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Outbreaks in highly vaccinated populations

Outbreaks in highly vaccinated populations

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Vaccine 2002 Jan 15;20(7-8):1134-40 Related Articles, Books, LinkOut
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Immunogenicity of second dose measles-mumps-rubella (MMR) vaccine and implications for serosurveillance.

Pebody RG, Gay NJ, Hesketh LM, Vyse A, Morgan-Capner P, Brown DW, Litton P, Miller E.

Sero-Epidemiology Unit, Immunisation Division, PHLS Communicable Disease Surveillance Centre, 61 Colindale Avenue, London, UK. rpebody@phls.org.uk

Measles and mumps, but not rubella, outbreaks have been reported amongst populations highly vaccinated with a single dose of measles-mumps-rubella (MMR) vaccine. Repeated experience has shown that a two-dose regime of measles vaccine is required to eliminate measles. This paper reports the effect of the first and second MMR doses on specific antibody levels in a variety of populations.2-4 years after receiving a first dose of MMR vaccine at age 12-18 months, it was found that a large proportion of pre-school children had measles (19.5%) and mumps (23.4%) IgG antibody below the putative level of protection. Only a small proportion (4.6%) had rubella antibody below the putative protective level. A total of 41% had negative or equivocal levels to one or more antigens. The proportion measles antibody negative (but not rubella or mumps) was significantly higher in children vaccinated at 12 months of age than at 13-17 months. There was no evidence for correlation of seropositivity to each antigen, other than that produced by a small excess of children (1%) negative to all three antigens. After a second dose of MMR, the proportion negative to one or more antigens dropped to <4%. Examination of national serosurveillance data, found that following an MR vaccine campaign in cohorts that previously received MMR, both measles and rubella antibody levels were initially boosted but declined to pre-vaccination levels within 3 years.Our study supports the policy of administering a second dose of MMR vaccine to all children. However, continued monitoring of long-term population protection will be required and this study suggests that in highly vaccinated populations, total measles (and rubella) IgG antibody levels may not be an accurate reflection of protection. Further studies including qualitative measures, such as avidity, in different populations are merited and may contribute to the understanding of MMR population protection.

PMID: 11803074 [PubMed - indexed for MEDLINE]

AN: 21662161


http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11384530&dopt=Abstract

 
: Emerg Infect Dis 2001 May-Jun;7(3):463-5 Related Articles, Books, LinkOut

Outbreak of influenza in highly vaccinated crew of U.S. Navy ship.

Earhart KC, Beadle C, Miller LK, Pruss MW, Gray GC, Ledbetter EK, Wallace MR.

Naval Medical Center San Diego, San Diego, California 92134, USA. kcearhart@nmcsd.med.navy.mil

An outbreak of influenza A (H3N2) occurred aboard a U.S. Navy ship in February 1996, despite 95% of the crew's having been appropriately vaccinated. Virus isolated from ill crew members was antigenically distinct from the vaccination strain. With an attack rate of 42%, this outbreak demonstrates the potential for rapid spread of influenza in a confined population and the impact subsequent illness may have upon the workplace.

PMID: 11384530 [PubMed - indexed for MEDLINE]

AN: 21278470


http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11030058&dopt=Abstract

Bull Soc Pathol Exot 2000 Jul;93(3):202-5 Related Articles, Books, LinkOut

[Genetic evolution under vaccine pressure: the Bordetella pertussis model]

[Article in French]

Simondon F, Guiso N.

Unite de recherche sur les maladies infectieuses et parasitaires, IRD (ex-ORSTOM), Montpellier, France.

A possible genetic selective pressure related to the long-term use of vaccines has been the object of recent theoretical thought and publications. For more than thirty years, an effective vaccine has been in use against whooping cough on a wide scale basis in several countries. Thus, the Bordetella pertussis model may contribute to the analysis of an evolutionary risk linked to the vaccine. To maintain and improve the control of whooping cough, better vaccination coverage must be achieved in countries where prevalence is low. In countries where high vaccination coverage has been achieved over a long period, a trend toward the resurgence of the disease has been observed. Efforts are therefore now being directed toward primary vaccination and boosters. These two targets require new vaccines with fewer side effects. Outbreaks in highly vaccinated populations have been reported, raising the issues of vaccine efficacy, of the long-term effect of vaccines on the transmission of the disease, and of genetic selective pressure. Time trend modifications of circulating strains related to vaccination practices and vaccine types have been observed and are compatible with a selective pressure of the vaccine on related pathogens. However, evidence for a causal relation is lacking. In order to monitor and understand the various effects the vaccine may be having on the effectiveness of immunisation against whooping cough, further surveillance is needed, integrating a standardised characterisation of circulating strains and vaccines by way of a space-time sampling model.

