Smallpox vaccine

From Wikipedia, the free encyclopedia

Smallpox vacinne being administered.

The smallpox vaccine was the first successful vaccine ever to be developed and remains the only effective preventive treatment for the deadly smallpox disease. It was first perfected in 1796 by Edward Jenner who acted upon the observation that milkmaids who caught the cowpox virus did not catch smallpox.

1 Before smallpox vaccine
2 Early Vaccination
3 Eradication of smallpox
4 Use of vaccine currently
5 See also
6 Notes
7 External links

[edit] Before smallpox vaccine

Before the smallpox vaccine there was no hope for those with smallpox. Historical records show that a method of inducing immunity was already known. The more hazardous variolation or inoculation – inoculation with smallpox pustules themselves – had been practiced throughout the latter half of the 17th century by physicians in India, China, Turkey, Persia, and Africa. One document in particular Essay on External Remedies 1715 by a Dr. Kennedy, who was doing research in Constantinople, documented physicians there:

"...scarred the wrists, legs, and forehead of the patient, placed a fresh and kindly pock in each incision and bound it there for eight or ten days, after this time the patient was credibly informed. The patient would then develop a mild case [of smallpox], recover, and thereafter be immune."^[1]

This technique was documented as having a mortality rate of only one in a thousand. Two years after Kennedy's description appeared, March 1718, Dr. Charles Maitland successfully inoculated the five-year-old son of the British ambassador to the Turkish court under orders from his wife Lady Mary Wortley Montagu, who four years later introduced the practice to England.^[2]

[edit] Early Vaccination

In the early empirical days of vaccination, prior to Pasteur's work on establishing a germ theory and Lister's on antisepsis and asepsis there was considerable cross-infection. One of the early vaccinators is thought to have contaminated the Cowpox matter - the vaccine - with Smallpox matter (he worked in a Smallpox hospital) and this produced essentially variolation. Other vaccine material was not reliably derived from Cowpox, but from other skin eruptions of cows[1]. In modern times an effective scientific model and controlled production were important in reducing these causes of apparent failure or iatrogenic illness.

[edit] Eradication of smallpox

By 1977, smallpox, long considered to be the most deadly and persistent human pathogenic disease, was eradicated by the World Health Organization. This was accomplished through a massive, worldwide outbreak search and vaccination program. However, the variola virus that led to the death of 300 million in the 20th century alone was not completely exterminated with the disease it caused. Three known repositories of the virus were left, one in Birmingham, England which was later destroyed after an accidental escape from containment caused the death of Janet Parker, and two still remaining for possible anti-bio-weaponry research; at the Centers for Disease Control in Atlanta, Georgia and the State Research Center of Virology and Biotechnology in Koltsovo, Russia.

[edit] Use of vaccine currently

The vaccine consists of the virus which causes the related, yet far milder, cowpox disease; this virus is appropriately named vaccinia, from the Latin vaca which means cow. This vaccine has functional virus in it which improves its effectiveness but, unfortunately, causes serious complications for people with impaired immune systems (for example chemotherapy and AIDS patients, and people with eczema) and is not yet considered safe for pregnant women. A woman planning on conceiving within one month should not receive the smallpox immunization until after the pregnancy. In the event of an outbreak the woman should delay pregnancy if possible. A small, yet significant, percentage of healthy individuals also suffer adverse side-effects which, in rare cases, include permanent neurological damage. Vaccines that only contain attenuated vaccinia virus (an attenuated virus is one in which the pathogenicity has been decreased through serial passage) have been proposed but some researchers have questioned the possible effectiveness of such a vaccine. Others point out that mass vaccinations would probably not be needed to counter a bioterrorist attack if many millions of doses of the current (possibly improved) vaccine could be delivered to victims within several days of exposure (the vaccine is effective to that point). This, along with vaccinations of so-called first-responders, is the current plan of action being devised by the United States Department of Homeland Security and FEMA in the United States.

The vaccine can cause complications for those around those who are vaccinated. People who get the vaccine will shed virus particles through vesicles on their skin and possibly through their respiratory tract. Infections in close and not-so-close contacts can ensue. The current plan to vaccinate first responders has the potential to cause infection in the most vulnerable section of the population, the hospitalized ill. Family contacts are also susceptible, although they are less vulnerable because their immune systems are presumably intact. Secondary infection can cause skin disease, pulmonary disease and rarely, neurologic disease.

As of June 21, 2003, a scientific advisory panel had issued a recommendation against further vaccination of first responders because a significant number of those vaccinated suffered heart problems, notably pericarditis and myocarditis.

The main problem with developing a new, supposedly safer vaccine, is that, barring a bioterrorist attack on immunized individuals, its effectiveness cannot be tested on humans, and other animals do not naturally contract smallpox. Monkeys at USAMRIID research facilities have been infected, but tests on animals that are artificially infected with a human disease are notorious for giving false or misleading results. To demonstrate safety and effectiveness, human trials always have to confirm data obtained from animal testing.

The smallpox vaccine is also the only known treatment for monkeypox. As with smallpox, vaccination after infection is effective if the vaccine is given before symptoms develop.