A model-based evaluation of the national immunization
programme against rubella infection and congenital rubella syndrome in The
Netherlands.
van der Heijden OG, Conyn-van Spaendonck MA, Plantinga AD, Kretzschmar ME.
National Institute of Public Health and the Environment, Department of
Infectious Diseases Epidemiology, Bilthoven, The Netherlands.
In order to improve the prevention of cases of congenital rubella syndrome in
The Netherlands, in 1987 the selective vaccination strategy against rubella
infection in girls was replaced by mass vaccination. This decision was
supported by mathematical model analyses carried out by Van Druten and De Boo.
In order to compare the predicted impact of the rubella vaccination programme
with the current available data in more detail, a similar model was built.
Although the model predicts
elimination of the rubella virus, data show that virus circulation is still
present at a higher level than expected by the model. Simulation studies
indicate that import of infection and a lower vaccine effectiveness, related
to possible asymptomatic reinfection of vaccinated people, could be sources
contributing to the present virus circulation. Even though the number
of infections is much higher than the number of reported cases of disease,
limited serosurveillance data and case notification data show that females of
childbearing age are well protected by immunization.
[Mumps vaccines: vaccination failures from an immunological
viewpoint]
[Article in German]
Hess U.
Bundesamt fur Gesundheitswesen, Bern.
The significance of mucosal and systemic immunity is illustrated with the
example of the different immune response of Poliovaccine live oral (Sabin) and
Poliovaccine inactivated parenteral (Salk).
On the occasion of rubella- and
measles-outbreaks it will be demonstrated that in vaccinated people
subclinical reinfections
may much more frequently occur than clinically manifest diseases. On
the basis of these findings one may consider the large number of parotitis
cases without complications in mumps vaccinated Swiss pupils as secondary
mucosal vaccine failures at a time, when systemic immunity still was
protective. Significance for vaccination policy and consequences for handling
of vaccines shall be briefly discussed.
The present article illustrates the extent of secondary vaccine failure after
vaccination for measles, mumps and rubella (MMR). Secondary vaccine failure
means loss of the immunity induced by vaccination to such an extent that
infection becomes possible. Serological investigations carried out with
follow-up periods of up to 16 years after vaccination for measles, 21 years
after vaccination for rubella and 12 years after vaccination for mumps reveal
that loss of antibodies occurs with the elapse of time but that the clinical
significance of this is probably very limited. Where all three types of
vaccination are concerned, secondary vaccine failure has hitherto been very
seldom. Infection with measles after secondary vaccine failure is generally
described as running a milder course.
In rare cases, rubella re-infection has resulted in infection in utero,
so that a slight risk of congenital rubella cannot be entirely excluded after
successful vaccination. No extensive systematic investigations of the
effect of revaccination have been carried out and, similarly, the optimal
interval between two or more vaccinations has not been illustrated in more
detail in the literature. Subclinical
infection is not uncommon after all three vaccines. Where measles is
concerned, immunity may possibly be regarded as a continuum which, depending
upon the antibody level, protects the individual from various degrees of
clinical disease. If wild virus can be
spread via individuals with subclinical infections, it is doubtful whether
population immunity (herd immunity), which is necessary to eliminate the three
diseases, can be attained in large populations.(ABSTRACT TRUNCATED
AT 250 WORDS)
Seroepidemiology and evaluation of passive surveillance
during 1988-1989 measles outbreak in Taiwan.
Lee MS, King CC, Jean JY, Kao CL, Wang CC, Ho MS, Chen CJ, Lee GC.
Institute of Public Health, National Taiwan University (NTU), Taipei, Republic
of China ROC.
A seroepidemiological study was carried out to explore the risk factors of a
measles outbreak that occurred among school children at a rural village (Li-Tse)
in Taiwan. Among the 1166 participants, the percentage susceptible before the
outbreak was 10.5% (122/1158) which was estimated as the sum of measles IgG-negative
(29/1158) and IgM-positive (93/1166) individuals.
