PUBLIC HEALTH BRIEFS
confirms the observations of many others.5 6 Second, an active EHS was a suitable location for establishing a rubella screening and immunization program. The screening was easily incorporated into the routine pre-employment health examination. Most importantly, we have been reasonably successful in vaccinating the susceptible women in our program. In post-pubescent rubella vaccine campaigns, both pregnancy and vaccine reactions are of concern. Pregnancy was infrequent in our study population. Overall, in the United States, pregnant workers comprise 8.8 per cent of the ".ever-married women" of reproductive age currently employed.7 Thus a program which is based in the work force could provide an acceptable area for rubella screening and vaccination programs. Side reactions were not a problem in our study population. Those individuals with complaints serious enough to report to EHS for medical attention had conditions unrelated to rubella immunization. A study to follow both an immunized and a control group for concurrent symptoms would be a useful contribution. Our experience demonstrates that a rubella screening and immunization program for women employees, which includes an informed consent and discussion period, successfully captures an "at-risk" population and provides continuing health education.
REFERENCES 1. Judson FN, Shaw BS and Vernon TM: Mandatory premarital rubella serologic testing in Colorado: A preliminary report. JAMA 729:1200-1202, 1974. 2. Fox JP, Rainey HS, Hall CE, et al: Rubella vaccine in postpubertal women: Experience in western Washington state. JAMA 236:837-843, 1976. 3. New York State Public Health Law 2803; Section 720.6. 4. Center for Disease Control. A Procedural Guide to the Performance of the Standardized Rubella Hemagglutination-Inhibition Test. U.S. Department of Health, Education, and Welfare, Mental Services and Mental Health Administration. Center for Disease Control, Atlanta, GA, October 1970. 5. Bottiger M and Heller L: Experiences from vaccination and revaccination of teenage girls with three different rubella vaccines. J Biol Stand 4:107-114, 1976. 6. Freis PC, Sussman EK and Shearin R: Sero-immunity screening of adolescent girls in a military population to determine susceptibility to the rubella virus. Milit. Med 141 (10):684-5, 1976. 7. Hendershot GE: Pregnant Workers in the United States. Advance data (Vital & Health Statistics of NCHS, DHEW, USPHS, HRA) 11:1-4, 1977.
ACKNOWLEDGMENTS Special thanks to the Memorial-Sloan Kettering Cancer Center's Employee Health Service staff and D. Robinson. Parts of this study were funded by Merck, Sharp & Dohme. The original version of this paper was presented at the Annual Meeting of the Society for Epidemiologic Research, June 1978, Iowa City, IA.
A Rubella Screening and Immunization Program In an Adolescent Clinic CATHEY E. FALVO, MD, MPH, KAREN E. WEISS, RN, MS, and SHARI M. Liss The present United States practice concerning rubella vaccine emphasizes immunization of preschool children. This approach appears to have prevented epidemic spread of rubella but has not adequately protected susceptible* women of childbearing age who are at risk of having babies with congenital rubella (CR). The rubella outbreak in Casper, Wyoming2 among junior and senior high school children, after a campaign to vaccinate the preschool and elementary school children in that city, indicated a potential problem in control of rubella. The recent outbreak in Hawaii3 among From the Virus Research Laboratory, Department of Pediatrics, The Roosevelt Hospital, New York City. Address reprint requests to Dr. Cathey E. Falvo, Virus Research Laboratory, Department of Pediatrics, The Roosevelt Hospital, 428 West 59 Street, New York, NY 10019. Ms. Weiss has recently completed the American Nurses' Association's certification program in Community Health Nursing Practice. This paper, submitted to the Journal April 17, 1978, was revised and accepted for publication October 6, 1978. *The term "susceptible(s)" will be used to indicate a person(s) with a rubella Hemagglutination Inhibition Antibody (HAI) titer of less than 1:8 as tested by the CDC method.'
AJPH March, 1979, Vol. 69, No. 3
young adults, despite a 95 per cent vaccination rate among school children, emphasizes the continuing risk of rubella among susceptible adults, especially the pregnant woman. Adolescent girls represent one potential high-risk group for contracting rubella during pregnancy. A rubella screening and vaccination program was developed for this group during 1974 at the Roosevelt Hospital in New York City. The purpose of the program was: a) to screen all women (10 to 21 years of age) attending the pediatric outpatient department (OPD) for rubella susceptibility*; b) to vaccinate all those found to be susceptible and who were not likely to become pregnant in the next three months. This paper outlines the results of this program.
