BOSTON (Harvard School of Public Health) -- A new study by Harvard School of Public Health researchers suggests that if the threat of a bioterrorist attack using smallpox increases, Americans’ individual decisions about whether they will choose to be vaccinated will be heavily influenced by what they see practicing physicians choosing to do. If physicians are reluctant to be vaccinated themselves, large numbers of Americans will be unwilling to do it voluntarily. Also, if there are deaths from side effects of the vaccine, the public will be less willing to be vaccinated.

"Depending on events, many Americans may be cautious when deciding whether or not to take the smallpox vaccine," said Robert J. Blendon, professor of Health Policy and Political Analysis at the Harvard School of Public Health.

The study also shows that the majority of Americans hold a number of beliefs about smallpox and the smallpox vaccine that are incorrect, based on information from the Centers for Disease Control and Prevention (CDC). These misconceptions could lead some people to make inappropriate decisions about how they should respond to the threat of smallpox.

These findings, based on interviews with 1,006 Americans nationwide between October 8 and December 8, 2002, are published as part of an accelerated online release by the New England Journal of Medicine www.nejm.org making available a package of articles “to inform the current national debate about smallpox vaccination,” according to the journal. The articles will appear in the Jan. 30, 2003 print edition of NEJM. The Harvard study was funded by the Robert Wood Johnson Foundation.

The Vaccination Decision

Nearly two-thirds (65%) of Americans supported a policy of making the smallpox vaccine available to the general public now on a voluntary basis. Three in five Americans (61%) said they would take the smallpox vaccine or be re-vaccinated as a precaution against a bioterrorist attack using smallpox, if the vaccine were made available to them.

However, the survey showed that the actions of physicians significantly influenced the decision to be vaccinated. If people were told that their own physician and most other physicians were getting the smallpox vaccine, the proportion of the public willing to be vaccinated increased to 73 percent. However, if they heard that their own physician and many other physicians were refusing to take the vaccine, only 21 percent said they would be willing to get vaccinated.

Early cases of death resulting from smallpox vaccination are also likely to have a significant effect on Americans’ decision. Hearing that “some people” died from the smallpox vaccine decreased the proportion willing to be vaccinated to one in three (33%).

Public Knowledge and Beliefs about Smallpox and the Smallpox Vaccine

Many Americans hold a number of beliefs about smallpox and the smallpox vaccine that are incorrect, according to information provided by the CDC. (For more information about smallpox, go to the CDC website, www.bt.cdc.gov/agent/smallpox).

“It has been a long time since Americans have had experience with smallpox, and they do not know much about the disease,” said Professor Blendon. “This suggests the need for public education.”

The last case of smallpox was reported in the U.S. in 1949 and in the world in 1977. However, three in ten Americans (30%) believe there have been smallpox cases in the U.S. during the past five years, and 63% think there have been cases somewhere in the world during that time.

There is no known effective treatment for smallpox once someone contracts the disease. However, three-fourths of Americans (78%) believe that if someone came down with the disease, there is a medical treatment that would prevent them from dying or experiencing serious consequences.

A vaccine given within two or three days of exposure to smallpox will protect people against the virus. Only 42% of the public knows that this is the case.

Serious adverse reactions to the vaccine are expected to be relatively rare in patients without health conditions that contraindicate vaccination. But many Americans think it is likely that they would suffer serious side effects from the vaccine. One-fourth thinks they are very (6%) or somewhat likely (19%) to die and four in ten think they are very (11%) or somewhat likely (30%) to suffer serious illness from the smallpox vaccine.

In addition, government sources say that there are enough doses of the vaccine for everyone in the U.S. Only 16% of Americans believe that this is the case.