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In the absence of natural boosting

In the absence of natural boosting....

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10828509&dopt=Abstract

 
Vet Parasitol 2000 Jun 10;90(1-2):25-35 Related Articles, Books, LinkOut
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Determination of duration of immunity of calves vaccinated with the Theileria annulata schizont cell culture vaccine.

Beniwal RK, Sharma RD, Nichani AK.

Department of Veterinary Medicine, CCS Haryana Agricultural University, Haryana, India.

Bovine tropical theileriosis caused by Theileria annulata is a serious haemoprotozoan disease of cattle affecting exotic cattle, their crossbreeds and young indigenous calves. Cell culture vaccines have been developed and used effectively in various countries for the control of this disease. However, the duration of immunity provided by these vaccines is poorly understood. The present experiments were planned to study the duration of immunity in animals after vaccination with the T. annulata (Hisar) schizont cell culture vaccine. Two groups of calves were vaccinated and challenged after a period of 3 and 6 months, respectively. There was no fever in any of the vaccinated calves after challenge. However, the vaccinated animals exhibited mild to moderate enlargement of lymph nodes and parasitological reactions. The parasitological reactions were very mild in calves challenged after 3 months and moderate in calves challenged after 6 months. There was a mild but significant decrease in the haematological values of calves after challenge. A significant rise in the anti-theilerial antibody titres was observed in all calves after vaccination, which increased further, by many folds after challenge. On the other hand, all the challenge control calves showed symptoms of acute theileriosis and died. The observations suggested that the T. annulata (Hisar) schizont cell culture vaccine provided immunity in vaccinated animals for at least 6 months in the absence of field tick challenge. However, there was some decline in immunity after 6 months, if the animals are not exposed to ticks during this period.

PMID: 10828509 [PubMed - indexed for MEDLINE]

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10813152&dopt=Abstract

 
Epidemiol Infect 2000 Apr;124(2):263-71 Related Articles, Books, LinkOut

Secondary measles vaccine failures identified by measurement of IgG avidity: high occurrence among teenagers vaccinated at a young age.

Paunio M, Hedman K, Davidkin I, Valle M, Heinonen OP, Leinikki P, Salmi A, Peltola H.

Department of Public Health, University of Helsinki, Finland.

Failure to seroconvert (primary vaccine failure) is believed to be the principal reason (approx. > 95%) why some vaccinees remain susceptible to measles and is often attributed to the persistence of maternal antibodies in children vaccinated at a young age. Avidity testing is able to separate primary from secondary vaccine failures (waning and/or incomplete immunity), but has not been utilized in measles epidemiology. Low-avidity (LA) and high-avidity (HA) virus-specific IgG antibodies indicate primary and secondary failure, respectively. Measles vaccine failures (n = 142; mean age 10.1 years, range 2-22 years) from an outbreak in 1988-9 in Finland were tested for measles-virus IgG avidity using a protein denaturating EIA. Severity of measles was recorded in 89 failures and 169 non-vaccinees (mean age 16.2 years, range 2-22 years). The patients with HA antibodies (n = 28) tended to have clinically mild measles and rapid IgG response. Among failures vaccinated at < 12, 12-15 and > 15 months of age with single doses of Schwarz-strain vaccine in the 1970s, 50 (95% CI 1-99), 36 (CI 16-56) and 25% (CI 8-42) had HA antibodies, respectively. When a single measles, mumps and rubella (MMR) vaccine had been given after 1982 at 15 months of age, only 7% (CI 0-14) showed HA antibodies. Omitting re-vaccinees and those vaccinated at < 15 months, Schwarz-strain recipients had 3.6 (CI 1.1-11.5) higher occurrence of HA responses compared to MMR recipients. Apart from one municipality, where even re-vaccinees had high risk of primary infection, 89% (CI 69 to approximately 100) of the infected re-vaccinees had an HA response. Secondary measles-vaccine failures are more common than was more previously thought, particularly among individuals vaccinated in early life, long ago, and among re-vaccinees. Waning immunity even among individuals vaccinated after 15 months of age, without the boosting effect of natural infections should be considered a relevant possibility in future planning of vaccination against measles.

PMID: 10813152 [PubMed - indexed for MEDLINE]

AN: 20271260


http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10023894&dopt=Abstract

 
Lancet 1999 Jan 9;353(9147):98-102 Related Articles, Books, LinkOut
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Effect of subclinical infection on maintaining immunity against measles in vaccinated children in West Africa.

