Childhood Vaccine May Protect Against Smallpox

Although many adults in the US and other countries received the smallpox vaccine as children, it is unclear if those shots would confer any protection in the event of a bioterrorism-related outbreak.

Some experts expect that people who were inoculated decades ago still might have at least partial immunity against smallpox, which would reduce the risk of catching the disease or at least lessen its severity.

In the US, the smallpox vaccine was required for school entry prior to 1972, and about 60% of the US population has been vaccinated.

The eradication of smallpox was officially declared in 1980, and according to the World Health Organization (WHO), national vaccination programs had stopped in all countries by the early 1980s, although the last reported case was in Somalia in 1977.

"We expect that there is some protection that continues," according to Dr. David Heymann, who heads the communicable diseases section of WHO in Geneva, Switzerland. However, he cautioned that it is nearly impossible to be certain of how well previously vaccinated people would be protected in the event of a smallpox outbreak.

The initial signs of smallpox infection include headache, vomiting and fever. Then pus-filled lesions form on the head and face, and may also appear on other parts of the body.

There is no treatment for the disease, which is fatal 20% to 40% of the time in unvaccinated people. However, if an individual has been exposed to the virus and is vaccinated within the next 4 days, it can reduce symptoms or prevent the disease.

In those who have been vaccinated years ago, however, the duration of immunity against the disease is uncertain, according to the WHO's Heymann. Vaccination provides "high rates of protection for at least 10 years," he said.

Officially, smallpox exists in only two laboratories -- one in the US and the other in Russia. However, there are some concerns that other governments or terrorist groups may have samples of the deadly virus.

Finding out whether a vaccinated person is still protected from smallpox is difficult due to the type of immunity caused by the vaccine. It is possible to gauge immunity induced by many types of vaccines by measuring levels of antibodies to an infectious agent.

But the absence of antibodies to smallpox on a blood test does not mean that there is not some lingering immunity to the virus, since a person could still have a type of immunity called cellular immunity. Even in the absence of antibodies, cells may be sensitized to smallpox and capable of triggering a protective reaction when exposed to the virus.

Evaluating a person's immunity against smallpox is difficult. In the past, a process called "rechallenging" was the only way to know for sure that a person was still protected.

Smallpox vaccination causes a small lesion to form at the site of the inoculation. When a vaccinated person was "challenged" with a second dose of vaccine in another location and did not develop the tell-tale scar, then that person was thought to be immune to the virus. The formation of a second lesion indicated a lack of immunity.

Despite the inability to measure immunity with any accuracy without rechallenging the vaccinated, previous studies of people exposed to natural smallpox after being vaccinated suggest that some protection against the disease may linger for decades.

In a 1972 study, researchers analyzed 680 cases of smallpox that were imported from other regions into Europe and Canada from 1950 to 1971. About half of unvaccinated people who were exposed to the virus died from the disease. But as would have been expected, less than 2% of those who had been vaccinated within the previous 10 years died.
But vaccination still reduced the risk of death 20 years after the fact among people aged 10 to 49. The results show that past vaccination leads to a "significant decrease in mortality rate and severity of disease.

About half of the unvaccinated died compared with about 4% of those who had been inoculated 20 years earlier.

A study, published in 1913, found that people who had been vaccinated against smallpox as children were much less likely to die during an outbreak of the disease in Liverpool, England, from 1902 to 1903. What this study tells you is that there is indeed long-lived immunity.

Although the protection of the vaccine waned with age, among people older than 50, only about 5% of people who had been vaccinated as a child died compared with about 50% of unvaccinated people.

The public needs to be reassured that if you were vaccinated as a child, you might have some immunity.

A spokesperson for the CDC told Reuters Health that it would be "uncertain" whether people who had been vaccinated in the past were still immune to smallpox, and it would be "fair to assume" that they would need another vaccination to guarantee immunity.

The threat of bioterrorism has spurred the US government to build up a stockpile of smallpox vaccine to have on hand in case of an outbreak of the often fatal disease.

The supply of 300 million doses of vaccine -- enough to inoculate every one in the country -- will be ready by next year. However, there are no plans to reinstate a mass vaccination program, since the proven risk of serious and even fatal side effects of the vaccine outweigh the potential risk of bioterrorism.

Historically, the smallpox vaccine caused serious reactions in about 1 in every 4,000 persons and death in about 4 per 1 million.

DR. MERCOLA'S COMMENT:

The clear take home message here is that if you are part of the majority of the US population that has been vaccinated then it is highly likely that you are protected against smallpox.

As the information above states, 50% of people dying from smallpox exposure is quite a dramatic difference compared to 4% of those who had received immunizations at least 20 years ago. Those type of odds seem quite good and impressive.

Even if you had a blood test that did not show an antibody present that is not necessarily an indication that you do not have protection. Cellular immunity, rather than the humoral immunity that an antibody measures, may still be present and provide more than an adequate protective response.

It is important to remember here that during earlier smallpox epidemics that not everyone died or acquired the disease. This was likely due to the fact these individuals were leading healthy lifestyles that allowed their immune system to defeat the infection through their own natural immunity.

The key to enhancing your immune system is to clean up your diet by following an optimized eating plan.

It appears likely that there will be some US laws implemented next year allowing the government to force anyone to get a smallpox vaccine.

I will be pushing very strongly for modification of this upcoming law to have a provision for testing natural immunity prior to a full blow dose of smallpox vaccine.

As the article states above, one can functionally test someone by giving them a challenge dose of the vaccine and observing if they form a response.

Related Articles:

U.S. Officials Want a Dose for Every Person in the Country by the End of 2002

Among Biological Weapons, Smallpox is in a Class by Itself

Sanitation V. Vaccination - The Origin of Smallpox

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