Publication Types:
  • Review
  • Review, Tutorial


PMID: 11030058 [PubMed - indexed for MEDLINE]

AN:  20484564


http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10469786&dopt=Abstract

 
Pediatrics 1999 Sep;104(3 Pt 1):561-3 Related Articles, Books, LinkOut
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Varicella outbreaks after vaccine licensure: should they make you chicken?

Buchholz U, Moolenaar R, Peterson C, Mascola L.

Epidemic Intelligence Service, Epidemiology Program Office, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA. ubuchholz@dhs.co.la.ca.us

In 1998, 3 years after vaccine licensure, child care centers (CCC) in Los Angeles County continued to report varicella outbreaks. We investigated outbreaks at 2 CCCs to determine the cause for them, such as low vaccination coverage levels or unexpected low vaccine effectiveness. We collected information on past history of varicella, illness during the outbreak, and prior varicella vaccination among CCC attendees. We found that CCC "H" had a vaccination coverage of 87% (34/39) compared with 30% (6/20) in CCC "L." The overall attack rate was lower in CCC "H" (31%) than in "L" (61%; P value =.03). Vaccine effectiveness for any varicella was 71% in "H" and 100% in "L." Vaccinated children with varicella had milder disease than unvaccinated. In conclusion, we found varicella outbreaks in CCCs with both high and low vaccination coverage. Vaccine effectiveness was within the range predicted by the literature. Vaccination led to a lower attack rate in the highly vaccinated CCC and appeared to protect from severe disease.

PMID: 10469786 [PubMed - indexed for MEDLINE]

AN:  99400883

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MMWR Morb Mortal Wkly Rep 1999 Jan 8;47(51-52):1109-11 Related Articles, Books, LinkOut

Transmission of measles among a highly vaccinated school population--Anchorage, Alaska, 1998.

During August 10-November 23, 1998, 33 confirmed measles cases were reported to the Anchorage Department of Health and Human Services and the Alaska Department of Health and Social Services (ADHSS). Of these, 26 cases were confirmed by positive rubeola IgM antibody test, and seven met the clinical case definition. This was the largest outbreak of measles in the United States since 1996. This report summarizes results of the epidemiologic investigation conducted by ADHSS and underscores the importance of second-dose requirements for measles vaccine.

PMID: 9921727 [PubMed - indexed for MEDLINE]

AN:  99118700


http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10559534&dopt=Abstract

 
Vaccine 1999 Oct 29;17 Suppl 3:S47-52 Related Articles, Books, LinkOut
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Measles elimination: progress and challenges.

Cutts FT, Henao-Restrepo A, Olive JM.

Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London, UK. f.cutts@lshtm.ac.uk

The accelerating progress in reducing measles incidence and mortality in many parts of the world has led to calls for its global eradication during the next 10-15 years. Three regions have established goals of elimination of indigenous transmission of measles. The strategy used in the Americas of a mass 'catchup' campaign of children 9 months to 15 years of age, high coverage through routine vaccination of infants, intensive surveillance and follow-up campaigns to prevent excessive build-up of susceptibles has had great success in reducing measles transmission close to zero. However, while these developments are impressive, much remains to be done to reduce measles-associated mortality in western and central Africa, where less than half of children are currently receiving measles vaccine and half a million children die from measles each year.The obstacles to global measles eradication are perceived to be predominantly political and financial. There are also technical questions, however. These include the refinement of measles elimination strategies in the light of recent outbreaks in the Americas; the implications of the HIV epidemic for measles elimination, issues around injection safety, and concerns about the possibility that secondary vaccine failures will contribute in sustaining transmission in highly vaccinated populations. The global priorities are to improve measles control in low income countries, increase awareness among industrialized countries of the importance of measles, and conduct studies to answer the technical questions about measles elimination strategies.

Publication Types:
  • Review
  • Review, Tutorial


PMID: 10559534 [PubMed - indexed for MEDLINE]

AN:  20027647


http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9764341&dopt=Abstract

 
Trans R Soc Trop Med Hyg 1998 Mar-Apr;92(2):227-30 Related Articles, Books, LinkOut

Measles antibody levels in a vaccinated population in Brazil.