Methods The adolescent outpatient program is part of the comprehensive care program within the pediatric OPD. Most of the patients are Hispanic and come from low income families. They are usually seen by the same primary care team 283
PUBLIC HEALTH BRIEFS
TABLE I-Adolescent Women Receiving Rubella Screening and Vaccination by Year Screened
Susceptible (%)
Year
1975 1976 1977 1978*
TOTAL:
284 411 699 374 1768
50 94 123 88 355
(17.6) (22.8) (17.5)
(23.5) (20.1)
Vaccinated (%) 19 41 17 31 134
(35.0) (43.6) (13.8) (41.9) (37.7)
*January 1, 1975-July 1, 1978
and are encouraged to make appointments in advance so that their medical record will be available. All adolescents are expected to receive a complete health history, physical assessment, and screening laboratory examination once a year. Starting in October 1974, a rubella HAI titer has been included in the laboratory screening tests on all adolescent women whether or not they had a history of rubella disease or vaccination. All those found to be susceptible to rubella are mailed a letter in English and Spanish explaining the risks of rubella in pregnancy and encouraging them to return for vaccination. An informed consent form is included for parental signature. Those patients vaccinated are given an appointment in two to three months to confirm seroconversion. Counseling about rubella is carried out by a team member. All laboratory slips of adolescents screened for rubella between January 1975 and July 1978 were reviewed and an updated list of susceptibles was compiled. The medical records of all the susceptibles were reviewed to corroborate vaccination and follow-up status with that reported by the teams to the Virus Research Laboratory. Finally, charts of all adolescent women visiting the clinic during April 1977 were reviewed to determine the extent of staff compliance with the policy of obtaining the rubella HAI titer.
Results Sera from 1,768 adolescent women were tested for rubella HAI titer (Table 1). Overall, 20.1 per cent (355) of the patients screened were susceptible. The follow-up vaccination rate was 37.7 per cent over the three-year period with yearly variations ranging from 13.8 to 43.6 per cent. Among the 134 vaccinees, 91 had been reported to the Virus Research Laboratory and 43 (32 per cent of the vaccinees) were identified through the chart review. As of December 31, 1977, 84 per cent of the vaccinees had returned to confirm seroconversion. The seroconversion rate for the group tested was 95 per cent. During the month of April 1977, 147 adolescent women visited the clinic. Review of 145 charts (two could not be located) revealed that 61 had serum for rubella HAI titer drawn during the April visit and 47 had had the serum drawn within the preceding 12 months. Thus, 74 per cent (108 of the 284
145) of adolescent women seen had had appropriate rubella serologic screening (Table 2).
Discussion Although the screening and especially the vaccination of adolescent women in our clinic is less than complete, we believe this project should continue. The reasons for our failure to screen and vaccinate more of our adolescents are multiple. From the less than full compliance in drawing blood for rubella serology and the incomplete reporting to the Virus Research Laboratory, it is clear that more education of clinic personnel is needed. Although bilingual letters were mailed to the susceptible women, many of our patients claim they did not receive mail from us. Our population is known to change addresses frequently and to use several surnames. Also difficult to assess is how many of our patients can read either English or Spanish well enough to understand the contents of the letter. By requiring the adolescent (and her parents if possible) to sign an informed consent, we place a further burden on the administration of the program. Some of our patients are unwilling to sign any document, others forget to get parental permission or their parents refuse to sign.
Concllusion Rubella screening and vaccination should continue for high-risk groups of women. Our experiences show that we are reducing the susceptible pool of women in the childbearing years by 30 percent. There are four times a young woman may be screened for rubella susceptibility; as part of an adolescent health evaluation, as a requirement of employment or entrance to college or vocational school, as part of the premarital examination, or during the antepartum examination. The Advisory Committee on Immunization Practices of the United States Public Health Service in its most recent recommendations on the use of rubella vaccine,4 does em-
TABLE 2-Evaluation of Compliance of Rubella Screening for Adolescent Women by Provider Team April 1977 Adolescent Women N Screened
Compliance Team
A B C D
TOTAL
N Seen
Before April
April
%
30 52 40 23
10 11 23
73.3 67.3 92.5
3
12 24 14 11
145
47
61
84.4
60.8
AJPH March, 1979, Vol. 69, No. 3
PUBLIC HEALTH BRIEFS
phasize prenatal screening for rubella with vaccination of susceptibles at the time of delivery. In view of the problems illustrated by our program, we feel strongly that rubella should be attacked on a broad base. One plan might encompass the following steps: 1) continue the current practice of vaccinating all preschool children starting at 15 months of age; 2) develop an appropriate surveillance of nine- or 10-year-olds to monitor continuing efficacy of the vaccine; and 3) develop programs to screen women of childbearing age for rubella susceptibility. Congenital rubella should become a disease of the past.
