The Record (Bergen County, NJ)

Weighing the risks of a vaccine for smallpox

by Howard Fienberg
July 30, 2002

CURRENT STRATEGIES to react to an outbreak of smallpox in the United States could lead to as many as 110,000 deaths, according to a new study in the Proceedings of the National Academy of Sciences. Noting that vaccination of the entire American population would save the most lives, the study seems at odds with the federal Advisory Committee on Immunization Practices recommendation that only critical emergency personnel be given the vaccine.

Should the vaccine now be offered to the general public?

Smallpox spreads fast (by inhalation or contact) and is deadly (at least 30 percent of unvaccinated victims die), and most experts believe that immunity has waned among people who were vaccinated before smallpox was thought to be eradicated in the 1970's. Even if the decision were made to vaccinate the entire population right now, do we have enough of the stuff? The federal government has about 15 million doses in storage, which can be diluted into 75 million (without any loss in effectiveness).

Drug maker Aventis Pasteur recently donated its frozen stockpile of 80 million doses. The federal government is also purchasing 220 million doses made with an experimental technique, which would bring the stock of vaccine up to 300 million doses by the end of the year.

As the smallpox vaccine has some nasty side-effects, vaccinating the entire population would not be painless. Approximately 1 out of every 150,000 people would contract severe, debilitating infections and another 1 in 500,000 people would die from the vaccine. So, if all 280 million Americans were vaccinated, more than 500 would almost certainly die. Suddenly, mass vaccination looks less appealing.

The Centers for Disease Control and Prevention is thus against pre-exposure vaccination, preferring to wait until after exposure is confirmed to treat the victims and anyone who may have come into contact with them. This is know as "ring containment," but is it a viable strategy? Once contracted, smallpox incubates 10-12 days, leaving its victims feverish and nauseous. Though the symptoms abate, the victim is now infectious and will not develop the tell-tale rash for another two to four days.

At this point, there is no "cure" for smallpox. The vaccine works well pre-exposure, but evidence of post-exposure efficacy is only anecdotal. That anecdotal evidence points to the vaccine only working if the victim is inoculated within four days of contact with smallpox.

The crucial question in this scenario is: Can we respond to a smallpox outbreak?

While the CDC believes it can win the race against time, many outside of the institution disagree. Dr. Richard Levinson of the American Public Health Association answers the question, "unequivocally, no." He cites the example of the West Nile Virus, which paralyzed the CDC and the whole of New York City's public health infrastructure.

Dr. William J. Bicknell of Boston University's School of Public Health thinks it would be "virtually impossible" for public health officials to react within the necessary window of time. The ring containment strategy, which was used successfully to eradicate smallpox, works well when there are only a few cases of the disease in a mostly vaccinated population. But for a mobile populace with little or no immunity, the strategy seems wishful thinking.

In our risk-averse society, it is not clear how people would react to a drug with such side-effects when the threat is not staring them in the face. Levinson worries that with limited public interest and information (fewer than 200 people turned out for the first two of the CDC's public forums), there could be a reverse backlash against the vaccine. However, making the vaccine available along with a strong public information effort on the risk of smallpox, as well as the risks inherent in the vaccine, should work.

While Levinson expects 300-600 deaths from the vaccine in a worst-case scenario, that could be significantly cut by not vaccinating the most vulnerable groups: children and the immuno-compromised (i.e. HIV/AIDS sufferers and chemotherapy patients).

Science shows this to be one of the best options. It is time to give Americans a choice.

Howard Fienberg is senior analyst with the Statistical Assessment Service, a nonprofit, nonpartisan research organization in Washington, D.C.

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