Whittle HC, Aaby P, Samb B, Jensen H, Bennett J, Simondon F.

MRC Laboratories, Fajara, Banjul, The Gambia. whittle@commit.gm

BACKGROUND: Despite a high coverage with measles vaccines in parts of west Africa, epidemics of measles occur with reduced severity in an increasing proportion of older children who have been vaccinated. We examined the effect of exposure to natural measles on immunity in vaccinated children. METHODS: Our study was carried out in 1992 during an epidemic of measles in Niakhar, a rural area of Senegal with about 27,000 inhabitants who mostly live in compounds that include several households; within each household people live in different huts. Vaccine coverage in Niakhar was 81% at the time of our study. We measured haemagglutinin-inhibiting antibody at exposure and twice thereafter (after 4-5 weeks and at 6 months) in 36 vaccinated and 87 unvaccinated children. The frequency of measles and subclinical measles--defined as a four-fold or greater rise in antibody titre without clinical signs or symptoms--was related to intensity of exposure according to whether the index case was in the same hut, household, or compound. FINDINGS: Clinical measles occurred in 20 (56%) of 36 unvaccinated children and in one (1%) of 87 vaccinated children. Subclinical measles occurred in 39 (45%) of 86 vaccinated children who were exposed to measles and in four (25%) of 16 unvaccinated children. The frequency was inversely related to pre-exposure antibody concentration (p<0.001 for trend) and directly related to intensity of exposure (p=0.002 for trend). Antibody concentrations in subclinical cases increased on average by 45-fold and remained raised for at least 6 months. INTERPRETATION: Increased antibody titre after subclinical measles may be common in vaccinated children in West Africa where the intensity of exposure is high. As measles vaccination coverage increases, the circulation of wild measles will decrease, and vaccine-induced antibody is less likely to be boosted. Thus, new epidemics, albeit milder in form, may occur in vaccinated areas which should be recognised in campaigns to eradicate measles.

PMID: 10023894 [PubMed - indexed for MEDLINE]

AN: 99146499


http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10588085&dopt=Abstract

 
Am J Epidemiol 1999 Dec 1;150(11):1238-49 Related Articles, Books, LinkOut

Modeling the impact of subclinical measles transmission in vaccinated populations with waning immunity.

Mossong J, Nokes DJ, Edmunds WJ, Cox MJ, Ratnam S, Muller CP.

Department of Biological Sciences, University of Warwick, Conventry, England.

An increasing body of evidence suggests that a substantial proportion of individuals who respond to measles vaccine display an antibody boost accompanied by mild or no symptoms on exposure to wild virus. It is unknown whether this emerging class of individuals can support transmission. The epidemiologic consequences of vaccinated individuals able to transmit virus are investigated using a mathematical model. Parameters for this model are estimated using regression analysis on a Canadian serologic data set. The authors confirm that neutralizing antibodies are decaying significantly in absence of circulating virus. Based on a protective threshold plaque reduction neutralization (PRN) titer of 120, the authors estimate the mean duration of vaccine-induced protection in absence of reexposure to be 25 years (95% confidence interval (CI) 18, 48). After long-term absence of circulating virus, the mathematical model predicts that 80% (95% CI 65, 91) of all seroconverted vaccinees have titers below the protective threshold. In this case, elimination of measles virus cannot be achieved by a single-dose routine vaccination strategy if the basic reproduction number in vaccinated individuals exceeds 1.24 (95% CI 1.10, 1.53). For this reason, there is a need to establish the intensity and duration of infectiousness in vaccinated individuals.

PMID: 10588085 [PubMed - indexed for MEDLINE]