REFERENCES 1. Center for Disease Control. A Procedural Guide to the Performance of the Standardized Rubella Hemagglutinin-Inhibition Test. U.S. Department of Health, Education, and Welfare, Mental Services and Mental Health Administration. Center for Disease Control, Atlanta, GA, October 1970. 2. Klock LE and Rachelefsky GS: Failure of rubella herd immunity during an epidemic. N Engl J Med 288:69-72, 1973. 3. Rubella-Hawaii, MMWR 26:244-247, July 29, 1977. 4. Rubella Vaccine-Recommendation of the U.S. Public Health Service Advisory Committee on Immunization Practices. MMWR 26:385-391, November 25, 1977.
Rubella Screening and Follow-up Immunization in Vermont GAIL J. POVAR, MD, MPH, MARY MALONEY, MD, WILLIAM N. WATSON, MD, A. MARSHALL MCBEAN, MD, MSC, AND GREGORY GIGUERE, MS
Introduction In 1976, Schoenbaum estimated that without immunization the cost of the congenital rubella syndrome (CRS) to the public was $35/female, while the cost of immunization was $3/female. (This latter figure included the cost of side effects of the immunization.) These calculations suggest that the immunization of females of childbearing age against rubella is a cost effective measure in the prevention of CRS.' In 1969, the first rubella vaccines were licensed in the United States. Since then, both the American Academy of Pediatrics and the U.S. Public Health Service have recommended immunization of all children between the ages of one year and puberty.2 Despite the existence of rubella vaccine, the percentage of postpubertal women with no rubella antibody has not changed: 10 to 20 per cent are still susceptible to infection.3-5 A significant population is therefore still at risk of producing children with CRS. For four years, the Vermont State Health Department has provided free serologic testing for rubella. Results of the tests are sent to the patient's physician. Records maintained at the Health Department identify the population at risk, and the records show that 13 per cent of women tested-the national average-are seronegative for rubella. To date, we are aware of only one published study, in Colorado, which has Address reprint requests to Dr. Gail J. Povar, 1934 Columbia Pike, Apartment 9, Arlington, VA 22204. At the time of the study, Drs. Povar and Maloney were students at the University of Vermont College of Medicine; they are currently residents in medicine at George Washington University Medical Center and Hartford Hospital (CT) respectively. Dr. Watson was on field assignment from CDC, Bureau of Epidemiology to the Vermont State Department of Health at the time of the study; he is currently resident in child psychiatry, University of Pittsburgh. At the time of the study, Dr. McBean and Mr. Giguere were with the Vermont Department of Health. This paper, submitted to the Journal May 18, 1978, was revised and accepted for publication August 9, 1978.
AJPH March, 1979, Vol. 69, No. 3
attempted to evaluate the rate of follow-up immunization. That survey, conducted by questionnaires mailed to a sample of women who had been screened, found a follow-up immunization rate of 50 per cent. Unfortunately, the Colorado data were based on only a 30 per cent return rate of questionnaires.3 The goal of our study was to estimate the rate of follow-up immunization of seronegative women against rubella in the state of Vermont.
Methods The study was based on a probability sample of all women found to be seronegative (rubella hemaglutination inhibition antibody titre I < 8) in the months January 1976 through June 1976, as listed in the records of the Public Health Laboratory. These 579 women represented approximately 13 per cent of the 4,452 serologies. The time period chosen allowed a full eight-month interval for all study cases, thereby permitting inclusion of susceptible pregnant women who had to deliver before being immunized. Health Department records are classed as "prenatal" or "routine" according to the labeling done by the physician at the time of drawing the sample. Routine tests predominate. The total sample size of 330 was stratified to include all prenatal patients (142) and every third routine patient (188). We stratified the data for prenatal/routine patients because we felt the delay imposed by pregnancy might result in decreased follow-up in that group. On the other hand, presence in a hospital at the time of delivery might enhance the pregnant woman's chance for follow-up; the routine patient could be lost after the titer was drawn. Data were analyzed separately for Chittenden County and the rest of Vermont. Of the 330 samples, 115 came from physicians' offices in Chittenden County, while 215 came from offices in all other counties of the state. Chittenden County, the most populous in the state, includes Burlington, Vermont's largest city and its commercial center, the Uni285
confirms the observations of many others.5 6 Second, an active EHS was a suitable location for establishing a rubella screening and immunization program. The screening was easily incorporated into the routine pre-employment health examination. Most importantly, we have been reasonably successful in vaccinating the susceptible women in our program. In post-pubescent rubella vaccine campaigns, both pregnancy and vaccine reactions are of concern. Pregnancy was infrequent in our study population. Overall, in the United States, pregnant workers comprise 8.8 per cent of the ".ever-married women" of reproductive age currently employed.7 Thus a program which is based in the work force could provide an acceptable area for rubella screening and vaccination programs. Side reactions were not a problem in our study population. Those individuals with complaints serious enough to report to EHS for medical attention had conditions unrelated to rubella immunization. A study to follow both an immunized and a control group for concurrent symptoms would be a useful contribution. Our experience demonstrates that a rubella screening and immunization program for women employees, which includes an informed consent and discussion period, successfully captures an "at-risk" population and provides continuing health education.
