Accuracy of the National Polio Surveillance Project data in
Rajasthan.
Paul Y.
S.P. Medical College, Bikaner, Rajasthan, India. devisharan_@yahoo.com
According to the National Polio Surveillance Project (NPSP) there were 15
polio cases in Rajasthan during 2000. Close scrutiny of the Line List of AFP
cases shows that there were at least 58 polio cases, many cases had been
wrongly classified. Cases of vaccine
associated paralytic poliomyelitis (VAPP)
and vaccine failure had been missed.
Observational methods in epidemiologic assessment of
vaccine effectiveness.
Torvaldsen S, McIntyre PB.
National Centre for Immunisation Research and Surveillance of Vaccine
Preventable Diseases, The Children's Hospital at Westmead, NSW. SirandaT@chw.edu.au
Observational methods are important in the measurement of vaccine
effectiveness (VE) as experimental designs cannot be used for measurement of
vaccines already on the vaccination schedule. Furthermore, efficacy measured
in clinical trials under ideal conditions may differ to effectiveness in the
field under non-ideal conditions and in different populations. In addition to
post-licensure surveillance, observational VE studies are particularly
important when disease incidence does not predictably decrease with increased
vaccine coverage, when high
proportions of vaccine failure among reported cases suggest a problem with the
vaccine or when issues arise that were not predicted in pre-licensure
evaluations. Commonly used study types for evaluating VE include cohort
studies, household contact studies, case-control studies, the screening method
and case-cohort studies. There are many potential biases in all observational
VE studies which should be considered in the study design and analysis stage.
Of the five observational study types reviewed, cohort studies undertaken
during an outbreak investigation offer the simplest means of VE estimation and
is the preferred study design where the situation permits. Where this is not
possible the screening method is the most economical and rapid method. It is
essential that the effectiveness of all vaccination programs be evaluated. As
new vaccines are introduced to the schedule, booster doses are added and the
timing of doses changed, the role of observational methods in the evaluation
of VE will become even more important. To date, few observational VE studies
have been undertaken in Australia, suggesting the under-utilisation of these
methods.
Impact of meningococcal C conjugate vaccine in the UK.
Balmer P, Borrow R, Miller E.
Meningococcal Reference Unit, Manchester PHL, Withington Hospital.
This review details the impact of the introduction of meningococcal serogroup
C conjugate (MCC) vaccines in the UK. An overall reduction of 86.7% in the
incidence of serogroup C infection in the targeted age groups has been
observed from 1999 to 2001, with a concomitant decrease in deaths, from 67 in
1999 to 5 in 2001. The enhanced surveillance programme initiated to complement
the introduction of MCC vaccines has been essential in generating data
relating to vaccine coverage, vaccine failures and efficacy estimates.
Vaccine coverage has exceeded 80% in
all age groups targeted and up to the end of 2001, 25 confirmed and 1 probable
vaccine failure have been observed in England and Wales. Efficacy
estimates for England up to September 2001 were 91.5% in infants receiving
three doses of MCC vaccine and 89.3% in toddlers receiving one dose of MCC
vaccine (England). There is some evidence of herd immunity in unvaccinated
cohorts of the target age groups, ranging from a reduction in disease
incidence of 34% in 9-14 year olds to 61% in 15-17 year olds. Surveillance of
the genotypic and phenotypic characteristics of invasive and carriage isolates
has shown no evidence to date of capsular switching from serogroup C to
serogroup B.
Twin studies of immunogenicity--determining the genetic
contribution to vaccine failure.
Tan PL, Jacobson RM, Poland GA, Jacobsen SJ, Pankratz VS.
Department of Paediatrics, National University Hospital, Singapore.
CONTEXT: Estimating the magnitude of
the genetic contribution to the overall variation of antibody levels among
individuals should help clarify the role of genetic association in the
biological mechanism of vaccine response and failure. This, in turn, should
help guide the design of improved vaccines with enhanced efficacy.
OBJECTIVE: To explore the magnitude of genetic influence on antibody levels
following measles, mumps and rubella vaccines. DESIGN: Cross-sectional survey
study. SETTING: Olmsted County, Minnesota. PARTICIPANTS: Healthy twin-pairs.
Of the 100 twin-pairs enrolled, 45 were monozygotic. INTERVENTIONS:
Determinations of zygosity, vaccine status, and quantitative IgG to measles,
mumps, and rubella. Main outcome measure: Heritability (ratio of genetic
variance to total variance). RESULTS: The number of vaccine-doses, the age at
initial immunization, and the time between immunization and sampling did not
differ between monozygotic and dizygotic twin pairs. The genetic variance -
the variance in antibody levels presumably due to genetic effects - was 0.49
for measles, 0.54 for mumps, and 0.13 for rubella. Heritability, the ratio of
genetic variance to total variance, was 88.5% for measles, with the lower
bound of a one-sided 95% confidence interval equal to 52.4%. The heritability
was, for mumps, 38.8% with a lower bound of 1.60%. The heritability for
rubella was 45.7% with a lower bound of 4.94%. CONCLUSION:
Our data support the concept that
genetic influences play a substantial role in the variation of antibody levels
following immunization against measles and, to a lesser extent, mumps and
rubella.
