Implementing a Smallpox Vaccination Program Aboard an Aircraft Carrier

Military Medicine, Jun 2004 by Apple, Jeff, Hare, Patrick, Crerar, Chris, Walker, Errika, Et al

Objective: To determine the feasibility of implementing a smallpox vaccination program aboard an aircraft carrier in conjunction with anthrax vaccination. Methods: Retrospective review of smallpox vaccination program conducted from January 17, 2003 to February 19, 2003. Morbidity and loss of manpower were the major endpoints. Results: There were 5,204 sailors available for vaccination. There were 243 (4.7%) medical exemptions and 24 administrative exemptions. During the program, 4,931 sailors were vaccinated. There were five reportable complications. Three sailors had autoinoculation, one sailor had localized cellulitis, and one patient had a positive [beta] human chorionic gonadotropin during vaccination. None of the complications required medical evacuation. Only two sailors required time off from duty. Conclusions: Smallpox vaccination can be accomplished rapidly and safely aboard an aircraft carrier. There was not an increase in adverse events compared to historical data despite the close-quarter conditions. Smallpox and anthrax vaccinations can be completed simultaneously with minimal morbidity.

Introduction

On December 13, 2002, the President of the United States implemented a nationwide smallpox vaccination program in response to events occurring in September and October 2001.1 Although smallpox was declared eradicated from the earth in 1980 by the World Health Organization, stores of the virus that cause smallpox, variola, remain.2 The President's directive reflected the threat to troops stationed abroad and at sea from bioterrorism. To our knowledge, there has never been a smallpox vaccination program initiated and completed on an aircraft carrier. Although we had recent experience with anthrax vaccination, the risks posed by a live-virus vaccine, including autoinoculation and contact transmission, were obvious. This report is an account of our planning and implementation of a smallpox vaccination program, with particular emphasis on the actual vaccination schedule and major adverse events. Lessons learned on wound care and adverse event prevention are discussed.

Background

It is speculated that smallpox began around 10,000 BC with the first agricultural settlements. Written descriptions of the disease first appeared in 4th century AD China and by the 16th centuiy, smallpox had spread to the Western Hemisphere, where it decimated American Indian tribes such as the Aztecs and Incas.3 Humans are the only known reservoir, with transmission usually accomplished by direct face-to-face contact. Infection caused by indirect contact, through blankets and other fomites, is rare.

Vaccination programs began in India around 1000 AD. At that time, material from smallpox scabs was inoculated into skin or nasal passages. It was noted that the ensuing infection was less severe than primary smallpox infection and conferred immunity against further attacks. This process of using pustular or scab material was called variolation. In 1796, Edward Jenner was credited with developing the process we know today as vaccination.4 Using cowpox virus, material was injected into the skin of individuals and it conferred smallpox immunity. Cowpox and vaccinia virus are members of the Orthapoxuirus genus, Poxviridae family. Immunity is conferred to all members of the family, including variola, which causes smallpox. Vaccinia eventually became the primary virus used for smallpox vaccination. It was grown and harvested from calf flanks, creating a more readily available supply of vaccine. Methods for developing a stable, long-lasting vaccine were started in the 1940s and were perfected by Collier.3 Routine vaccination was stopped in the United States in 1971, except for certain medical personnel and the military. Military personnel stopped receiving the vaccination in 1990, although some branches stopped sooner. As of 1985, there were only two stockpiles of variola virus: one in the USSR and one in the United States. There is concern today that stockpiles of variola might exist outside these locations and may be used as a weapon of bioterrorism.

The symptoms of smallpox vary depending on the stage of infection. In the first stage, which usually begins anywhere from 7 to 17 days after exposure, the patient experiences fever, malaise, and headache. A maculopapular rash appears soon afterward. This rash develops into the classic papulovesicular rash, which scabs over after about 1 week.5 The rash has a typical spread from the face, oral cavity, and forearms to the trunk and legs. This is known as centrifugal spread. all of the lesions are usually in the same stage of development, in contrast to varicella, which causes chickenpox. Once the scabs fall off in 3 to 4 weeks, the patient is no longer infectious. The greatest risk of spread comes when the lesions in the oral cavity ulcerate, causing a large load of virus to be concentrated in the saliva. This usually occurs when the rash first appears. This can then be spread to other persons through coughing and direct face-to-face contact.