The next measles epidemic and individual rights

November 2002

---Philip A. Brunell, MD

Every year I am trotted out to speak on measles at a course for professionals on the NIH campus given by the FDA. It is assumed that consistent with my vintage must come some wisdom concerning measles. Only two people in the room had seen a case and they were closer to my age than the rest of the group. I love to use the epidemic of measles which occurred in Corpus Christi, Texas in 1985 as a case study in the course. At that time, I was working in San Antonio, and I had the good fortune to meet Tracy Gustafson, who was a bright-eyed bushy-tailed epidemiologist working at the state health department. The Corpus Christi outbreak occurred just a few years prior to the larger epidemic of measles, which swept the United States affecting about 50,000 people and leaving more than 100 dead.

During the ‘80s, there had been a number of Texas school outbreaks despite the fact that immunization was required as a condition of attendance and more than 95% of the students in the affected schools had records of receipt of measles vaccine. Tracy wanted to find out what percentage of immunized students was necessary to prevent an epidemic. He proposed that at the first case of measles in a Texas school, he would obtain blood samples on every child whose parents would provide consent (57% or 1,806 students in Corpus Christi). At the same time all unimmunized contacts of measles cases were urged to be vaccinated.

The first case occurred in a student on April 26, 1985, but she did not visit a physician until four days later. The physician was astute enough to suspect the diagnosis and sent a blood sample for testing which, after several days, was reported positive for measles IgM, by which time two additional cases were diagnosed. All told there were 157 cases reported with 0.3% and 1.8% of the students in the two study schools selected. In another school in Corpus Christi not included in our study, 3% of the students got measles. The epidemic started in the schools and then spread to younger children (N Engl J Med. 1987;316:771).

Their records indicated that more than 99% of the students had been appropriately immunized, which at that time was a single dose of live vaccine after the first birthday.

Despite the fact that 73 of 74 vaccinees had documentation of prior measles immunization in the school record, they were found to be seronegative. In all, 4.1% of the students in the schools were seronegative, 4.5% (70 of 1,572) and 1.4% (three of 213) (P=0.06) whose school records indicated that they had received one or two doses, respectively. These children had either failed to respond to a single dose or their records were faulty. A few years earlier we had studied 300 children in neighboring San Antonio and found that only 1.7% of children who had received a single dose of measles-mumps-rubella vaccine (MMR, M-M-R II, Merck) at 33 different providers in the community were seronegative. If this were the true rate of vaccine failure after a single dose of measles-containing vaccine, there would be an accumulation of 68,000 susceptibles annually.

A few years later we were to experience the first large measles epidemic in the United States in more than a decade. It was apparent that the one-dose measles policy would still leave enough susceptibles to sustain substantial epidemics of measles. Subsequently a two-dose measles vaccine recommendation was implemented. There were other lessons to be learned from the epidemic of 1988-90. It was apparent that although the national rates of immunization looked great there were populations that had a low rate of immunization, concentrated in the inner cities. Efforts have been made to address this problem. For the past few years the program of measles elimination has resulted in fewer than 100 cases of measles annually in the United States, all of them imported with no spread to contacts. Prior to this, there was an outbreak of measles in Anchorage, Alaska, where despite a two-dose requirement there were enough susceptibles in the school to sustain an epidemic.

Why do I think there will be another epidemic? With a two-dose measles requirement, if we had a vaccine failure rate of 1.4%, there would be an accumulation of 56,000 susceptibles annually spread over the United States. However, if one adds to it the number of children not receiving vaccine because of philosophical or religious objections, which in Colorado was reported to be 1.8% and 0.2% of all children respectively (JAMA. 2000;284:3145-3150) or in Oregon where the rate of philosophical exemptions in 2001 was said to be 2.7%, we now approach the number of susceptible children needed to support an epidemic of measles in schools in Corpus Christi.

But, if no one else has measles, isn’t my child safe? Colorado is a wonderful state that attracts visitors worldwide and those who need a place to invest in vacation places as well as those who just like to ski. Migrant workers appear to be less of a problem than in the past because of the successful measles immunization program throughout Latin America. Remember that our last cases of wild polio in the United States afflicted a group who did not believe in immunization; it was imported by one of their members. One of the most devastating college outbreaks of measles was at Principia College in Illinois, which is sponsored by a religious group that eschews vaccination. In 1985 there were 128 cases and three deaths at the college (MMWR. 1985;34[10]:129). Unfortunately, the group that will suffer the most in a measles epidemic are not those whose choose not to have them immunized but those who are too young to receive vaccine. Measles is most severe in the very young and not much fun for anyone.

It is difficult to argue about the individual’s freedom as opposed to responsibility to their own children and to the rest of the community. One of the points that seems to be glossed over in the current debate over the use of smallpox vaccine is the responsibility for not infecting contacts with the vaccine. This certainly happens and there are many in this country who would be injured as a result of someone else being vaccinated. Think of the person who empties the trashcan of the dressing from a smallpox vaccination. It is of interest that there has been an ongoing epidemic of pertussis in Boulder, Colo., which has a high rate of objectors to vaccination. This has spread to the neighboring communities (Atlantic Monthly. Sept 2002). After pertussis, can measles be far behind?