REFERENCES 1. Judson FN, Shaw BS and Vernon TM: Mandatory premarital rubella serologic testing in Colorado: A preliminary report. JAMA 729:1200-1202, 1974. 2. Fox JP, Rainey HS, Hall CE, et al: Rubella vaccine in postpubertal women: Experience in western Washington state. JAMA 236:837-843, 1976. 3. New York State Public Health Law 2803; Section 720.6. 4. Center for Disease Control. A Procedural Guide to the Performance of the Standardized Rubella Hemagglutination-Inhibition Test. U.S. Department of Health, Education, and Welfare, Mental Services and Mental Health Administration. Center for Disease Control, Atlanta, GA, October 1970. 5. Bottiger M and Heller L: Experiences from vaccination and revaccination of teenage girls with three different rubella vaccines. J Biol Stand 4:107-114, 1976. 6. Freis PC, Sussman EK and Shearin R: Sero-immunity screening of adolescent girls in a military population to determine susceptibility to the rubella virus. Milit. Med 141 (10):684-5, 1976. 7. Hendershot GE: Pregnant Workers in the United States. Advance data (Vital & Health Statistics of NCHS, DHEW, USPHS, HRA) 11:1-4, 1977.
ACKNOWLEDGMENTS Special thanks to the Memorial-Sloan Kettering Cancer Center's Employee Health Service staff and D. Robinson. Parts of this study were funded by Merck, Sharp & Dohme. The original version of this paper was presented at the Annual Meeting of the Society for Epidemiologic Research, June 1978, Iowa City, IA.
A Rubella Screening and Immunization Program In an Adolescent Clinic CATHEY E. FALVO, MD, MPH, KAREN E. WEISS, RN, MS, and SHARI M. Liss The present United States practice concerning rubella vaccine emphasizes immunization of preschool children. This approach appears to have prevented epidemic spread of rubella but has not adequately protected susceptible* women of childbearing age who are at risk of having babies with congenital rubella (CR). The rubella outbreak in Casper, Wyoming2 among junior and senior high school children, after a campaign to vaccinate the preschool and elementary school children in that city, indicated a potential problem in control of rubella. The recent outbreak in Hawaii3 among From the Virus Research Laboratory, Department of Pediatrics, The Roosevelt Hospital, New York City. Address reprint requests to Dr. Cathey E. Falvo, Virus Research Laboratory, Department of Pediatrics, The Roosevelt Hospital, 428 West 59 Street, New York, NY 10019. Ms. Weiss has recently completed the American Nurses' Association's certification program in Community Health Nursing Practice. This paper, submitted to the Journal April 17, 1978, was revised and accepted for publication October 6, 1978. *The term "susceptible(s)" will be used to indicate a person(s) with a rubella Hemagglutination Inhibition Antibody (HAI) titer of less than 1:8 as tested by the CDC method.'
AJPH March, 1979, Vol. 69, No. 3
young adults, despite a 95 per cent vaccination rate among school children, emphasizes the continuing risk of rubella among susceptible adults, especially the pregnant woman. Adolescent girls represent one potential high-risk group for contracting rubella during pregnancy. A rubella screening and vaccination program was developed for this group during 1974 at the Roosevelt Hospital in New York City. The purpose of the program was: a) to screen all women (10 to 21 years of age) attending the pediatric outpatient department (OPD) for rubella susceptibility*; b) to vaccinate all those found to be susceptible and who were not likely to become pregnant in the next three months. This paper outlines the results of this program.
