Before widespread immunization, rubeola (measles) was the most communicable disease of childhood, and most women of reproductive age had high levels of immunity following natural infection. This resulted in a low incidence of rubeola during pregnancy (from 0.4 to 0.6 cases per 10,000 pregnancies). However, those women who contracted rubeola during pregnancy had high rates of premature labor, spontaneous abortion, maternal complications and even mortality as a result of disease. An increasing number of adult rubeola cases have recently been reported. In 1994, 48.8 percent of the rubeola cases reported occurred in persons from 15 to 39 years of age. Neubert and colleagues conducted a cross-sectional study to measure antibodies to the rubeola virus in women presenting for prenatal care to estimate the need for preventive measures such as postpartum vaccination.

Women included in the study presented for care at urban or suburban medical facilities, either resident-supervised clinics or private practices. Blood samples were collected from 768 women presenting between December 1992 and August 1994. The mean age of the women studied was 26.4 years, and the mean gravidity was 2.6. A seronegative result was defined as a hemagglutination test titer of 1:8 or less (i.e., Measelisa IgG value of 0.13 or less). Using these criteria, 75 women (9.8 percent) were seronegative. Women who were seronegative tended to be younger than those with immunity, but no significant relationship could be demonstrated between sero-negativity and gravidity or parity.

The percentage of women who were non-immune for rubeola was highest in those who described their race as “other” (13 percent), followed by white (12.4 percent) and black (4.3 percent). Women at the suburban sites were significantly more likely to be nonimmune than those who presented at the inner-city sites. The rate of seronegativity in suburban women attending the resident clinic was 20.5 percent, compared with 9.2 percent of the suburban private practice patients, 8.2 percent of inner-city patients seen in private practice settings and 3.2 percent of inner-city patients attending resident-supervised clinics. Many of the women who presented at the suburban resident-managed clinics were Hispanic and may have had decreased access to vaccination because of recent immigration or lack of contact with traditional public health services.

The authors conclude that an appreciable number of women presenting for prenatal care may lack antibodies to the rubeola virus. They attribute the low rates of seronegativity in inner-city women to public health campaigns targeting minority groups. The authors call for greater vigilance in ascertaining the rubeola immune status of women of childbearing age and the identification of patients who should receive the combined measles, mumps and rubella vaccine in the postpartum period.

editor's note: The authors of this study are concerned about complacency deriving from the low incidence of rubeola currently reported in the United States. They found that overall, approximately 10 percent of pregnant women were vulnerable to measles, and in one subgroup, one fifth of all pregnant women were at risk. Measles is one of the most infectious diseases known, and outbreaks have occurred when only 3 to 7 percent of the population was at risk. The number of adults at risk for measles in the United States appears to be steadily increasing because immunization was either missed or was ineffective, and natural infection (which stimulates immunity) has been absent for many years. The measles epidemic scenario has already been played out in West Africa, where a measles epidemic disproportionately affected young adults, particularly pregnant women, with serious and often fatal results for mothers and neonates. Perhaps it is time for pilot studies to measure the prevalence of seronegativity to rubeola in representative U.S. adult populations. This information could contribute to rational strategies to prevent outbreaks of measles. Measles, particularly in adults, is not a benign disease. The stakes for prevention are now higher than they were before the introduction of childhood immunization: it would be tragic if the long-term consequences of immunization were to displace the impact of the disease to the adult and neonatal populations.—a.d.w.