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50% efficacy in an individual could still have a dramatic effect on the overall infection rate. The purpose of getting vaccinated is not to protect you, it is t

50% efficacy in an individual could still have a dramatic effect on the overall infection rate. The purpose of getting vaccinated is not to protect you, it is to protect the community. If each of the people with whom you come in contact has their likelihood of being infected reduced by 50%, your chance of being infected may be reduced by much more than that. I don't know what the relationship is between vaccination efficacy and infection rate in this specific case, but on its own a low-ish individual efficacy does not mean a vaccine isn't worth using.

beagle3 14y ago
That is true. Now, vaccines DO sometimes have complications - last time I got a vaccine (tetanus, 8 years ago), my elbow got swollen to about twice its size and was hard to bend. They weren't sure what went wrong (contaminated vaccine, parasitic infection, ??) but I had to take a two week course of antibiotics (which carries its own problems ...) I'm sure at the herd level, 50% efficacy for individual vaccines is great. But on a personal level, I can't find any analysis that takes into account both efficacy ("value") and complications ("price"). And on a personal note, I have the flu maybe once in ten years (if even that), despite hanging around people who get it regularly -- which is why I don't even consider getting a flu vaccine. There is almost no research about how to improve general immune function, and I believe results on that front would be much more useful than a 50% efficacy vaccine.
stan_rogers 14y ago
The "50% efficacy" doesn't indicate that the vaccine provides 50% effectiveness in blocking a particular influenza; rather it stems from the fact that the particular influenza(s) being targeted might not be the ones passing through an area. "The flu" is an umbrella term for a number of different infectious strains (that mutate), and the object of the game is to detect early on which virulent, dangerous and uncommon strains (already active elsewhere) are most likely to spread widely and vaccinate against them. Frequently, less-virulent strains to which a large percentage of the population has already been exposed will be ignored (hitting somebody with hundreds of strains to develop immunity to simultaneously reduces the effectiveness of the vaccine for all of them). And there's always the chance that a particularly nasty strain may become epidemic after this year's vaccine has been formulated and distributed (in which case, there may or may not be an effective vaccine available in time for people to develop immunity to that strain). So even though you have been effectively vaccinated against the targeted strain(s), you can still contract other strains. And you may have a miserable time dealing with something you did catch, which can keep you from thoproughly enjoying the fact that you didn't catch something that may have been many, many times worse.
azov 14y ago
Actually, it is even more dramatic. Infection rate is essentially binary: either the disease spreads (which means the number of sick people goes up until pretty much everyone in the community who is not immune gets it - this is called epidemic) or the number of sick people decreases and the disease dies off. There is a tipping point depending on the percentage of people who is immune. For common flu you need to have 50-70% vaccinated to prevent epidemic (its basic reproduction number, R0 per wiki article, is between 2 and 3). http://en.wikipedia.org/wiki/Mathematical_modelling_of_infectious_disease http://en.wikipedia.org/wiki/Mathematical_modelling_of_infec...

beagle3 14y ago

That is true. Now, vaccines DO sometimes have complications - last time I got a vaccine (tetanus, 8 years ago), my elbow got swollen to about twice its size and was hard to bend. They weren't sure what went wrong (contaminated vaccine, parasitic infection, ??) but I had to take a two week course of antibiotics (which carries its own problems ...) I'm sure at the herd level, 50% efficacy for individual vaccines is great. But on a personal level, I can't find any analysis that takes into account both efficacy ("value") and complications ("price"). And on a personal note, I have the flu maybe once in ten years (if even that), despite hanging around people who get it regularly -- which is why I don't even consider getting a flu vaccine. There is almost no research about how to improve general immune function, and I believe results on that front would be much more useful than a 50% efficacy vaccine.

stan_rogers 14y ago

The "50% efficacy" doesn't indicate that the vaccine provides 50% effectiveness in blocking a particular influenza; rather it stems from the fact that the particular influenza(s) being targeted might not be the ones passing through an area. "The flu" is an umbrella term for a number of different infectious strains (that mutate), and the object of the game is to detect early on which virulent, dangerous and uncommon strains (already active elsewhere) are most likely to spread widely and vaccinate against them. Frequently, less-virulent strains to which a large percentage of the population has already been exposed will be ignored (hitting somebody with hundreds of strains to develop immunity to simultaneously reduces the effectiveness of the vaccine for all of them). And there's always the chance that a particularly nasty strain may become epidemic after this year's vaccine has been formulated and distributed (in which case, there may or may not be an effective vaccine available in time for people to develop immunity to that strain). So even though you have been effectively vaccinated against the targeted strain(s), you can still contract other strains. And you may have a miserable time dealing with something you did catch, which can keep you from thoproughly enjoying the fact that you didn't catch something that may have been many, many times worse.

azov 14y ago

Actually, it is even more dramatic. Infection rate is essentially binary: either the disease spreads (which means the number of sick people goes up until pretty much everyone in the community who is not immune gets it - this is called epidemic) or the number of sick people decreases and the disease dies off. There is a tipping point depending on the percentage of people who is immune. For common flu you need to have 50-70% vaccinated to prevent epidemic (its basic reproduction number, R0 per wiki article, is between 2 and 3). http://en.wikipedia.org/wiki/Mathematical_modelling_of_infectious_disease http://en.wikipedia.org/wiki/Mathematical_modelling_of_infec...