Oxford Vaccine Group, John Radcliffe Hospital, Oxford, United Kingdom. pheath@sghms.ac.uk
Haemophilus influenzae type b (Hib) conjugate vaccines have proved extremely
efficacious in healthy children. True Hib vaccine failures are rare. Hib
conjugate vaccines were introduced for routine immunization in the United
Kingdom and the Republic of Ireland in 1992.
Coincident with this, active
prospective and national surveillance via pediatricians, microbiologists, and
public health physicians was commenced to assess the clinical and
immunological factors associated with vaccine failure. During the 6 years of
the study, 115 children with true vaccine failure were reported. Of the
children who were vaccinated before 12 months of age, a clinical risk factor
was detected in 20%, an immunological deficiency was detected in 30%, and one
or both were detected in 44%. Children who were vaccinated after 12 months of
age were more likely to have one or both factors (67%). Thirty percent (33 of
105) of children with true vaccine failure had a low Hib antibody response
(concentration, <1.0 microg/mL) after disease, but the majority then responded
to a further dose of Hib vaccine. Children who develop Hib disease despite
vaccination deserve further clinical and immunological evaluation.
Use of a microquantity enzyme immunoassay in a large-scale
study of measles, mumps and rubella immunity in Italy.
Condorelli F, Stivala A, Gallo R, Marino A, Battaglini CM, Messina A, Russo
G, Castro A, Scalia G.
Institute of Microbiology, University of Catania, Italy.
The seroprevalence of antibodies to measles, mumps, and rubella viruses (MMR)
was determined in 1498 subjects in Catania, Italy, ranging in age from 1 month
to 25 years. The study population was divided into seven age groups and
screened by enzyme immunoassay using microquantities (10 microl) of whole
blood collected by fingerprick on filter paper discs. The results showed that
seroconversion for measles (87.6%) and mumps (73.2%) occurred between 6 and 10
years of age. The seroprevalence of antibodies to rubella virus increased
slowly through the age groups, reaching the highest rate (93.3%) between 16
and 20 years of age. Passively transmitted maternal antibodies to mumps and
rubella were absent in babies between 5 and 8 months of age, and a few cases
positive for measles antibodies were found among babies 6 and 7 months of age.
The enzyme immunoassay was demonstrated to be suitable for low-cost
large-scale screening for MMR immunity.
The rate of vaccine failure was also
evaluated and found to be 9.5% for the measles virus, 12.9% for the mumps
virus and 0.0% for the rubella virus.
[Vaccination against Haemophilus influenzae type b in the
Valencia Community: efficacy and failure of vaccinations]
[Article in Spanish]
Morant Gimeno A, Diez Domingo J, Rosales Marza A, Moreno Munoz R, Lopez
Garcia P, Herrero Galiana A, Gimeno Cardona C, Brimes Solanes J.
Instituto de Salud Carlos III, Unitat d'Investigacio Trinitat, Valencia.
OBJECTIVE: To study Haemophilus influenzae type b (Hib) conjugate vaccine
effectivity and vaccine failures in the Valencian Community of Spain where
vaccine can be obtained, but is not scheduled as a routine immunization.
PATIENTS AND METHODS: A prospective surveillance system where pediatricians
and microbiologists of all public hospitals of the Valencian Community
reported cases of invasive Hib disease in children (under 15 years of age).
Vaccination status (number of doses, dates and type of vaccine) in each case
was obtained. RESULTS: Of 23 cases reported from December 1, 1995 to November
30, 1996, two had received at least one dose of Hib vaccine. One was a true
vaccine failure and the other an apparent vaccine failure. Estimating a
vaccine coverage of 32.5% of the children less than 5 years old, the direct
vaccine effectivity was 90.6% (IC 95%: 27.9-98.8%). CONCLUSIONS: Hib conjugate
vaccine is effective in the Valencian Community, however,
there is still invasive disease due to
the low vaccine coverage and some vaccine failures.
DISCLAIMER: All
information, data, and material contained, presented, or provided here is for
general information purposes only and is not to be construed as reflecting the
knowledge or opinions of the publisher, and is not to be construed or intended
as providing medical or legal advice. The decision whether or not to vaccinate
is an important and complex issue and should be made by you, and you alone, in
consultation with your health care provider.
