Effect Of Smallpox Vaccination Lasts Much Longer


A study found that the effect of smallpox vaccination lasts much longer than previously thought. In the age of bioterrorism Americans worry about what would happen in the case of an attack with smallpox. Due to concentrated efforts worldwide through the WHO for many years, smallpox could be declared eradicated in the US in 1949 and worldwide in 1972. American children since then did not receive a smallpox vaccination. However, 95% of Americans over the age of 35 have been vaccinated and according to a recent study have been shown to still have a very good immune response that likely would make them immune to a bioterrorism attack with smallpox virus.

Review article in the British Medical Journal 

A review article in the British Medical Journal (BMJ 2003;326:1164) on May 31, 2003 reports about a study by Oregon researchers from the Departments of Molecular Microbiology and Immunology in Portland. Dr. Mark Slifka and Dr. Erika Hammarlund (Oregon Health Sciences University) collected blood samples from 306 previously smallpox vaccinated volunteers to check for antibody levels as well as T cell responses against smallpox antigens. The volunteers were of different ages and included people who were vaccinated against smallpox as recently as last year and as long as 75 years ago. All of them showed a very good response due to high antibody levels and their serum was able to neutralize the smallpox vaccinia virus in Petri dishes.

Good T cell responses after 35 years of smallpox vaccination

The T cell mediated cellular immune response showed some slowing down in the older age group. However, another study done by a North Carolina research group and also presented at a meeting from the American Society for Microbiology in Washington, DC. and published recently (New England Journal of Medicine 2002;347:689-90) found that T cell responses lasted a very long time. A group of people vaccinated 35 years earlier, so the North Carolina group reported, had perfect T cell responses to the smallpox vaccinia virus. The conclusion of these studies is that the effect of smallpox vaccination lasts much longer.

Effect Of Smallpox Vaccination Lasts Much Longer

Effect Of Smallpox Vaccination Lasts Much Longer


There is no point of vaccinating more often than two times in a lifetime.  Even one-time vaccinated people often have good immunity against smallpox. People born after 1972 and never  vaccinated against smallpox should consider vaccination and discuss this with their doctors. There are, however, some known complications of the vaccine such as a myopericarditis (a heart condition). Next, generalized vaccinia can occur, a skin condition common in people with skin problems like acne or psoriasis. 1 in 10,000 immunizations will get viral encephalitis, which often leads to brain damage. There is presently a campaign to vaccinate 500,000 frontline healthcare workers in the US against smallpox. This is a government plan to prepare for a smallpox bioterrorism attack. Due to the possible complications so far only 35 000 healthcare workers have volunteered for vaccinations. Link to overview regarding history of smallpox from the CDC.

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