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.
Poor serologic responses five to seven years after
immunization with high and standard titer measles vaccines.
Whittle H, Aaby P, Samb B, Cisse B, Kanteh F, Soumare M, Jensen H, Bennett
J, Simondon F.
MRC Laboratories, Banjul, The Gambia. whittle@commit.gm
BACKGROUND: Few data exist on the persistence of measles antibodies after
vaccination of West African infants. Therefore we examined measles antibody
titers 5 to 7 years after children in rural Senegal had received high titer
Edmonston-Zagreb (EZ-HT), high titer Schwarz (SW-HT) or standard titer Schwarz
(SW-STD) measles vaccines in infancy. METHODS: Children had received either
high titer vaccines at 5 months of age or standard titer at 10 months of age.
Finger prick blood samples were tested for measles antibody 5 to 7 years later
by the hemagglutinin inhibition test. RESULTS: Persistence of antibody after
high titer vaccines was poor with the result that 39 and 50% of the EZ-HT and
the SW-HT groups had low titers of hemagglutinin inhibition measles antibodies
(< or =125 mIU/ml). Nineteen percent of the children in the SW-STD group had
low titers which is a lower prevalence than in the high titer groups [relative
risk (95% confidence intervals), 0.05 (0.28 to 0.88) vs. EZ-HT; relative risk,
0.38 (0.22 to 0.66) vs. SW-HT]. Geometric mean (95% confidence interval)
antibody titers in children with detectable values were 616 (435 to 871) in
the EZ-HT, 1106 (616 to 1866) in the SW-HT and 1271 (871 to 1741) mIU/ml in
the SW-STD groups, respectively. Multivariant regression analysis showed that
mean titers were 2.00 (1.03 to 3.89) times higher for children with low
prevaccination antibody titers (< or =125 mIU/ml) and 3.06 (1.90 to 4.94)
times higher if blood was collected in the rainy season. INTERPRETATION: Given
the rapid decline in antibody titers over a 5- to 6-year period in an area
where measles vaccine coverage was high, it seems likely that multiple dose
immunization schedules will be needed in the future to maintain protective
antibody concentrations (>125 mIU/ml) in West Africa.
The role of subclinical boosting by
exposure to natural measles and the possible role of malaria, which increases
immunoglobulin turnover, in influencing long term antibody persistence after
vaccination deserve further investigation.
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.
The Task Force for Child Survival and Development, The Carter Center, Atlanta,
GA 30307, USA.
BACKGROUND: Increases in measles
antibodies without rash-illnesses have been documented in previously
vaccinated children exposed to measles cases. The phenomenon has been
incompletely evaluated in young unvaccinated infants with immunity of maternal
origin. METHODS: Monthly cohorts of newborns were prospectively randomized to
vaccine and placebo control groups during a trial of high-titre vaccines in
Niakhar, Senegal. Measles antibodies were assayed in blood samples of enrolled
children collected at 5 months old, when controls received a placebo
injection, and at 10 months, when the placebo group was given measles vaccine.
Intensive prospective surveillance for measles was conducted throughout the
trial. RESULTS: One-fifth (n = 53) of the placebo controls seroconverted, with
known exposure to a measles case in only three of them. None of the
seroconverters developed a measles-like rash. Sixteen-fold or greater
increases in titres were noted in about one-quarter of them. Compared with
placebo controls who did not seroconvert, seroconverters were more likely to
have had exposure to a measles case and to travel, more likely to be boys than
girls, and had significantly lower baseline antibody titres. Measles was
endemic in the study area throughout the trial. Seroconversions did not
adversely effect subsequent nutritional indices or mortality. CONCLUSIONS:
Although laboratory errors and inadvertent injection of vaccine rather than
placebo may have played some role, they do not fully explain the above
observations, which are consistent with subclinical measles in the
seroconverters. The possible role of
subclinical measles in occult transmission, its potential effect on the type
and duration of subsequent immunity, and its impact on response to primary
vaccination need to be determined.
The effect of subclinical experimental Cowdria ruminantium
infection in ewes on the growth and milk consumption of pre-weaning lambs.
Martinez TA, Meltzer MI, Perry BD, Burridge MJ, Mahan SM.
Department of Pathobiology, College of Veterinary Medicine, University of
Florida, Gainesville 32611, USA. sumanmah@samara.co.zw
An alternative control option for heartwater (Cowdria ruminantium infection)
is the establishment and maintenance of endemic stability which would lessen
the existing dependence on acaricides.