Cox MJ, Azevedo RS, Massad E, Fooks AR, Nokes DJ.

Department of Biological Sciences, University of Warwick, Coventry, UK.

An epidemiological study of measles-specific immunoglobulin G antibody levels was conducted using a representative sample of a vaccinated suburban population in Sao Paulo State, Brazil. The study aimed to determine immunity status in relation to age and infection or vaccination experience. 549 age-structured samples of sera, collected in 1990, were screened and calibrated to the international reference serum, using measles nucleoprotein in an enzyme immunoassay. In the age group with direct experience of vaccination (9 months to 15 years), whether routine or campaign, over 90% had detectable antibody > or = 50 miu/mL. However, 14% of these had antibody concentrations between 50 and 100 miu/mL and 30% between 50 and 255 miu/mL. In those over 15 years of age, 94% had antibody levels > 255 miu/mL, assumed to be the result of past infection. The study suggested that, within highly vaccinated populations, a proportion of individuals had measles antibody levels which may be insufficient to protect against reinfection or clinical disease. The implications of these results, and similar findings elsewhere, in relation to the persistence of measles requires investigation; this has particular relevance in Sao Paulo following the recent measles outbreak.

PMID: 9764341 [PubMed - indexed for MEDLINE]

AN:  98436832


http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9310216&dopt=Abstract

 
MMWR Morb Mortal Wkly Rep 1997 Sep 5;46(35):822-6 Related Articles, Books, LinkOut

Pertussis outbreak -- Vermont, 1996.

Pertussis is increasingly recognized as a disease that affects older children and adults, including fully vaccinated persons. This report describes a statewide outbreak of pertussis in Vermont (1995 population: 584,771) in 1996 in a highly vaccinated population, affecting primarily school-aged children and adults, and underscores the need to include pertussis in the differential diagnosis of cough illness in persons of all ages.

PMID: 9310216 [PubMed - indexed for MEDLINE]

AN:  97454141


http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8943928&dopt=Abstract

 
CMAJ 1996 Nov 15;155(10):1407-13 Related Articles, Books, LinkOut

Comment in:
  • Can Med Assoc J. 1996 Nov 15;155(10):1423-6
  • Can Med Assoc J. 1997 Apr 1;156(7):979, 982


Outbreak of measles in a highly vaccinated secondary school population.

Sutcliffe PA, Rea E.

Community Medicine Residency Program, University of Toronto, Ont.

OBJECTIVE: To examine the factors associated with measles vaccine effectiveness and the effect of two doses of vaccine on measles susceptibility during an outbreak. DESIGN: Retrospective cohort study. SETTING: A secondary school in the City of Toronto. SUBJECTS: The entire school population (1135 students 14 to 21 years of age). MAIN OUTCOME MEASURES: Risk of measles during an outbreak associated with age at first measles vaccination, length of time since vaccination, vaccination before 1980 and whether date of vaccination was estimated; vaccine efficacy of one dose versus two doses. RESULTS: Eighty-seven laboratory-confirmed or clinically confirmed cases of measles were identified (for an attack rate of 7.7%). The measles vaccination rate was 94.2%, and 10% of the students had received two doses of measles vaccine before the outbreak. Among those who had received only one dose of vaccine, vaccination at less than 15 months of age was associated with vaccine failure (relative risk 3.62, 95% confidence interval 2.32 to 5.66). There was no increased risk of vaccine failure associated with length of time since vaccination once the relative risk was adjusted for age at vaccination in a stratified analysis. Vaccination before 1980 and an estimated date of vaccination were not associated with increased risk of vaccine failure. Administration of a second dose of vaccine during the outbreak was not protective. Two doses of vaccine given before the outbreak conferred significant protection, and the relative risk of failure after one dose versus two doses was 5.0 (95% confidence interval 1.25 to 20.15). Of the 87 cases, 76 (87%) could have been prevented had all the students received two doses of measles vaccine before the outbreak, with the first at 12 months of age or later. CONCLUSIONS: Delayed primary measles vaccination (at 15 months of age or later) significantly reduced measles risk at later ages. However, revising the timing of the current 12-month dose would leave children vulnerable during a period in which there is increased risk of complications. The findings support a population-based two-dose measles vaccination strategy for optimal measles control and eventual disease elimination.

