What if you received smallpox vaccination years ago?

Factual Questions
1

Many (most?) Baby Boomers have already been innoculated against smallpox. They have the scars on their arms to show it. So, would they need to be re-innoculated? Is that vaccination still effective after 30-40 years?

2

The Master speaks:

How long does a smallpox vaccination protect you?

3

I was vaccinated as a wee tot in '71, according to my parents. I have no scar.

When entering the US Army in '87, I was weak-live-virus vaccinated again. I was the only one in the company (of about 120 recruits) to have absolutely no reaction (not even a touch of redness) at all. They were diligent about checking for reactions, specifically overreactions, as it was thought that if you’d had any sort of immune deficiency (i.e. undiagnosed AIDS) you were sunk.

So either I’m just immune, or the rumors are true (from the column):

-AmbushBug
[sub]i am the astro-creep[/sub]

4

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.