March 28, 2008

Colonial Smallpox Vaccine

Stupid Question ™
Dec. 6, 2001
By John Ruch
© 2001

Q: Regarding the demand for smallpox vaccine, why don’t we just make it the way the Colonists did? They were able to whip up plenty of vaccine without fancy equipment.

A: All vaccines are risky, their use being weighed against the risk presented by disease.

The Colonial smallpox vaccine had an abominable risk—1 to 2 percent of recipients died—but smallpox had a death rate of 25 to 30 percent. (A mild strain killed only 1 percent, and two virulent strains killed nearly 100 percent.)

Today, even the much safer modern vaccine is too risky for general use compared to the near non-existent chance of getting smallpox, which hasn’t been seen in the wild since 1977.

The Colonial method, first used in Boston in 1721, would be totally unacceptable today because it involved actually giving people smallpox. An arm or leg was cut open and pus from somebody else’s smallpox blister was inserted into the wound. With luck, recipients developed mild smallpox and produced antibodies that rendered them permanently immune to further infection. But some recipients developed lethal smallpox.

In 1796, English doctor Edward Jenner announced a new vaccine using pus from cowpox, a related but much milder disease that produced lesions on the udders of cows. This method was much safer but had drawbacks.

Cowpox doesn’t exist in the US and is rare in its European home. (Jenner once spent two years searching for a case of it.) Jenner had to ship threads soaked in cowpox pus to his US pals. And cows quickly get over cowpox, making it hard to maintain a reserve of the virus strong enough to use as a vaccine. (The disease is actually native to rodents.)

There were also health risks. Dr. Harrison Weed of the Ohio State University Medical Center notes there are recent reports of human deaths from cowpox in the UK. Also, direct cow-to-person vaccination was rare because of the rarity of infected cows and superstitions about being injected with animal tissue. Instead, most people were vaccinated with pus from another person’s cowpox blister—which led to the transmission of other bad diseases, including syphilis.

It was also common to misidentify a blister caused by another disease as being caused by cowpox, which led to other infections. Some people even fraudulently sold their smallpox pus as cowpox pus.

The current smallpox vaccine Dryvax, and another under development, use an extremely benign strain of a virus called vaccinia. Its origin is unknown, though it’s similar to both cowpox and smallpox (which is why it works).

It’s so weak that it doesn’t give permanent immunity, yet it’s still the most risky vaccine available in modern medicine, killing about one in 1 million recipients—and a higher portion of children.

That’s why, even if terrorists released smallpox, the government would vaccinate only those directly exposed (and possibly use the antiviral drug cidofovir as a stopgap).

Statistically, you could expect universal vaccination of everyone in the US to kill at least 300 people.

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