Which pox is it?

February 2002

---Philip A. Brunell, MD

An article recently appeared in the local newspaper entitled “Some want smallpox shots now.” The article described the clamor for smallpox vaccine. A parent group in Maryland has been organized to “pressure federal officials for the vaccine” and a U.S. senator “wants his four granddaughters to be inoculated,” the article stated.

I was bemused by this as I recalled what parents used to go through to avoid having their children receive smallpox vaccine. It reminded me of the last case of smallpox to pass through the United States.

In the 1960s, a teenager from Brazil was traveling with his missionary family to Toronto. On the flight from Brazil to New York City, he became febrile. The family took a cab from JFK Airport (then called Idlewild) to Grand Central Station where the family sat in an open waiting room awaiting their train to Toronto. It is unclear whether he started to erupt at this time or after the family boarded the train for their half-day trip to Toronto.

This child touched his inoculation site and inoculated his lower lid with vaccinia virus. Source: Philip A. Brunell, MD

When he arrived in Toronto, he clearly had an eruption and was seen by several physicians, each diagnosing him as having chickenpox. Finally, a diagnosis of alastrim or variola minor was made. By this time, he had obviously exposed a lot of people. Fortunately, there were no secondary cases.

At this time, vaccination was required for entry into the United States. On questioning, the parents admitted they had convinced the child’s physician to issue a certificate of immunization without having actually immunized the boy.

This was not uncommon in those days as this vaccine, which is not unlike the one we would use today, produced many adverse events. In those days, although the risk of smallpox was probably greater than it is today, many parents did not want their children immunized.

In this instance, the fear was strong enough to have a clergyman’s child enter the United States with a falsified immunization record.

For those of us who were around in the days of smallpox vaccine, it was not difficult to understand parental fears. As is true of most vaccines, common reactions were generally not as severe as rare ones. One of the most troublesome and common adverse events was the scar of the vaccination itself, which prompted parents to urge that little girls be immunized in less visible places, eg, the buttocks. This was before bikinis were popular.

Unfortunately, vaccination in the highly contaminated diaper area not infrequently led to bacterial superinfection. Occasionally, properly placed vaccine sites also would become infected. Keeping little ones from getting their hands into vaccination sites was difficult, and autoinoculation (1:1200) was sometimes seen (figure 1a and 1b). Generalized vaccinia (1:2500), ie, the presence of a few disseminated lesions occurred but these were usually without significance. Erythema multiforme was another reaction to vaccination (figure 2).

Serious adverse events

More serious reactions to vaccination were, fortunately, less common but accounted for most of the fatalities, which were estimated to occur once in 1 million vaccinations. Vaccinia necrosum (figure 3) occurred in 1.5 per 1 million vaccinations and was facetiously referred to by immunologists as a screening test for congenital cellular immune deficiencies.

This often had a fatal outcome and was also seen in patients with acquired cellular immune defects (figure 4). Encephalitis following immunization occurred in about 1:80,000-100,000 cases and during the New York vaccination program in the 1940s there was a 4% mortality rate. Eczema vaccinatum (1:25,000) sometimes was fatal.

Not only were the vaccinees at risk but also their contacts. Vaccination was contraindicated in families with individuals at high risk of complications. Vaccinia remained viable in the vaccination crust often for weeks following vaccination. Vaccinia virus could be isolated from sweeping of hospital rooms months after a child with a recent vaccination was in the room. Therefore, certain rooms in our hospital where patients with recent vaccinations were kept would be barred from patients with eczema who required hospitalization.

Secondary cases

The Brazilian child raises a number of issues, one of which is why were there no were no secondary cases? At that time we had a population that was well protected against smallpox, as there was universal vaccination in the United States and Canada. How well those who were immunized are still protected is unclear. At this time, there are several subsequent generations of younger people who have not been vaccinated. It generally is accepted that variola minor or alastrim is less contagious than variola major. It is unclear at what point the Brazilian child actually was contagious, as patients with smallpox are believed to be most infectious soon after onset of rash.

Alastrim is a much milder disease than variola major infection and can more easily be mistaken for chickenpox (figures 5, 6 and 7). Even in the times when there was an awareness of these diseases, this was a problem. At the time this child arrived in Canada, it was probably furthest from the minds of the attending physicians. Therefore, it is important that our awareness of smallpox be increased if we are to detect cases of smallpox.

Differential diagnosis, particularly of atypical forms may be difficult. It is essential that diagnosis be made early to contain the spread of the disease. Thus, it is important that one be suspicious and be familiar with the clinical features of smallpox and the atypical forms, eg, the hemorrhagic form, both of this disease and of chickenpox. This can be found on a number of Web sites, including the CDC site. It also is important to take appropriate precautions, to isolate suspected patients and to obtain and transport appropriate specimens for diagnosis. It is apparent that a false alarm will set a lot of things in motion that will have its cost in dollars, morbidity from vaccination and inconvenience. However, missing a case of smallpox will be even more devastating.

The risk of vaccination is clear to those of us who were around at the time when it was routine. There was a risk to the vaccinees and to contacts. Weighing these risks against the possibility of getting smallpox, Henry Kempe stood up at a meeting of what we now call the Pediatric Academic Societies before the global eradication of smallpox and declared he would not immunize another American child. At the present time, we must reevaluate these risks.