So last few years I’ve had flu shots only to later learn that the epidemiologists picked the wrong strains and the flu shot was not effective !!
In light of the above, what’s the confidence in current Covid-19 models ? Is there any model validation report available online ?
With flu shots, you absolutely need a crystal ball. The development of the yearly flu vaccine must be started 12 to 18 months before the flu season.
Epidemiologists study the minor outbreaks throughout the world, and they watch how each strain spreads. Based on that information, somebody somewhere figues out which strain will become most prevalent during the flu season 18 months later.
Coronaviruses are worldwide, come in many flavors, and infect many animal species. They also mutate rapidly.
Epidemiology is not an exact science. Tracking infections gives a picture of how they will spread in the future.
~VOW
First of all, it is wrong to say that “the flu shot was not effective !!“ Even in years where epidemiologists do not identify the most prevalent strains, the influenza vaccine still provides a measurable degree of protection in reducing the virulence and duration of an influenza infection.
Virologists and epidemiologists largely rely upon tracking and surveillance of influenza strains for both Type A and Type B genuses that occur the previous year and in the opposite hemisphere (since influenza is typically a ‘seasonal’ virus). This gives them clues as to which strains are most likely to be prevalent but because of the almost unique ability of influenza to recombine between strains in both humans and domestic animals to produce a new novel strain, it is never possible to fully characterize all possible variants nor to assess the effectiveness of vaccines prior to flu season. The vaccines themselves are in a constant state of development since the same strains (or strains derived therefrom) tend to repeat over and over, which is the reason we can have a vaccine (often multivalent vaccines designed to protect against several strains) every year rather than having to wait the three or more year period that is typical for vaccine development.
This question is kind of like asking why one car company can’t produce a line of cars that everybody wants to buy. In theory, Toyota could make the perfect truck, sedan, hybrid, minivan, and sports car that should satisfy the entire market (and indeed, they’ve tried) but plenty of buyers are going to come along wanting something bigger, or smaller, or in a different color, or with a larger trunk, et cetera so there are a vast array of different makes and models on the road. Influenza Type A is the same; it divides itself into multiple “makes” (various permutations of hemagglutinin and neuraminidase) and then various models within those makes (strains), each of which have a characteristic antigen presentation and immune response. On a good year, epidemiologists guess correctly enough that a vaccine has an effective ability to attenuate severe cases by 60% to 70%, but even in a bad season (which 2019-20 was) the reduction in severe morbidity and mortality was still >40% (CDC: “Interim Flu Vaccine Effectiveness Estimates for the 2019-20 Flu Season Show Flu Vaccines Providing Substantial Protection, Especially in Children”).
There are no current models to predict the efficacy of a SARS-CoV-2 (the virus that causes COVID-19) vaccine because there is no qualified vaccine, nor enough knowledge to know how SARS-CoV-2 will vary over time.
Stranger