PMID: 8943928 [PubMed - indexed for MEDLINE]

AN: 97099351

Note:  This presupposes that re-vaccination works not only in the short-term, but in the long-term.  Unfortunately, there is evidence that re-vaccination does not work in the long-term.  Even Dr. Samuel Katz, the inventor of the measles vaccine, has admitted as much.  (More links will be provided as time permits.) - SM


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CMAJ 1996 Nov 15;155(10):1423-6 Related Articles, Books, LinkOut

Comment on:
  • Can Med Assoc J. 1996 Nov 15;155(10):1407-13


Elimination of measles in the Americas.

Furesz J.

Of the 5551 confirmed measles cases reported in 1995 in the Americas, 2301 (41%) occurred in Canada. In this issue (see pages 1407 to 1413) Drs. Penny A. Sutcliffe and Elizabeth Rea describe a measles outbreak that occurred during that year in a highly vaccinated secondary school population in Toronto. Their findings support the use of a two-dose measles vaccination strategy. In this editorial the author explains how a two-dose strategy lowers the incidence of primary and secondary vaccine failures and thus reduces the number of susceptible people to below the outbreak threshold. Two-dose programs in Finland, Sweden and the United States have dramatically reduced the incidence rates of measles in those countries, and it is expected that the implementation of two-dose programs and "catch-up" campaigns in Canada and the remaining countries of the Americas will eliminate measles from the Western Hemisphere by the year 2000.

Publication Types:

  • Comment
  • Editorial


PMID: 8943930 [PubMed - indexed for MEDLINE]

AN: 97099353

Please see note above. - SM


http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7795768&dopt=Abstract

 
Arch Pediatr Adolesc Med 1995 Jul;149(7):774-8 Related Articles, Books, LinkOut

Mumps outbreak in a highly vaccinated school population. Evidence for large-scale vaccination failure.

Cheek JE, Baron R, Atlas H, Wilson DL, Crider RD Jr.

Division of Field Epidemiology, Centers for Disease Control and Prevention, Atlanta, GA, USA.

OBJECTIVES: To describe an outbreak and to identify risk factors for mumps occurring in a highly vaccinated high school population. (Note: Highly vaccinated means a population in which more than 95% have been vaccinated.) DESIGN AND PARTICIPANTS: Survey and cohort study of 307 (97%) of 318 students. OUTCOME MEASURES: Mumps was defined as an illness with 2 or more days of parotid swelling. Serologic confirmation of infection was obtained in eight cases, seven of which were evaluated for presence of IgM antibody using immunofluorescent antibodies. Vaccination records were verified for 297 (97%) students. RESULTS: Between October 3 and November 23, 1990, clinical mumps developed in 54 students (attack rate, 18%), 53 of whom had been vaccinated. Most cases (40 [77%] of 52) occurred 12 to 20 days after a school-wide pep rally. Immunofluorescent antibody testing of all seven specimens demonstrated IgM antibody to mumps. Risk factors for clinical mumps identified in multivariate analyses included female gender (odds ratio, 3.0; 95% confidence interval, 1.6 to 5.7) and source of vaccination other than the local public health clinic (students vaccinated by private providers [odds ratio, 3.0; 95% confidence interval, 1.3 to 5.2] or in other districts [odds ratio, 2.4; 95% confidence interval, 1.1 to 5.3]). CONCLUSIONS: The overall attack rate is the highest reported to date (and to our knowledge) for a population demonstrating virtually complete mumps vaccine coverage. Even verified documentation of vaccination may not be an accurate indicator of an individual's protection against mumps. Vaccination failure may play an important role in contemporary mumps outbreaks. We found no evidence to indicate that waning immunity (secondary vaccine failure) contributed significantly to this outbreak. A second dose of mumps vaccine, as recommended using measles-mumps-rubella vaccine, could potentially prevent similar outbreaks in secondary school populations in the future.

PMID: 7795768 [PubMed - indexed for MEDLINE]

AN: 95316124

See note above. - SM


http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8296777&dopt=Abstract

 
Am J Epidemiol 1994 Jan 1;139(1):77-90 Related Articles, Books, LinkOut

Comment in:


Outbreaks in highly vaccinated populations: implications for studies of vaccine performance.

Fine PE, Zell ER.

Immunization Division, Centers for Disease Control and Prevention, Atlanta, GA 30333.

