 70% threshold via natural infection with a novel pathogen like CoV-2 that causes debilitating disease that we currently do not know how to effectively treat. Therefore, a vaccine that confers a similar level of immunity, but without the risks associated with the disease, is the only way to ethically attempt to achieve a population-wide protective herd immunity. But, if too few Americans get a Covid-19 vaccine when it becomes available, it won't help reduce the spread of the virus making the whole vaccine development effort largely moot, at least for the next two or three years.

In any infectious disease outbreak, the critical factor for controlling it is the “R naught” or R0 number, which is a measure of how contagious the pathogen is. For seasonal flu, R0 = 2, meaning that on average, an infected person will infect two others, thereby increasing the viral spread. For CoV-2, R0 = 4, which means that on average, an infected person will infect four others, twice the infection rate of flu. During an infectious disease outbreak, the goal of public health officials is to get the R0 value to <1, which signifies that the infection is petering out. The only ways to achieve this are to 1) wait for seasonal viruses to run out of their season, 2) via quarantine to limit exposure and spread, 3) vaccination to confer herd immunity, 4) natural infection to achieve herd immunity, or 5) using anti-pathogen medicines such as antibiotics. For a pathogen like CoV-2, for which there are no good medicines, or a vaccine to reduce the R0 value, or for which there does not seem to be a seasonal limit, and for which natural infection is not ethical, #2, or isolation, is the only way to reduce disease spread. Facemasks are an effective way to isolate and prevent spread of respiratory pathogens. In fact, researchers in the UK predict that if just 50% of people wore face masks, the CoV-2 R0 would drop to <1, buying us time until we can develop an effective vaccine with which to achieve a more permanent herd immunity. But, that can only happen if enough people get vaccinated. That will be the great impediment.

We will see.

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