AN: 20053306


A report of diphtheria surveillance from a rural medical college hospital.
Ray,-S-K; Das-Gupta,-S; Saha,-I
J-Indian-Med-Assoc. 1998 Aug; 96(8): 236-8.
Journal-of-the-Indian-Medical-Association;
0019-5847
English
A 5-year sentinel surveillance of diphtheria from 1989 to 1993 was undertaken at a rural medical college hospital. No significant change in the number of diphtheria cases was observed in spite of sustained high level of diphtheria, pertussis, tetanus vaccine-3 doses (DPT3) coverage. Most of the diphtheria cases occurred during July to November. Age distribution of diphtheria cases showed that more than 75% occurred above 2 years age (except in 1989) and around 65% cases above 3 years age. The age shift in diphtheria signified success of primary diphtheria immunisation, as well as indicated the lack of coverage with booster doses at appropriate ages. Because of high coverage with primary diphtheria immunisation there was decrease in circulating toxigenic C diphtheriae resulting in less natural boosting of antibody titre. Thus, in absence of booster immunisation, the older children and adults were more vulnerable to diphtheria. The findings of the study justified the need of emphasising importance of booster diphtheria immunisation at appropriate ages for effective control of diphtheria.
National-Library-of-Medicine
AN: 99047981


http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8972678&dopt=Abstract

 
Epidemiol Infect 1996 Dec;117(3):519-24 Related Articles, Books, LinkOut

A study of maternally derived measles antibody in infants born to naturally infected and vaccinated women.

Brugha R, Ramsay M, Forsey T, Brown D.

Immunisation Division, Public Health Laboratory Service (PHLS) Communicable Disease Surveillance Centre, London.

Maternal, cord and infant measles antibody levels were measured and compared in a group of 411 vaccinated mothers and 240 unvaccinated mothers, and their babies, between 1983 and 1991. Maternal and cord sera were tested by haemagglutination inhibition and/or enzyme-linked immunosorbent assay, and plaque reduction neutralization tests were also used to test infant sera. Geometric mean titres were significantly higher in the unvaccinated than in the vaccinated mothers (P < 0.001). Infants born to mothers with a history of measles had higher antibody levels at birth than infants of vaccinated mothers and, although the difference narrowed over time, continued to have higher levels up to 30 weeks of age. Between 5 and 7 months of age significantly more of the children of vaccinated mothers had plaque reduction neutralization antibody levels below that which would interfere with vaccination. As the boosting effect of circulating natural measles disappears, earlier measles vaccination may need to be considered, perhaps as part of a two-dose policy.

PMID: 8972678 [PubMed - indexed for MEDLINE]

AN: 97128008


http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8970216&dopt=Abstract

 
Pediatr Infect Dis J 1996 Dec;15(12):1082-6 Related Articles, Books, LinkOut
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Measles vaccine effectiveness and duration of vaccine-induced immunity in the absence of boosting from exposure to measles virus.

Guris D, McCready J, Watson JC, Atkinson WL, Heath JL, Bellini WJ, Polloi A.

Center for Disease Control and Prevention, Atlanta, GA, USA.

BACKGROUND: It is unknown whether vaccine-induced immunity is lifelong in the absence of periodic exposure to measles virus. After 27 years of no known exposure to measles, an outbreak in Palau in 1993 offered the opportunity to study this issue and the measles vaccine effectiveness. METHODS: Household contacts of a sample of confirmed cases were interviewed for exposure, symptoms and vaccination status verified by records. Serum from symptomatic contacts was tested for measles antibodies. RESULTS: Among 78 contacts 4 of 5 (80%) unvaccinated, 4 of 35 (11%) 1-dose vaccine recipients and none of 38 (0%) > 1-dose recipients developed measles. Effectiveness of 1-dose vaccine was 86% (95% confidence interval, 60 to 95%). An additional dose significantly reduced the risk of measles (P = 0.048). Time since vaccination was not a significant risk factor for developing measles (relative risk, 1.6; 95% confidence interval, 0.3 to 9.4; persons vaccinated > 15 years ago vs. < 5 years ago). CONCLUSIONS: Similar to the estimates previously obtained in the area, measles vaccine effectiveness in Palau was lower than the estimates obtained in the US. A second dose of vaccine further reduced the risk for developing measles. We found no evidence that waning immunity was an important problem in this limited population with no known previous exposure to measles virus. The small number of vaccinated contacts precludes a definitive assessment.

PMID: 8970216 [PubMed - indexed for MEDLINE]

AN: 97125112

A contrary view. - SM


http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7489768&dopt=Abstract

 
Eur J Epidemiol 1995 Feb;11(1):107-17 Related Articles, Books, LinkOut

Diphtheria: changing patterns in the developing world and the industrialized world.

Galazka AM, Robertson SE.

Global Programme for Vaccines and Immunization, World Health Organization, Geneva, Switzerland.

