Sonja S. Hutchins

Epidemiology of measles in the United States in 1989 and 1990

During 1989 and 1990 measles incidence increased sharply in the United States. We compared cases reported during these years with those reported between 1981 and 1988. Incidence increased 462% in 1989, and incidence in 1990 (11.2/100,000) was the highest in more than a decade. Although all ages were affected the greatest increases were in children < 5 years and in adults. Incidence was 7- to 10-fold higher among racial/ethnic minority preschoolers than whites, and 80% of vaccine-eligible preschool age cases were unvaccinated. Complications occurred in 9418 (20.5%) cases, most frequently in young children and adults. Large urban outbreaks affecting predominantly unvaccinated preschoolers were common; 47% of all cases reported in 1990 were associated with 5 outbreaks. Reasons for the increased incidence are not clear. Current information suggests no change in vaccination coverage among preschool age children or in vaccine efficacy. Continued surveillance and evaluation of epidemiologic and laboratory data are necessary. The most pressing need is to improve age-appropriate vaccination among preschool age children.

Protection of racial/ethnic minority populations during an influenza pandemic

Racial/ethnic minority populations experience worse health outcomes than do other groups during and after disasters. Evidence for a differential impact from pandemic influenza includes both higher rates of underlying health conditions in minority populations, increasing their risk of influenza-related complications, and larger socioeconomic (e.g., access to health care), cultural, educational, and linguistic barriers to adoption of pandemic interventions. Implementation of pandemic interventions could be optimized by (1) culturally competent preparedness and response that address specific needs of racial/ethnic minority populations, (2) improvements in public health and community health safety net systems, (3) social policies that minimize economic burdens and improve compliance with isolation and quarantine, and (4) relevant, practical, and culturally and linguistically tailored communications.

Measles outbreaks in the United States, 1987 through 1990

BACKGROUND During 1989 and 1990 reported measles cases in the United States increased 6- to 9-fold over the annual mean of 3000 between 1985 and 1988. To evaluate recent epidemiology we summarized measles outbreaks. METHODS Confirmed measles cases reported to the National Notifiable Disease Surveillance System during 1987 through 1990 were analyzed. An outbreak was defined as > or = 5 epidemiologically linked cases. RESULTS There were 815 outbreaks, accounting for 94% of the 52,846 cases reported. Similar to 1985 and 1986, 3 patterns of measles transmission during outbreaks were identified: (1) predominantly among unvaccinated pre-school age children < 5 years of age (38% of outbreaks); (2) predominantly among vaccinated school age children 5 to 17 years of age (40%); and (3) predominantly among unvaccinated and vaccinated post-school age persons > or = 18 years of age (22%). Most outbreaks were small (median, 12 cases), but very large outbreaks occurred (maximum size, 10,670). Although school age outbreaks (58%) predominated during 1987 and 1988, preschool age (40%) and post-school age (23%) outbreaks were more important during 1989 and 1990. CONCLUSIONS Recent epidemiology suggests that to achieve elimination of measles, ACIP recommendations must be fully implemented, including (1) routine administration of the first dose of measles vaccine from 12 to 15 months of age and (2) use of a routine two-dose schedule to prevent school age and post-school age outbreaks.

Evaluation of the Measles Clinical Case Definition

An accurate system of identifying and classifying suspected measles cases is critical for the measles surveillance system in the United States. To examine the performance of the clinical case definition in predicting laboratory confirmation of suspected cases of measles, we reviewed 4 studies conducted between 1981 and 1994. A clinical case definition was examined that included a generalized maculopapular rash, fever (>or=38.3 degrees C, if measured), and either a cough, coryza, or conjunctivitis. Serological confirmation of measles was done either by hemagglutination inhibition assay, complement fixation assay, or enzyme immunoassays. The positive predictive value of the clinical case definition decreased from 74% to 1% as incidence decreased from 171 cases/100000 population to 1.3 cases/100000 population. Sensitivity was high, and for the larger studies with the most precise estimates, sensitivity was 76%-88%. The low positive predictive value of the clinical case definition in settings of low incidence demonstrates that serological confirmation is essential to ensure an accurate diagnosis of measles when measles is rare.

Effectiveness and cost-effectiveness of linking the special supplemental program for women, infants, and children (WIC) and immunization activities.