In an endemically stable state, animals become infected by vaccination or
natural challenge at an early age, following which the immunity so created is
boosted by continuing tick challenge. In this study, growth rates,
health and hematological parameters were monitored at regular intervals for
lambs born to two matched groups of ewes until weaning at 4 mo of age. One
group of ewes was infected multiple times with Cowdria ruminantium; the other
group remained uninfected. The overall mean leucocyte count of lambs born to
infected ewes was significantly lower than that of lambs born to uninfected
ewes (P=0.04). However, there were few other significant differences in the
other hematological data between the two groups. The mean birth weight of
single lambs born to uninfected ewes (4.6 kg) was significantly higher than
the mean birth weight of single lambs born to infected ewes (4.4 kg) (P=0.02).
Trends in milk consumption and growth rates were similar for the two groups,
with few significant differences detected. Likewise, there were no significant
differences in the incidences of health problems or pre-weaning mortalities
between the two groups of lambs. The results of this study indicate that there
is no detectable effect on productivity of pre-weaning lambs when their dams
are carriers of C. ruminantium--a situation likely to occur in an endemically
stable state. Hence, maintenance of endemic stability would be a suitable
control option for heartwater.
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 seroconvertedvaccinees
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.
Vaccine-induced measles virus antibodies after two doses of
combined measles, mumps and rubella vaccine: a 12-year follow-up in two
cohorts.
Davidkin I, Valle M.
National Public Health Institute, Helsinki, Finland. Irja.Davidkin@ktl.fi
In Finland, a two-dose vaccination programme against measles, mumps and
rubella (MMR) was begun in 1982. The programme with high coverage (97-98%) has
eliminated these three diseases from Finland. The aim of the present study was
to follow up the kinetics of measles virus antibodies in MMR vaccinated
cohorts. We have followed the kinetics of measles virus antibody levels
induced by vaccination in the same individuals immunized with their first MMR
vaccine in 1982. After 12 years 80% of the original children remained
available for sampling. Antibodies to measles virus were measured by
haemagglutination inhibition (HI) and plaque reduction neutralization (NT)
techniques. The primary dose induced 99.4% seroconversion for measles with a
geometric mean HI antibody titre (GMT) of 1/269 (+/- 219), equivalent to 4304
mIU (milli-International Units) ml-1 in group A. The 12-year follow-up
specimens showed a measles seropositivity rate of 100% as assayed with the HI
and NT tests with a mean HI antibody titre of 1/39 (+/- 54), equivalent to 624
mIU ml-1. The vaccination-induced
measles virus antibodies decline in the absence of natural booster infections.
It is important to follow how long the protection achieved by the present
vaccine programme
will last after elimination of indigenous measles.
Increases in levels of antibody to hepatitis B surface
antigen in an immunized population.
Bulkow LR, Wainwright RB, McMahon BJ, Parkinson AJ.
Arctic Investigations Program, Centers for Disease Control and Prevention,
Anchorage, Alaska.
Hepatitis B vaccine is effective in preventing infection with hepatitis B
virus (HBV), but its duration of protection is unknown.
To examine the effect of exposure to
HBV on an immunized population, data were analyzed from a cohort of
Alaska Natives who were immunized and then followed up annually for 10 years.
A boost in antibody to hepatitis B
surface antigen (anti-HBs) was defined as a fourfold rise in levels to
> or = 20 mIU/mL that was not accompanied by the presence of antibody to
hepatitis B core antigen or attributable to interim vaccination. During 10
years of follow-up, 8.2% of 1,595
vaccines had boosts in anti-HBs.
Persons with boosts did not differ significantly from those without boosts in
terms of age, gender, village, initial level of anti-HBs, or level of anti-HBs
before the boost. These results
underscore the continued exposure to HBV among vaccinees
and the continued protection against disease that the vaccine provides.
High incidence of breakthrough varicella observed in
healthy Japanese children immunized with live attenuated varicella vaccine (Oka
strain).
Takayama N, Minamitani M, Takayama M.
Department of Pediatrics, Tokyo Metropolitan Komagome Hospital, Japan.
