Bioscope

          The New England Journal of Medicine issued an early release of articles on smallpox vaccinations and infections on December 19, 2002. These articles are available on the NEJM website (www.nejm.org) and the Journal issue containing these articles will be published in January, 2003.

Smallpox Vaccination -- The Call to Arms by T.L. Schraeder and E.W. Campion
A Model for a Smallpox-Vaccination Policy by S.A. Bozzette and Others
The Public and the Smallpox Threat by R.J. Blendon and Others
How Contagious Is Vaccinia? by K.A. Sepkowitz
A Different View of Smallpox and Vaccination by T. Mack
Letter to the Editor: A Smallpox False Alarm by J.A. Hanrahan, M. Jakubowycz, and B.R. Davis

          The main points in these articles are

• The public poorly understands smallpox and vaccinia, but this can be changed with education.
• A small percentage of immunocompetent people who are vaccinated will develop complications from vaccinia. A larger percentage of immunocompromised people will be affected.
• Secondary transmission of vaccinia (not smallpox) can occur even from healthy vaccinated people. This puts those with imperfect immune systems at risk even when they are not vaccinated. This risk is higher in hospital settings, perhaps as high as 11%, because hospitals have the highest number of susceptible patients.
• Models have been developed that predict that targeted vaccination of healthcare workers, before a smallpox attack is likely to save more lives than prior vaccination of the general population. There are many unproven assumptions in these models.
• A patient with a rash in a major hospital was eventually diagnosed with varicella-zoster virus (VZV), but it took just over 24 hours to eliminate smallpox as a possible diagnosis, even with CDC's help and during normal business hours.

          Taken together, it appears that we know quite a bit about smallpox and vaccinia, but not enough to predict what will happen. Most data on smallpox transmissions comes from older reports that are incomplete or more recent reports from developing countries, with developing health care infrastructures. Most data on secondary transmissions in hospitals comes from before 1950s, before chemotherapy for cancer, transplants, HIV, and corticosteroid treatments and therefore really applies to a different population than is in our hospitals today. The biggest risk from secondary transmission of vaccinia is to those in hospitals who are immunocompromised. Paradoxically, this risk will increase by vaccinating health care workers, who have more direct contact with that population. The health care workers need to be protected because they are the most likely to be exposed to smallpox in the event of an attack. The models are unconvincing.