Objective: To raise immunization coverage among children at risk for underimmunization, we evaluated the effectiveness and cost-effectiveness of immunization activities in the Special Supplemental Program for Women, Infants and Children (WIC).Method: A controlled intervention trial was conducted in seven WIC sites in Chicago between October 1990 and March 1994. At intervention sites, staff screened children for vaccination status at every visit, referred vaccine-eligible children to either an on-site WIC nurse, on-site clinic, or off-site community provider, and issued either a 3-month supply of food vouchers to up-to-date children or a 1-month supply to children not up-to-date—a usual practice for high-risk WIC children. Our primary measure of effectiveness was the change in the baseline percentage of up-to-date children at the second birthday; cost-effectiveness was approximated for each of the three referral interventions.Results: After one year, up-to-date vaccination coverage increased 23 % above baseline for intervention groups and decreased 9% in the control group. After the second year, up-to-date vaccination further increased to 38 % above baseline in intervention groups and did not change in the control group. The total cost per additional up-to-date child ranged from

Preschool children at high risk for measles: opportunities to vaccinate.

30 for sites referring children off-site to

Persistence of Vaccine-Induced Antibody to Measles 26–33 Years after Vaccination

73 for sites referring children on-site to a nurse.Conclusion: This controlled intervention trial of screening, referral, and a voucher incentive in the WIC program demonstrated a substantial increase in immunization coverage at a low cost. Continuing to design linkages between WIC and immunization programs by building on WICs access to at-risk populations is worth the investment.

Protecting Vulnerable Populations From Pandemic Influenza in the United States: A Strategic Imperative

OBJECTIVES In 1989 and 1990 the United States experienced a measles epidemic with more than 18,000 and 27,000 reported cases, respectively. Nearly half of all persons with measles were unvaccinated preschool children under 5 years of age. We sought to identify potential sites for vaccine delivery. METHODS Preschool children with measles were surveyed in five inner cities with measles outbreaks in 1989 to 1990 to assess the childrens use of health care services and federal assistance programs before contracting measles. RESULTS Of 972 case children surveyed, 618 (64%) were eligible for measles vaccination at measles onset. Of those, 93% had previously visited a health care provider (private physician, public clinic, hospital emergency department, or hospital outpatient department) and 65% were enrolled in a federal assistance program (AFDC, WIC, or food stamps). Based on parent-reported reasons for health care visits, in Dallas and New York City, health care providers of 24% of 172 children may have missed at least one opportunity to administer measles vaccine. CONCLUSIONS Many potential opportunities exist to raise the vaccination coverage of unvaccinated preschool children. These opportunities depend on (1) health care providers taking advantage of all opportunities to vaccinate, and (2) immunization services being linked to federal assistance programs.

Vaccination Levels Associated with Lack of Measles Transmission among Preschool-Aged Populations in the United States, 1989–1991

Because measles-specific antibody titer after vaccination is lower than after natural infection, there is concern that vaccinated persons may gradually lose protection from measles. To examine the persistence of vaccine-induced antibody, participants of a vaccine study in 1971, with documentation of antibody 1-7 years after vaccination, were followed up in 1997-1999 to determine the presence and titer of measles antibody. Of the 56 participants (77% were 2-dose recipients), all had antibodies detected by the plaque reduction neutralization (PRN) antibody assay an average of 26-33 years after the first or second dose of measles vaccine; 92% had a PRN titer considered protective (>1 : 120). Baseline hemagglutination inhibition antibody titer in 1971 strongly predicted follow-up PRN antibody titer (P<.001). Persistence of antibody in these primarily 2-dose recipients supports the current elimination strategy to achieve and sustain high population immunity with a 2-dose schedule.

Population Immunity to Measles in the United States, 1999

Protecting vulnerable populations from pandemic influenza is a strategic imperative. The US national strategy for pandemic influenza preparedness and response assigns roles to governments, businesses, civic and community-based organizations, individuals, and families. Because influenza is highly contagious, inadequate preparedness or untimely response in vulnerable populations increases the risk of infection for the general population. Recent public health emergencies have reinforced the importance of preparedness and the challenges of effective response among vulnerable populations. We explore definitions and determinants of vulnerable, at-risk, and special populations and highlight approaches for ensuring that pandemic influenza preparedness includes these populations and enables them to respond appropriately. We also provide an overview of population-specific and cross-cutting articles in this theme issue on influenza preparedness for vulnerable populations.