Methods The adolescent outpatient program is part of the comprehensive care program within the pediatric OPD. Most of the patients are Hispanic and come from low income families. They are usually seen by the same primary care team 283
PUBLIC HEALTH BRIEFS
TABLE I-Adolescent Women Receiving Rubella Screening and Vaccination by Year Screened
Susceptible (%)
Year
1975 1976 1977 1978*
TOTAL:
284 411 699 374 1768
50 94 123 88 355
(17.6) (22.8) (17.5)
(23.5) (20.1)
Vaccinated (%) 19 41 17 31 134
(35.0) (43.6) (13.8) (41.9) (37.7)
*January 1, 1975-July 1, 1978
and are encouraged to make appointments in advance so that their medical record will be available. All adolescents are expected to receive a complete health history, physical assessment, and screening laboratory examination once a year. Starting in October 1974, a rubella HAI titer has been included in the laboratory screening tests on all adolescent women whether or not they had a history of rubella disease or vaccination. All those found to be susceptible to rubella are mailed a letter in English and Spanish explaining the risks of rubella in pregnancy and encouraging them to return for vaccination. An informed consent form is included for parental signature. Those patients vaccinated are given an appointment in two to three months to confirm seroconversion. Counseling about rubella is carried out by a team member. All laboratory slips of adolescents screened for rubella between January 1975 and July 1978 were reviewed and an updated list of susceptibles was compiled. The medical records of all the susceptibles were reviewed to corroborate vaccination and follow-up status with that reported by the teams to the Virus Research Laboratory. Finally, charts of all adolescent women visiting the clinic during April 1977 were reviewed to determine the extent of staff compliance with the policy of obtaining the rubella HAI titer.
Results Sera from 1,768 adolescent women were tested for rubella HAI titer (Table 1). Overall, 20.1 per cent (355) of the patients screened were susceptible. The follow-up vaccination rate was 37.7 per cent over the three-year period with yearly variations ranging from 13.8 to 43.6 per cent. Among the 134 vaccinees, 91 had been reported to the Virus Research Laboratory and 43 (32 per cent of the vaccinees) were identified through the chart review. As of December 31, 1977, 84 per cent of the vaccinees had returned to confirm seroconversion. The seroconversion rate for the group tested was 95 per cent. During the month of April 1977, 147 adolescent women visited the clinic. Review of 145 charts (two could not be located) revealed that 61 had serum for rubella HAI titer drawn during the April visit and 47 had had the serum drawn within the preceding 12 months. Thus, 74 per cent (108 of the 284
145) of adolescent women seen had had appropriate rubella serologic screening (Table 2).
Discussion Although the screening and especially the vaccination of adolescent women in our clinic is less than complete, we believe this project should continue. The reasons for our failure to screen and vaccinate more of our adolescents are multiple. From the less than full compliance in drawing blood for rubella serology and the incomplete reporting to the Virus Research Laboratory, it is clear that more education of clinic personnel is needed. Although bilingual letters were mailed to the susceptible women, many of our patients claim they did not receive mail from us. Our population is known to change addresses frequently and to use several surnames. Also difficult to assess is how many of our patients can read either English or Spanish well enough to understand the contents of the letter. By requiring the adolescent (and her parents if possible) to sign an informed consent, we place a further burden on the administration of the program. Some of our patients are unwilling to sign any document, others forget to get parental permission or their parents refuse to sign.
Concllusion Rubella screening and vaccination should continue for high-risk groups of women. Our experiences show that we are reducing the susceptible pool of women in the childbearing years by 30 percent. There are four times a young woman may be screened for rubella susceptibility; as part of an adolescent health evaluation, as a requirement of employment or entrance to college or vocational school, as part of the premarital examination, or during the antepartum examination. The Advisory Committee on Immunization Practices of the United States Public Health Service in its most recent recommendations on the use of rubella vaccine,4 does em-
TABLE 2-Evaluation of Compliance of Rubella Screening for Adolescent Women by Provider Team April 1977 Adolescent Women N Screened
Compliance Team
A B C D
TOTAL
N Seen
Before April
April
%
30 52 40 23
10 11 23
73.3 67.3 92.5
3
12 24 14 11
145
47
61
84.4
60.8
AJPH March, 1979, Vol. 69, No. 3
PUBLIC HEALTH BRIEFS
phasize prenatal screening for rubella with vaccination of susceptibles at the time of delivery. In view of the problems illustrated by our program, we feel strongly that rubella should be attacked on a broad base. One plan might encompass the following steps: 1) continue the current practice of vaccinating all preschool children starting at 15 months of age; 2) develop an appropriate surveillance of nine- or 10-year-olds to monitor continuing efficacy of the vaccine; and 3) develop programs to screen women of childbearing age for rubella susceptibility. Congenital rubella should become a disease of the past.