Most of the factors associated with the failure of a vaccination to provide protective immunity are not distributed uniformly or randomly within populations. This paper explores the extent to which a nonrandom distribution of vaccination failures and the selection of exceptional situations for investigation may influence estimates of vaccine performance. The authors show that outbreak investigations will tend to underestimate vaccination efficacy, and that the extent of underestimation will be related directly to the size of the epidemic triggering an investigation, the vaccination coverage in the community, and the extent of clustering of vaccination failures in the population; it will be related inversely to the size of and contact intensity within the investigated community. These potential sources of bias are not the only problems that arise in estimating vaccine efficacy, but they should be taken into consideration when analyzing and interpreting outbreak situations. The fact that outbreak investigations carried out within the United States during the past decade have provided estimates of measles vaccination efficacy on the order of 95% is consistent with a somewhat higher overall "true" efficacy of current vaccines and procedures in the total population. It is important to understand better the frequency, distribution, and risk factors for vaccination failures in populations.

PMID: 8296777 [PubMed - indexed for MEDLINE]


http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1861205&dopt=Abstract
 
J Pediatr 1991 Aug;119(2):187-93 Related Articles, Books, LinkOut

Mumps outbreak in a highly vaccinated population.

Hersh BS, Fine PE, Kent WK, Cochi SL, Kahn LH, Zell ER, Hays PL, Wood CL.

Division of Immunization, Centers for Disease Control, Atlanta, Georgia 30033.

From October 1988 to April 1989, a large mumps outbreak occurred in Douglas County, Kansas. Of the 269 cases, 208 (77.3%) occurred among primary and secondary school students, of whom 203 (97.6%) had documentation of mumps vaccination. Attack rates were highest for students attending junior high school (8.0%), followed by high school (2.0%) and elementary school (0.7%). A retrospective cohort study conducted at one junior high school with an attack rate of 12.9% did not find age at vaccination or type of vaccine received (single or combined antigen) to be risk factors for vaccine failure. Students vaccinated more than 4 years before the outbreak appeared to have a higher attack rate than those vaccinated more recently (relative risk (RR) = 4.3; 95% confidence interval (CI) = 0.6, 30.0); however, this association did not exist when risk was evaluated based on number of vaccine doses received. Students who had documentation of receiving only one dose of vaccine were at greater risk than those who had received two doses (RR = 5.2; 95% CI = 1.0, 206.2). Overall, vaccine effectiveness among Douglas County junior high school students was estimated to be 83% (95% CI = 57%, 94%). These data suggest that mumps vaccine failure and the failure to vaccinate have contributed to the relative resurgence of mumps observed in the United States since 1986. The recent change in immunization policy to recommend a two-dose schedule of measles-mumps-rubella vaccine should help reduce the occurrence of mumps outbreaks in highly vaccinated populations.

PMID: 1861205 [PubMed - indexed for MEDLINE]
 

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7621401&dopt=Abstract

 
Clin Microbiol Rev 1995 Apr;8(2):260-7 Related Articles, Books, LinkOut
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Measles control in the United States: problems of the past and challenges for the future.

Wood DL, Brunell PA.

Ahmanson Department of Pediatrics, Cedars-Sinai Medical Center, Los Angeles, California 90048, USA.

Elimination of indigenous measles from the United States has been a public priority since 1978. To assess the progress made toward this goal, we review the epidemiology of measles from 1963 to the present. From the 1970s through early into the recent measles epidemic, the majority of measles cases were in highly vaccinated, school-age children. This was due primarily to a 1 to 5% primary measles-mumps-rubella vaccine failure rate and nonrandom mixing patterns among school-age populations. To eliminate susceptible individuals in the school-age populations, a second dose of measles vaccine is now recommended between 5 and 6 years or 11 and 12 years by both the Advisory Committee on Immunization Practices and the American Academy of Pediatrics. Later in the epidemic, measles cases surged among unimmunized preschool children, especially among the poor in inner-city areas. Immunization rates have been documented to be low among preschool populations because of missed opportunities to administer vaccines at all health visits and barriers to access to immunizations. To raise immunization rates, the age for the first measles-mumps-rubella immunization was lowered to 12 to 15 months of age, federal immunization funding has increased, and new standards for immunization delivery have been developed and promulgated.

Publication Types:
  • Review
  • Review, Tutorial


PMID: 7621401 [PubMed - indexed for MEDLINE]

AN: 95346871


http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8277201&dopt=Abstract

 
: J Infect Dis 1994 Jan;169(1):77-82 Related Articles, Books, LinkOut

Sustained transmission of mumps in a highly vaccinated population: assessment of primary vaccine failure and waning vaccine-induced immunity.

