The news this morning mentioned that health officials had misjudged the particular strains of flu that would be most prevalent this winter, and as a result the flu vaccine that has been/is being administered is only “10% effective.”
What does “10% effective” mean? Does it mean that if a typical unvaccinated person has a 30% chance of contracting the flu, getting vaccinated will result in only a 27% chance of getting the flu?
It means the vaccine might only cut one’s risk of getting influenza by 10%.
“Might”, because this estimate is based on what just happened during Australia’s influenza season. and because experts think the same thing is likely to occur in the U.S.
The expected mismatch between the dominant circulating flu strain and the vaccine strain is said to be due to a mutation occurring in the vaccine strain during growth in eggs.
We’re still at least several years away from an approved “universal” flu vaccine, which would protect against multiple strains and due its genetically engineered production, would not be susceptible to mutating in this fashion.
And how does one define “ineffective”? As I understand it, even if you get the wrong flu vaccine, it’ll probably still decrease the severity and duration of the symptoms, because all flu viruses share at least some degree of similarity.
The ‘flu vaccine’ contains 3-5 strains of influenza, and gives you increased immunity against those particular strains.
The vaccine being given this fall was manufactured starting about last March or April.
Influenza experts made their best guesses as to which strains would be the most likely for the 2017-2018 flu season, and those were the strains included in the vaccine.
If different strains are the ones that start spreading this fall & winter, than the vaccine won’t provide much protection against them – some, but not much.
I presume that “10% effective” means that only 10% of the influenza cases seen thus far (in Australia) are from one of the strains included in this year’s vaccine – 90% are from other strains that weren’t included in the vaccine.
(I’m not sure how they account for the likelihood that the strains included in the vaccine were prevented by the vaccine, or the people who got them didn’t get sick enough to have to see a doctor. Seems like that would make it hard to get an accurate result. How do you count the number of people who would have gotten sick, but didn’t, because they got the vaccine?)
Ok, so out of all the patients reporting the australian health clinics with the flu, out of those patients, which ones had strains the vaccine protects against?
That number is apparently 10%. This assumes no cross-protection. There might be a little bit but I guess it’s not much.