Adverse reactions to smallpox vaccinations

I’ve searched for smallpox, and found lots of threads (e.g. here and here, and Cecil’s column, which quotes about 300 deaths if the US were vaccinated against smallpox), mostly about whether previous smallpox vaccinations are still any good (short answer: maybe a little. They’re not really sure.).

Are those of us who were vaccinated previously less likely to die from being vaccinated again? I survived it once, so if I was somehow sensitive, I’d have suffered then (which I didn’t). Is any such difference taken into account in the 300 expected deaths figure? Similarly for about annual flu shots; is each shot a new roll of the dice, or does surviving the first one mean I’m less likely to die from later ones? Conversely, is there a chance of becoming sensitized by previous vaccinations, making me more likely to suffer?

One last question: They’re talking about dilluting the existing vaccine by a factor of 5 or 10 to extend it. Will this have any effect on the death or “adverse reaction” rates?

"…mostly about whether previous smallpox vaccinations are still any good (short answer: maybe a little. They’re not really sure.). "

Perhaps the best relevant data are those assembled by Tom Mack to address the question of whether having been vaccinated in the distant past is likely to protect you from death as opposed to disease (Mack TM. Smallpox in Europe, 1950-1971. J Infect Dis 1972;125:161-9). The data are assembled from reports of smallpox outbreaks in Europe 1950-1971. The table below shows the relationship between years since vaccination and death for smallpox patients of all ages:

yrs since
vaccination | cases | deaths | survivors | fatality (%)
<10 | 72 | 1 | 71 | 1
11-20 | 43 | 3 | 40 | 7
20+ | 297 | 33 | 264 | 11
never | 79 | 41 | 38 | 52
Perhaps the most relevant data are those for older people vaccinated 20+ years ago (since, in the U.S., there are almost no younger vaccinated people or people vaccinated <20 years ago. This table includes data only for people 50+ years of age vaccinated 20+ years ago:

yrs since
vaccination | cases | deaths | survivors | fatality (%)
20+ | 96 | 25 | 71 | 26
never | 11 | 10 | 1 | 91

As you can see, the numbers are not large, however, these data do simultaneously suggest that 20-year old vaccinations provide significant protection against fatal infection but that the protection they provide is not nearly enough.

“Are those of us who were vaccinated previously less likely to die from being vaccinated again?”

Yes. Most people who die from vaccination with vaccinia virus have some immune defect. If you survive it once you probably don’t have such an immune defect (unless, of course, you acquire an immune defect from cancer treatment, AIDS, organ transplant, etc.).

“Is any such difference taken into account in the 300 expected deaths figure?”

I expect so. Whose “300 expected deaths figure” are you referring to?

“Similarly for about annual flu shots; is each shot a new roll of the dice, or does surviving the first one mean I’m less likely to die from later ones?”

Flu vaccine contains no “live” virus and, unlike smallpox vaccination, does not cause any infection. The main contraindication to flu shots is hypersensitivity to any of the vaccine components, e.g., egg protein. AFAIK, most people who are hypersensitive to eggs develop their hypersensitivity from eating eggs, not from getting flu shots. I suppose it could be possible to develop a hypersensitivity to flu vaccine components but I haven’t heard of it.

“Conversely, is there a chance of becoming sensitized by previous vaccinations, making me more likely to suffer?”

Yes. This is why you shouldn’t have routine tetanus boosters more often than every 10 years. (I think that becoming sensitized may also be a problem with human rabies vaccine.)

“They’re talking about dilluting the existing vaccine by a factor of 5 or 10 to extend it. Will this have any effect on the death or “adverse reaction” rates?”

I doubt it. Smallpox vaccine is live vaccinia virus. Either you get an infection (a “take”) or not. With luck, you get an infection which runs its course and you are left with a scar and immunity to smallpox. With bad luck, either nothing happens (and you have no immunity) or you get an infection that your body has trouble controlling which can be fatal.

Diluting the vaccine just reduces the chances that you will get a “take.” Once you get a “take,” the consequences should be the same regardless of whether you were inoculated with a standard dose of virus or one fifth of a standard dose.

Cecil’s (see link in the OP).

Thanks for the detailed response.

I’d like to mention a futher bit about the adverse reactions to smallpox vaccine.

Fatal reactions are pretty thoroughly documented in connection with active herpes (either genital or oral) and active eczema. Either of which can occur in young or old. There is a treatment for these reactions, which reduce the death rate to a “mere” 30% (as opposed to nearly 100% for untreated). And, since you can acquire either condition post-first vaccination, surviving the first is not a garauntee you will survive a second.

And there were always a certain number of people who just plain had a nasty reaction, for no reason that could be determined. Which is true of any vaccine, but smallpox is considered one of the more hazardous vaccines we have. The complication and death rate was tolerable only because smallpox itself was so much more horrible.

BUT - for the vast majority of humanity a smallpox vaccine should be just a couple days of slight fever and a nasty blister, followed by a permanent round scar. (If you don’t know what one of those look like ask someone over 35 to show you theirs)