In order to know the rate of occurrence of varicella among vaccinees
(breakthrough varicella: BV), questionnaire postcards were sent to 593 healthy
children who had received varicella vaccine (Oka strain) from March 1987 to
December 1989. The questionnaire survey was repeated once a year until January
1996. The annual attack rate from the 1st to 3rd questionnaire was
approximately 12%: however, from the 5th to 8th one it was 1-4%. To February
1996, the cumulative attack rate was 157/459 (34.2%). This rate was comparable
to that among vaccinees who had confirmed seroconversion; namely, 51/132
(38.6%). These rates are much higher than those reported by other authors. All
BV cases were clinically mild; even subjects who had received the vaccine 7
years prior to the disease showed mild symptoms. The high incidence may be
partly explained by the regional epidemiology of varicella.
The decrease in annual incidence with
time after vaccination may be due to the following reasons: some vaccinees
remained free from BV owing to reinforcement of their immunity from
subclinical infection of
varicella-zoster virus (VZV)
and others from diminution of opportunity for exposure to VZV
with increasing age. Varicella
vaccine seems to be effective in modifying the symptoms of varicella,
but not potent enough in protecting from VZV
infection.
[Study on the subclinical infection of the recipients of
measles vaccine]
[Article in Chinese]
Wu T, Wang SL, Xiang YZ.
Sanitary and Anti-epidemic Station, Zhejiang Province, Hangzhou.
Through observation to subclinical infection of the 71 children who had been
inoculated against measles 12 years ago and then exposed to natural measles
from three classes at a primary school, we have noticed: (1) Subclinical
infection did exist among the crowd who were inoculation against measles;
The rate of subclinical infection of
the three classes was between 18.5%-75.0%, with an average of 45.1%.
(2) The level of the HI Ab titer was between 1:2-1:16. The peak level was
between 1:2 and/or 1:4. So the rate of subclinical infection who had been
inoculation against measles but later exposed to natural measles would depend
on the proportion of those whose titer of HI Ab was 1:2-1:4 in the crowd. (3)
The epidemiological significance of
subclinical measles infection lies in that it can actively keep and
consolidate the level of immunity to certain extent in a crowd who had been
inoculation against measles.
Measles immunity and response to revaccination of a young
adult population in Israel.
Mendelson E, Duvdevani P, Varsano N, Lerman Y, Slepon R, Dagan R, Cohen D,
Danon Y, Shohat T.
Central Virology Laboratory, Chaim Sheba Medical Center, Tel-Hashomer, Israel.
In order to evaluate the true immune status and the effect of revaccination on
a young adult population, we collected serum samples from 289 military
recruits who were vaccinated during an outbreak in 1991. Most vaccinees, age
18-25 years, had apparently been immunized once before as infants. Sera
collected just prior to the vaccination and 14 and 28 days afterwards were
tested for measles antibodies by hemagglutination inhibition (HI) and
enzyme-linked immunosorbent assay (ELISA)-IgM. Before vaccination, 46 (15.9%)
of the subjects had no HI antibodies, (< 1:4) and 48 (16.6%) had borderline
(1:4) HI titer. Following vaccination, only ten (3.5%) remained negative and
19 (6.6%) had borderline titer. The increase in HI antibody titer was
inversely proportional to the prevaccination titer, and 159 subjects (55.0%)
showed no increase at all. The geometric mean titer (GMT) rose from 9.14 to
21.47. Among the prevaccination-negative subjects (HI < 1:4) 28 (60.9%)
reached a postvaccination titer of > or = 1:8, and eight (17.4%) reached a
titer of 1:4. Twelve (26.1%) of the negative subjects seroconverted and
developed IgM, 16 (35%) seroconverted without IgM, and 18 (39%) remained
negative and did not develop IgM. A group of eight vaccinees with
prevaccination titer of > or = 1:4 developed IgM.
Some were probably infected by the
circulating wild-type virus prior to the vaccination. Thus, a total
number of 20 of the 289 subjects studied (6.9%) had true negative preimmune
status as judged by the IgM test. However, the vaccination campaign prevented
further measles cases, apparently by increasing the population's immunity,
particularly in individuals with very low titers or without measles
antibodies.
Waning immunity and its effects on vaccination schedules.
Rouderfer V, Becker NG, Hethcote HW.
School of Statistics, La Trobe University, Bundoora, Vic, Australia.