Briss PA, Fehrs LJ, Parker RA, Wright PF, Sannella EC, Hutcheson RH, Schaffner W.

Division of Field Epidemiology, Centers for Disease Control and Prevention, Atlanta, Georgia.

From January to July 1991, an outbreak of mumps occurred in Maury County, Tennessee. At the primarily affected high school, where 98% of students and all but 1 student with mumps had been vaccinated before the outbreak, 68 mumps cases occurred among 1116 students (attack rate, 6.1%). Students vaccinated before 1988 (the first year mumps vaccination was required for school attendance in Tennessee) may have been at greater risk of mumps than those vaccinated later (65[6.1%] of 1001 vs. 2[2.2%] of 89; risk ratio, 2.9; 95% confidence interval, 0.7-11.6). Of 13 persons with confirmed mumps who underwent serologic testing, 3 lacked IgM antibody in well-timed acute- and convalescent-phase serum specimens. Vaccine failure accounted for a sustained mumps outbreak in a highly vaccinated population. Most mumps cases were attributable to primary vaccine failure. It is possible that waning vaccine-induced immunity also played a role.

PMID: 8277201 [PubMed - indexed for MEDLINE]

AN: 94103669


http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1994745&dopt=Abstract


 

 
Am J Public Health 1991 Mar;81(3):360-4 Related Articles, Books, LinkOut

A measles outbreak at a college with a prematriculation immunization requirement.

Hersh BS, Markowitz LE, Hoffman RE, Hoff DR, Doran MJ, Fleishman JC, Preblud SR, Orenstein WA.

Division of HIV/AIDS, Centers for Disease Control, Atlanta, GA 30333.

BACKGROUND. In early 1988 an outbreak of 84 measles cases occurred at a college in Colorado in which over 98 percent of students had documentation of adequate measles immunity (physician diagnosed measles, receipt of live measles vaccine on or after the first birthday, or serologic evidence of immunity) due to an immunization requirement in effect since 1986. METHODS. To examine potential risk factors for measles vaccine failure, we conducted a retrospective cohort study among students living in campus dormitories using student health service vaccination records. RESULTS. Overall, 70 (83 percent) cases had been vaccinated at greater than or equal to 12 months of age. Students living in campus dormitories were at increased risk for measles compared to students living off-campus (RR = 3.0, 95% CI = 2.0, 4.7). Students vaccinated at 12-14 months of age were at increased risk compared to those vaccinated at greater than or equal to 15 months (RR = 3.1, 95% CI = 1.7, 5.7). Time since vaccination was not a risk factor for vaccine failure. Measles vaccine effectiveness was calculated to be 94% (95% CI = 86, 98) for vaccination at greater than or equal to 15 months. CONCLUSIONS. As in secondary schools, measles outbreaks can occur among highly vaccinated college populations. Implementation of recent recommendations to require two doses of measles vaccine for college entrants should help reduce measles outbreaks in college populations.

PMID: 1994745 [PubMed - indexed for MEDLINE]

AN: 91135797

See note above. 


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: J Trop Pediatr 1991 Mar;37(2):71-6 Related Articles, Books, LinkOut

An outbreak of whooping cough in a highly vaccinated urban community.

Strebel P, Hussey G, Metcalf C, Smith D, Hanslo D, Simpson J.

Centre for Epidemiological Research, South African Medical Research Council, Tygerberg.

In 1950 a whole-cell pertussis vaccine was introduced in Cape Town and was followed by a marked decline in reported whooping cough mortality and morbidity. This resulted in reduced awareness of whooping cough as a clinical problem and, in recent years, no routine diagnostic tests for Bordetella pertussis have been performed. An outbreak of whooping cough occurred in Cape Town between 1 June 1988, and 31 May 1989, with 292 children admitted to hospital for whooping cough during this period (hospital admission rate in children under 5 years of age = 187 per 100,000). In an investigation of 239 children attending four pre-primary schools in the city, the whooping cough attack rate was 33 per cent, while pertussis vaccine coverage was 95 per cent. In the latter part of the outbreak nasopharyngeal swabs and serology were performed in patients presenting to a children's hospital with suspected whooping cough. Bordetella pertussis was isolated from 3 out of 34 (9 per cent) children tested and the first isolate was serotyped as type 1,2,4. Available clinical and laboratory evidence indicated that the organism responsible for the outbreak was Bordetella pertussis. Coverage studies for pertussis vaccine in Cape Town indicated that between 81 and 93 per cent of children were fully immunized by 13 months of age. These findings suggest that, since its introduction, the whole-cell pertussis vaccine produced in South Africa has been highly effective in controlling whooping cough. However, it was not able to prevent a moderate scale outbreak, even in the presence of high vaccination levels.