REFERENCES 1. Center for Disease Control. A Procedural Guide to the Performance of the Standardized Rubella Hemagglutinin-Inhibition Test. U.S. Department of Health, Education, and Welfare, Mental Services and Mental Health Administration. Center for Disease Control, Atlanta, GA, October 1970. 2. Klock LE and Rachelefsky GS: Failure of rubella herd immunity during an epidemic. N Engl J Med 288:69-72, 1973. 3. Rubella-Hawaii, MMWR 26:244-247, July 29, 1977. 4. Rubella Vaccine-Recommendation of the U.S. Public Health Service Advisory Committee on Immunization Practices. MMWR 26:385-391, November 25, 1977.
Rubella Screening and Follow-up Immunization in Vermont GAIL J. POVAR, MD, MPH, MARY MALONEY, MD, WILLIAM N. WATSON, MD, A. MARSHALL MCBEAN, MD, MSC, AND GREGORY GIGUERE, MS
Introduction In 1976, Schoenbaum estimated that without immunization the cost of the congenital rubella syndrome (CRS) to the public was $35/female, while the cost of immunization was $3/female. (This latter figure included the cost of side effects of the immunization.) These calculations suggest that the immunization of females of childbearing age against rubella is a cost effective measure in the prevention of CRS.' In 1969, the first rubella vaccines were licensed in the United States. Since then, both the American Academy of Pediatrics and the U.S. Public Health Service have recommended immunization of all children between the ages of one year and puberty.2 Despite the existence of rubella vaccine, the percentage of postpubertal women with no rubella antibody has not changed: 10 to 20 per cent are still susceptible to infection.3-5 A significant population is therefore still at risk of producing children with CRS. For four years, the Vermont State Health Department has provided free serologic testing for rubella. Results of the tests are sent to the patient's physician. Records maintained at the Health Department identify the population at risk, and the records show that 13 per cent of women tested-the national average-are seronegative for rubella. To date, we are aware of only one published study, in Colorado, which has Address reprint requests to Dr. Gail J. Povar, 1934 Columbia Pike, Apartment 9, Arlington, VA 22204. At the time of the study, Drs. Povar and Maloney were students at the University of Vermont College of Medicine; they are currently residents in medicine at George Washington University Medical Center and Hartford Hospital (CT) respectively. Dr. Watson was on field assignment from CDC, Bureau of Epidemiology to the Vermont State Department of Health at the time of the study; he is currently resident in child psychiatry, University of Pittsburgh. At the time of the study, Dr. McBean and Mr. Giguere were with the Vermont Department of Health. This paper, submitted to the Journal May 18, 1978, was revised and accepted for publication August 9, 1978.
AJPH March, 1979, Vol. 69, No. 3
attempted to evaluate the rate of follow-up immunization. That survey, conducted by questionnaires mailed to a sample of women who had been screened, found a follow-up immunization rate of 50 per cent. Unfortunately, the Colorado data were based on only a 30 per cent return rate of questionnaires.3 The goal of our study was to estimate the rate of follow-up immunization of seronegative women against rubella in the state of Vermont.
Methods The study was based on a probability sample of all women found to be seronegative (rubella hemaglutination inhibition antibody titre I < 8) in the months January 1976 through June 1976, as listed in the records of the Public Health Laboratory. These 579 women represented approximately 13 per cent of the 4,452 serologies. The time period chosen allowed a full eight-month interval for all study cases, thereby permitting inclusion of susceptible pregnant women who had to deliver before being immunized. Health Department records are classed as "prenatal" or "routine" according to the labeling done by the physician at the time of drawing the sample. Routine tests predominate. The total sample size of 330 was stratified to include all prenatal patients (142) and every third routine patient (188). We stratified the data for prenatal/routine patients because we felt the delay imposed by pregnancy might result in decreased follow-up in that group. On the other hand, presence in a hospital at the time of delivery might enhance the pregnant woman's chance for follow-up; the routine patient could be lost after the titer was drawn. Data were analyzed separately for Chittenden County and the rest of Vermont. Of the 330 samples, 115 came from physicians' offices in Chittenden County, while 215 came from offices in all other counties of the state. Chittenden County, the most populous in the state, includes Burlington, Vermont's largest city and its commercial center, the Uni285