In the past, diphtheria was considered one of the most serious childhood diseases because it took a heavy toll in health and life among preschool-aged children. Prior to the widespread availability of diphtheria toxoid, nearly 70% of cases were in children younger than 15 years of age. In the industrialized countries, immunization against diphtheria became widespread in the 1940s and 1950s. This led to a marked decrease in the incidence of diphtheria. There was also a decrease in circulating toxigenic Corynebacterium diphtheriae organisms, resulting in less natural boosting of antibody levels. This had led to gaps in the immunity of the adult population. Since 1990, diphtheria has made a spectacular comeback in several European countries, with a high proportion of cases in adults. In developing countries, immunization of infants with diphtheria toxoid was introduced with the Expanded Programme on Immunization in the late 1970s. Coverage rose slowly to 46% in 1985 and 79% in 1992. Because the pool of immunized persons is not yet large, the process of maintaining immunity still operates through natural mechanisms, including frequent skin infections caused by C. diphtheriae. But recently, several developing countries where coverage has been high for 5-10 years have reported diphtheria outbreaks. These outbreaks have been characterized by high case fatality rates, a large proportion of patients with complications, and their occurrence in both young and older age groups. In all countries, priority should be given to efforts to reach at least 90% coverage with three doses of diphtheria toxoid in children below one year of age. In countries where diphtheria has been successfully controlled, immunity levels should be maintained by booster doses.

Publication Types:
  • Review
  • Review, Tutorial


PMID: 7489768 [PubMed - indexed for MEDLINE]

AN: 96104944


http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7687111&dopt=Abstract

 
: Ann Trop Paediatr 1993;13(2):153-8 Related Articles, Books, LinkOut

Persistence of antibody at 18 months following vaccination of young Gambian infants with PRP-OMPC Haemophilus influenzae type b conjugate vaccine.

Mulholland EK, Todd J, Rowe M, Campbell H, Byass P, Vella PP, Ahonkhai VI, Greenwood BM.

Medical Research Council Laboratories, The Gambia, West Africa.

The rate of decline in anti-PRP antibody levels was measured in two groups of Gambian children who had been given PRP-OMPC at 1 and 3 months or 2 and 4 months of age. In the younger group (n = 70), the geometric mean titre fell from 1.32 micrograms/ml at 4 months to 0.44 micrograms/ml at 18 months. In the older group (n = 54), the geometric mean titre fell from 1.18 micrograms/ml at 5 months to 0.46 micrograms/ml at 18 months. The proportion of vaccinated children with antibody levels over 1.0 microgram/ml fell from 54% 1 month after the second dose of vaccine to 27% at the age of 18 months, while the proportion with levels over 0.15 micrograms/ml fell from 82% to 60%, with no significant differences observed between the vaccination groups. For those children who did not show evidence of environmental boosting, the half-life of anti-PRP antibody was about 100 days. This did not differ between the groups. These findings suggest that to provide lasting immunity PRP-OMPC should be given with a late booster dose at 12-15 months, as is the current practice in the USA. The need for a late booster dose may limit the value of this vaccine in developing countries where vaccination of children is difficult after the 1st year of life.

Publication Types:
  • Clinical Trial
  • Randomized Controlled Trial


PMID: 7687111 [PubMed - indexed for MEDLINE]

AN: 93319237


http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7227654&dopt=Abstract

 
Dev Biol Stand 1981;47:257-9 Related Articles, Books, LinkOut

Experience of vaccination with inactivated poliomyelitis vaccines in Iceland.

Gudnadottir M.

Iceland, as a few other European countries, has used inactivated vaccine against poliomyelitis from the beginning in 1956. No cases of paralytic polio occurred since 1960. For 17 years neither isolations of poliovirus nor suspected cases of the clinical disease have been recorded. Studies on neutralizing antibodies in sera of vaccinees were not too encouraging after 4 injections. A 5th vaccination of IPV was therefore given to those children who lacked antibodies to any type of poliovirus. One month after the 5th injection 70% had antibodies against all 3 types of poliovirus and only 2% lacked antibodies against both types 1 and 3. In countries where no virus to boost immunity exists any longer during the life of an individual it may be necessary to secure booster effects at regular intervals after primary vaccination and later in life. This will be included in the vaccination schedule against polio in Iceland.

PMID: 7227654 [PubMed - indexed for MEDLINE]

AN: 81189486


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