In the age of threats about bioterrorism many 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 were no longer vaccinated. 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. A recent 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. 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 is longlasting.
There is no point of vaccinating more often than two times in a lifetime and even one-time vaccinated people often have good immunity. People who are born after 1972 and who have never been vaccinated against smallpox would be well advised to consider vaccination and discuss this with their doctors. There are, however, some known complications of the vaccine such as a myopericarditis (a heart condition) , generalized vaccinia (a skin condition common in people with skin problems like acne or psoriasis), and 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 to be prepared for a smallpox bioterrorism attack. Due to the possible complications so far only 35 000 healthcare workers have volunteered for vaccinations. Link to overview of smallpox from the CDC: https://emergency.cdc.gov/agent/smallpox/overview/disease-facts.asp
Last edited December 9, 2012