PMID: 2027168 [PubMed - indexed for MEDLINE]

AN: 91226008


http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2278542&dopt=Abstract

 
JAMA 1990 May 9;263(18):2467-71 Related Articles, Books, LinkOut

Comment in:


Mild measles and secondary vaccine failure during a sustained outbreak in a highly vaccinated population.

Edmonson MB, Addiss DG, McPherson JT, Berg JL, Circo SR, Davis JP.

Department of Pediatrics, University of Wisconsin, Madison 53792.

A prolonged school-based outbreak of measles provided an opportunity to study "vaccine-modified" mild measles and secondary vaccine failure. Thirty-six (97%) of 37 unvaccinated patients had rash illnesses that met the Centers for Disease Control clinical case definition of measles, but 29 (15%) of 198 vaccinated patients did not, primarily because of low-grade or absent fever. Of 122 patients with seroconfirmed measles, 10 patients (all previously vaccinated) had no detectable measles-specific IgM and significantly milder illness than either vaccinated or unvaccinated patients with IgM-positive serum. Of 108 vaccinated patients with seroconfirmed measles, 17 patients (16%) had IgM-negative serology or rash illnesses that failed to meet the clinical case definition; their mean age (13 years), age at the time of vaccination, and time since vaccination did not differ from those of other vaccinated patients. The occurrence of secondary vaccine failure and vaccine-modified measles does not appear to be a major impediment to measles control in the United States but may lead to underreporting of measles cases and result in overestimation of vaccine efficacy in highly vaccinated populations.

PMID: 2278542 [PubMed - indexed for MEDLINE]

AN: 90230400


http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2910058&dopt=Abstract


 

 
Am J Epidemiol 1989 Jan;129(1):173-82 Related Articles, Books, LinkOut

An explosive point-source measles outbreak in a highly vaccinated population. Modes of transmission and risk factors for disease.

Chen RT, Goldbaum GM, Wassilak SG, Markowitz LE, Orenstein WA.

Division of Immunization, Centers for Disease Control, Atlanta, GA.

In 1985, 69 secondary cases, all in one generation, occurred in an Illinois high school after exposure to a vigorously coughing index case. The school's 1,873 students had a pre-outbreak vaccination level of 99.7% by school records. The authors studied the mode of transmission and the risk factors for disease in this unusual outbreak. There were no school assemblies and little or no air recirculation during the schooldays that exposure occurred. Contact interviews were completed with 58 secondary cases (84%); only 11 secondary cases (19%) of these may have had exposure to the index case in the classrooms, buses, or out of school. With the use of the Reed-Frost epidemic model, only 22-65% of the secondary cases were likely to have had at least one person-to-person contact with the index case during class exchanges, suggesting that this mode of transmission alone could not explain this outbreak. A comparison of the first 45 cases and 90 matched controls suggested that cases were less likely than controls to have provider-verifiable school vaccination records (odds ratio (OR) = 8.1) and more likely to have been vaccinated at less than age 12 months (OR = 8.6) or at age 12-14 months (OR = 7.0). Despite high vaccination levels, explosive measles outbreaks may occur in secondary schools due to 1) airborne measles transmission, 2) high contact rates, 3) inaccurate school vaccination records, or 4) inadequate immunity from vaccinations at younger ages.

PMID: 2910058 [PubMed - indexed for MEDLINE]

AN: 89086385


http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2911293&dopt=Abstract


 

 
N Engl J Med 1989 Jan 12;320(2):75-81 Related Articles, Books, LinkOut

Patterns of transmission in measles outbreaks in the United States, 1985-1986.

Markowitz LE, Preblud SR, Orenstein WA, Rovira EZ, Adams NC, Hawkins CE, Hinman AR.

Division of Immunization, Centers for Disease Control, Atlanta, GA 30333.