A relatively comprehensive age-specific transmission model is used to
determine the effect of various factors on the optimal vaccination ages in
one-dose and two-dose vaccination schedules. Motivated by the situation for
measles, the model allows the duration of immunity of newborns to depend on
the level of immunity of the mother at the time of the birth and allows for
waning immunity as well as boosting of
immunity by exposure to the disease. It is found that a significant
amount of waning of disease-acquired immunity is plausible when boosting
occurs but this is not an important factor in determining optimal vaccination
schedules. On the other hand, plausible rates of loss of vaccine-induced
immunity can have a substantial effect on the optimal vaccination schedule,
particularly when there is no boosting of immunity. For two-dose schedules the
optimal vaccination ages depend significantly on the level of vaccination
coverage achieved. In the presence of plausible rates of loss of
vaccine-induced immunity for measles, it is found that the vaccination
coverage required to eradicate the disease is substantially higher than
previously suggested.
Measles, mumps, and rubella antibodies in vaccinated
Baltimore children.
King JC Jr, Lichenstein R, Feigelman S, Luna C, Permutt TJ, Patel J.
Department of Pediatrics, University of Maryland School of Medicine,
Baltimore.
OBJECTIVE--To determine quantitative measles, mumps, and rubella serum
antibody levels as a function of time since vaccination in a sample of
vaccinated Baltimore children. DESIGN--Cross-sectional serologic survey.
SETTING--Pediatric outpatient departments at the University of Maryland
Medical Center, Baltimore. PARTICIPANTS--One hundred seventy children, ranging
in age from 1.5 through 16 years, who had measles, mumps, and rubella
vaccination between ages 12 and 18 months. RESULTS--Serum antibody levels to
measles and rubella declined with increasing time since vaccination. However,
no such decline in antibody levels to mumps was observed. Children who were
vaccinated between ages 12 and 14 months did not have lower antibody levels
than children who were vaccinated at age 15 months or older. CONCLUSIONS--In
areas free from natural disease, antibody levels resultant from measles,
mumps, and rubella vaccine are likely to decline with advancing age.
Revaccination with measles, mumps, and rubella vaccine may boost falling
antibody titers.
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.
Live attenuated varicella vaccine: protection in healthy
adults compared with leukemic children. National Institute of Allergy and
Infectious Diseases Varicella Vaccine Collaborative Study Group.
Gershon AA, Steinberg SP.
Department of Pediatrics, Columbia University, College of Physicians &
Surgeons, New York City.
Protection against varicella infection was assessed in leukemic children and
healthy young adults who were immunized with live attenuated varicella
vaccine. Attack rates of breakthrough infection following household exposure
to varicella in 102 children and 26 adults were similar whether one or two
doses of vaccine had been given. The mild breakthrough illness was also
similar after one or more doses. Specific antibody titers were similar 1 year
after immunization whether individuals had received one or two doses. Humoral
and cell-mediated immunity to varicella-zoster virus (VZV) was lower in these
vaccinees than in persons who had experienced natural varicella infection.
Protection after natural infection in adult family members exposed to
varicella was superior to that in vaccinees; none developed varicella
infection. These observations suggest that immunization induces less
protection than does natural disease in leukemic children and young adults.
This may be partly due to the nature of the vaccine virus, but because
responses of adults were similar to those of leukemic children, it suggests
also that both of these groups have impaired immune responses to VZV.
Boosting of humoral
immunity after exposure to VZV
was common and was observed in healthy adults with past natural infection and
in vaccinated adults and
leukemic children.
Subclinical measles infection in vaccinated seropositive
individuals in arctic Greenland.
Pedersen IR, Mordhorst CH, Glikmann G, von Magnus H.
Institute of Medical Microbiology, University of Copenhagen, Denmark.
Measles vaccination was performed in the arctic district of Scoresbysund,
Greenland in 1968, which had never been exposed to natural measles. More than
90% of the total population was vaccinated and a 94-100% seroconversion was
obtained. During a serological survey to
examine the immunity status of the vaccinees,
it was discovered that a temporary increase in measles antibodies took place in
the majority of the population 2-4 years after the vaccination. This was not
accompanied by clinically observed measles. Most likely, it was due to an
inapparent measles infection in a population considered highly immune after
vaccination.
Plasmodium falciparum: Sporozoite boosting of immunity due to a T-cell epitope
on a sporozoite vaccine. Experimental Parasitology 64, 64-70.
The impact of a malaria sporozoite
vaccine may be enhanced if protective immunity elicited by the vaccine is
boosted by natural exposure to
sporozoites. For this to
occur, a helper T lymphocyte epitope present on the vaccine must be shared by
sporozoites. These studies show that T cells from mice immunized with
R32tet32, the Plasmodium falciparum sporozoite vaccine candidate, recognize an
epitope of less than or equal to 7 amino acids derived from the
circumsporozoite protein repeat region of R32tet32, as well as an epitope on
the tet32 fusion protein tail of R32tet32.
