Smallpox Vaccine: The Good, the Bad, and the Ugly

Abstract

Smallpox inarguably shaped the course of human history by killing countless millions in both the Old World and the New World.Dr. Edward Jenner's discovery of vaccination in the late 18th century, and the global eradication of smallpox in the 1970s, rank among the greatest achievements in human history.Amidst recent growing concerns about bioterrorism, smallpox vaccination has resurfaced from the history books to become a topic of major importance.Inoculation with vaccinia virus is highly effective for the prevention of smallpox infection, but it is associated with several known side effects that range from mild and self-limited to severe and life-threatening.As the United States moves forward with plans to vaccinate selected health care workers and the military, and perhaps offer the vaccination to all citizens in the future, it is important to fully understand and appreciate the history, risks, and benefits of smallpox vaccination. HISTORY OF SMALLPOX VACCINATION AND GLOBAL ERADICATIONSmallpox has been a scourge against humanity for at least the past 1500 years, and perhaps much longer than that.There is no mention of the disease in ancient Greek writings, but plagues of pustular disease in the Roman Empire bore a strong resemblance to smallpox.The literary record suggests that smallpox became established in the Mediterranean by the third century AD, and it was described in China around the same time.1 Smallpox subsequently changed the course of history and killed millions of people in both the New World and the Old World.Smallpox is caused by the variola virus, a DNA virus of the genus Orthopoxvirus.Humans are the only known reservoir for this virus.It is transmitted from person to person, and natural infection occurs by inhalation of respiratory droplets or contact with infected material on mucous membranes.Historical data suggest that smallpox is not highly transmissible, and high population densities are required to sustain transmission.Persons who have close, prolonged contact with an infected patient are at highest risk. 2 After a 10 to 14 day incubation period, the infected person develops severe symptoms with fever, malaise and headache.3 A maculopapular rash then develops with involvement of the face, mucous membranes, trunk and extremities.The lesions become pustular and deep over the subsequent 1 to 2 days, with scab formation by day 10.Patients are most infectious during the first week of the rash when viral shedding is greatest from ulcerated lesions in the oral mucosa.The overall mortality rate is about 30%, with most deaths occurring during the second week of illness.