Since the licensing of measles vaccine in 1963, the incidence of reported measles in the United States has declined to less than 2 percent of previous levels. To characterize the current epidemiology of measles in the United States, we analyzed measles outbreaks that occurred during 1985 and 1986. There were 152 outbreaks (defined as five or more cases related epidemiologically), which accounted for 88 percent of the cases reported during those two years. There were two major types of outbreaks: those in which most of the cases occurred among preschool-age children (those under 5 years of age) (26 percent) and those in which most of the cases occurred among school-age persons (those 5 to 19 years of age) (67 percent). The outbreaks among preschool-age children ranged in size from 5 to 945 cases (median, 13); a median of only 14 percent of the cases occurred in vaccinated persons, and a median of 45 percent of the cases were classified as preventable according to the current strategy. Outbreaks among school-age persons ranged in size from 5 to 363 cases (median, 25); a median of 60 percent of the cases occurred in vaccinated persons, and a median of only 27 percent of the cases were preventable. The outbreaks among preschool-age children indicate deficiencies in the implementation of the national measles-elimination strategy. However, the extent of measles transmission among highly vaccinated school-age populations suggests that additional strategies, such as selective or mass revaccination, may be necessary to prevent such outbreaks.

PMID: 2911293 [PubMed - indexed for MEDLINE]

AN: 89097101


http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=3826461&dopt=Abstract

 
Am J Public Health 1987 Apr;77(4):434-8 Related Articles, Books, LinkOut

Measles outbreak in a vaccinated school population: epidemiology, chains of transmission and the role of vaccine failures.

Nkowane BM, Bart SW, Orenstein WA, Baltier M.

An outbreak of measles occurred in a high school with a documented vaccination level of 98 per cent. Nineteen (70 per cent) of the cases were students who had histories of measles vaccination at 12 months of age or older and are therefore considered vaccine failures. Persons who were unimmunized or immunized at less than 12 months of age had substantially higher attack rates compared to those immunized on or after 12 months of age. Vaccine failures among apparently adequately vaccinated individuals were sources of infection for at least 48 per cent of the cases in the outbreak. There was no evidence to suggest that waning immunity was a contributing factor among the vaccine failures. Close contact with cases of measles in the high school, source or provider of vaccine, sharing common activities or classes with cases, and verification of the vaccination history were not significant risk factors in the outbreak. The outbreak subsided spontaneously after four generations of illness in the school and demonstrates that when measles is introduced in a highly vaccinated population, vaccine failures may play some role in transmission but that such transmission is not usually sustained.

PMID: 3826461 [PubMed - indexed for MEDLINE]

AN: 87154064


http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=65732&dopt=Abstract

 
N Engl J Med 1977 Mar 17;296(11):585-9 Related Articles, Books, LinkOut

Epidemic measles in a highly vaccinated population.

Shasby DM, Shope TC, Downs H, Herrmann KL, Polkowski J.

During November, 1975, to May, 1976, measles occurred at a rate of 20.3 cases per 1000 in a purported immunized population, of whom historical and serologic survey revealed that 9 per cent had no history of either measles illness or vaccination and 18 per cent did not have detectable measles antibody. Antibody was detectable in 92 per cent of those vaccinated at greater than or equal to 13 months, 80 per cent at 12 months and 67 per cent of those vaccinated when less than one year old (P less than 0.001), but no significant differences existed with increasing years since vaccination (P greater than 0.1). A second vaccination increased detectable antibody prevalence only in those originally vaccinated when less than nine months old (42 to 80 per cent, P less than 0.02). During a measles outbreak, more cases occurred in those receiving vaccine when less than 12 months old than in those vaccinated at greater than or equal to 12 months (37 per cent vs. 9 per cent, P less than 0.001). A second vaccination protected those originally vaccinated at less than 12 months (35 per cent ill without a second vaccination vs. 2 per cent with, P less than 0.001). Thus, a single measles vaccination of children less than 12 months old does not protect; a second vaccination will protect this group.

PMID: 65732 [PubMed - indexed for MEDLINE]

AN: 77123672


http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=6427582&dopt=Abstract

 
MMWR Morb Mortal Wkly Rep 1984 Jun 22;33(24):349-51 Related Articles, Books, LinkOut

Measles outbreak among vaccinated high school students--Illinois.

PMID: 6427582 [PubMed - indexed for MEDLINE]

From the article:

Editorial Note: This outbreak demonstrates that transmission of measles can occur within a school population with a documented immunization level of 100%. This level was validated during the outbreak investigation. Previous investigations of measles outbreaks among highly immunized populations have revealed risk factors such as improper storage or handling of vaccine, vaccine administered to children under 1 year of age, use of globulin with vaccine, and use of killed virus vaccine (1-5). However, these risk factors did not adequately explain the occurrence of this outbreak.

 

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