Exposure of R32tet32 immunized animals to P. falciparumsporozoites
elicits a significant secondary antibody response which suggests that humans
who are immunized and respond to this vaccine may be boosted by field exposure
to sporozoite
infected mosquitoes.
The combination measles, mumps, rubella and varicella
vaccine in healthy children.
Arbeter AM, Baker L, Starr SE, Plotkin SA.
A clinical trial was conducted to compare the combination measles, mumps,
rubella, varicella vaccine (MMRV) and the standard measles, mumps, rubella
vaccine and subsequent varicella vaccine (MMR + V) in 15 to 17 month old
healthy children. Both the MMRV and MMR + V schedules stimulated virtually
100% seroconversion for all component viruses. Mean antibody titers were
similar for each virus component in the two vaccine groups. Clinical
reactivity post immunization was also similar with 25-29% morbilliform rashes,
12-25% mild papulovesicular (varicella) rashes, and 12.5-18% temperature
elevations above 101 degrees F. Antibodies to measles, mumps, and rubella
viruses were persistent in 8/10 originally seronegative MMRV vaccinees and 5/5
MMR + V recipients tested. On MMRV
recipient had a household exposure to chickenpox during the year postvaccination
that resulted in a subclinical boost in varicella
antibody titer. Two children in the MMR + V group had close varicella
exposures: one developed mild varicella (20 lesions). There were no known
exposures to natural measles, mumps, or rubella. Three of four MMRV vaccinees
with low titer antibody to varicella prior to immunization had greater than
four-fold rises in antibodies. The combination measles, mumps, rubella,
varicella vaccine is an immunogenic, safe and cost effective approach to
varicella immunization of healthy children.
A long-term follow-up study on the efficacy of further
attenuated live measles vaccine, Biken CAM vaccine.
Isomura S, Morishima T, Nishikawa K, Hanada N, Rahman M, Terashima M, Kido
S, Ueda S, Takahashi M.
Antibody persistence was measured in 39 children in an open community 12-13
years after immunization against measles with further attenuated live vaccine,
Biken CAM. Serum samples of the children taken every two or three years after
vaccination had higher, lower, or the same HI antibody titers as those in
samples taken 6 weeks after vaccination.
These differences reflected a decrease
in the titer in some children and subclinical natural reinfection in others.
However, all the children still retained detectable antibody in 12 or
13 years after vaccination, indicating long-term persistence of immunity after
immunization with Biken CAM vaccine. For evaluation of the protective efficacy
of the vaccine, matched controls were studied during the same period.
Serological examination revealed that 97.5% of the controls were infected with
measles and contracted the disease. In contrast, none of the vaccinees
developed clinical infection after close contact with measles patients.
Duration of immunity after rubella vaccination: a long-term
study in Switzerland.
Just M, Just V, Berger R, Burkhardt F, Schilt U.
In Switzerland 319 of 594 young women seronegative for rubella antibody
vaccinated at 15-25 years of age against rubella with the Cendehill vaccine
strain were retested 15 years later with three tests (hemagglutination
inhibition, enzyme-linked immunosorbent assay, and a neutralization technique)
for the presence of rubella antibodies. For 307 women rubella antibodies were
still detectable by all three techniques. For nine women rubella antibodies
were demonstrable by only one or two tests. Only three vaccinees were
seronegative by all three tests. These three women also showed no booster
response after challenge with the vaccine strain.
The high percentage of women with
persistent rubella antibodies 15 years after vaccination might be explained in
part by the presence of subclinical reinfections
due to a wild rubella virus.
The need for vaccines to relieve the current global resurgence of malaria is
apparent. Immunity is specific for each species of human malaria and for each
stage in the life cycle. Once protective immunogens have been identified for
one species, the homologous molecules in other species may lead to protection.
The usefulness of a particular immunogen
will be determined, in part, by its antigenic diversity in the population and
the potential for boosting during natural infection. Successful
immunization with malarial antigens may require adjuvants to induce effective,
long-lived immunity. If different vaccines become available against each stage
in the life cycle, then the composition of a particular vaccine may be
tailored for different objectives: protection for short periods (for example,
during epidemics and for tourists), decrease in disease and death, and malaria
eradication.
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.
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