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As part of COVID-19 discussion, I’ve heard a lot of people voice skepticism about flu shots. I think there is a misunderstanding about the #FluShot. #covid #Trump
Simply put: You don’t get the flu shot for you, you get it to prevent the flu from killing your grandmother.
Simply put: You don’t get the flu shot for you, you get it to prevent the flu from killing your grandmother.
Flu shots on any given year ‘might’ prevent you from getting the flu, and ‘might’ shorten the length you have the flu if you do get it. So there will be lots of people who get flu shots who get the flu.
You might ask why is it worth the trouble if it only ‘might’ prevent me from getting the flu or only ‘might’ shorten the duration?
~20-60k people die yearly of the flu in the United States, mostly the elderly. We get the flu shot not for ourselves - which on any given year doesn’t have a great rate of preventing the flu entirely at the individual level - but to prevent spread across the population.
There is an index of transmissibility/virulence known as the R0 number. The R0 number is the number of people someone who had a virus goes on to infect.
COVID-19 has been a concern because early estimates of its R0 were between 2 and 4. Taking a mid-value of 3, this means if at week one 1 person was infected, at week two 3 people are infected, at week three 9 people are infected, at week four 27 people are infected and so on.
At week sixteen the number of people infected are 3^16, or ~43 million. It gets out of control really fast. And although it doesn’t seem so bad the first month, by the third and fourth month it quickly becomes a debacle, as is the nature of exponential growth curves.
Now if through social distancing we get the R0 from 3 to 2, the situation becomes a ridiculous amount better. This means if at week one 1 person was infected, at week two 2 people are infected, at week three 4 people are infected, and at week four 8 people are infected.
At week sixteen only 2^16 people are infected; meaning only ~65K people for an R0 of 2 compared to 43M for an R0 of 3. Just changing the R0 from 3 to 2 makes an insane difference across the population (nearly 100x).
The study I’ve posted below gets into the data of direct (benefits to you) vs indirect (benefits to the elderly) over the last 10 year of flu shots in Germany.
They find that just by lowering the R0 a little across the population, flu shots dramatically protected elderly lives. But it only works if most of us do it.
“indirect vaccination effects are bigger than direct ones if the effective reproduction number of disease transmission is close to the critical value of 1...”
“... Simulation results for 20–60% vaccination with live influenza vaccine of 2–17 year old children in Germany, averaged over 10 years (2017–26), confirm this result:...”
“... four to seven times as many influenza cases are prevented among non-vaccinated individuals as among vaccinees...”
“... For complications like death due to influenza which occur much more frequently in the unvaccinated elderly than in the vaccination target group of children, indirect benefits can surpass direct ones by a factor of 20 or even more than 30.”