Among 340 vaccinated
children, 16 (4.7%) were measles IgM-positive and 10 (2.9%) were measles IgG-negative;
therefore the vaccine failure rate was estimated to be 7.6% (26/340) and
vaccine efficacy was 79.7% (95% confidence interval [CI] : 65.0-88.5). The
most important risk factors for acquiring measles infection were the presence
of other measles cases in the family (Odds Ratio [OR] = 32.5, P = 0.002) and
the presence of more than two cases in a class (OR = 29.1, P = 0.003). The
physician reporting rate was 6.1% (4/66), and the sensitivity of passive
measles surveillance was only 4.3% (4/93) by active serosurvey.
A concomitant rubella epidemic also
amplified the inaccuracy of a passive reporting system based only on clinical
diagnosis. Five children developed measles IgM but did not experience any
symptoms, indicating that asymptomatic measles infection can occur. Our
experience has highlighted three important areas for future measles
elimination: (1) the need for serological evaluation of vaccinees,
particularly those who were born during the introduction of mass immunization;
(2) improvement in measles vaccine efficacy; and (3) further investigations on
the role of asymptomatic transmission and susceptibles who remain after mass
immunization.
Studies were conducted of experimental
challenge with rubella virus in vaccinees
whose possession of vaccine-induced antibody after vaccination had been
documented and whose antibody level had become undetectable or very low over
time. The challenge virus was the Howell strain, which had been shown
to produce typical clinical and laboratory features of rubella in susceptible
persons. The challenge of the vaccinees resulted in local viral replication in
all but one; in viremia, a primary immunologic response, and a secondary
antibody response in some; and usually
in illness without a rash or in subclinical infection. The results
emphasize the importance of continuing careful clinical and laboratory
surveillance of vaccinees for determining the persistence of vaccine-induced
immunity and of considering methods for identifying and revaccinating the
minority of vaccinees who lose such immunity.
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. NOTE: In Europe at this time, "a significant
decrease in the number of childhood rubella cases has not occurred" because
children are not routinely vaccinated against the disease.
From the article:
"For nine of these women, a significant increase in antibody levels was
observed, a finding which suggests that for at least 10% of the vaccinees a
subclinical reinfection must have occurred."
Rubella epidemic in an institution: protective value of
live rubella vaccine and serological behavior of vaccinated, revaccinated and
naturally immune groups.
Baba K, Yabuuchi H, Okuni H, Harima R, Minekawa Y, Taniuchi M, Otsuka T,
Takahashi M, Okuno Y.
A rubella epidemic occurred in an institutional population composed of 189
susceptible, 37 naturally immune, 35 previously vaccinated and 38
serologically uncharacterized children and nursing staff. The epidemic lasted
3.5 months and showed more than 5 waves. Detailed clinical and serological
examinations of these subjects were made. A rash appeared in 156 (52%) of 299
persons, including 145 (87%) of 166 unvaccinated and serologically
uncharacterized subjects, but not in the 72 immune persons. In the middle of
the 3rd wave urgent vaccination of 61 children aged 0 to 2 years of the
susceptible group reduced the rate of appearance of a rash to 11 of the
children (18%), as compared with 126 (98%) of 128 subjects in the unvaccinated
non-immune group. The epidemic only reached a 4th wave in the vaccinated
group, but it extended to a 5th wave or more in unvaccinated subjects.
None of the 35 subjects in a
previously vaccinated group developed rubella, although the rate of
subclinical reinfection in this previously vaccinated group was higher (35%)
than that in the naturally immune group (17%). Three cases of subclinical
reinfection were detected even among 6 previously revaccinated subjects.
Rubella-vaccinated students. Follow-up in a public school
system.
Schiff GM, Rauh JL, Young B, Trimble S, Rotte T, Schiff BE.
In a 7 1/2-year follow-up evaluation of the duration of
rubella-vaccine-induced immunity of students who received either HPV-77 DK-12
or Cendehill vaccine, both groups showed a continous decline in
hemagglutination-inhibition antibody from seven weeks after vaccination but a
lower decline between 4 1/2 and 7 1/2 years after vaccination. However, at 7
1/2 years only 16 students (8%) receiving the Cendehill vaccine and one
student (0.5%) receiving the HPV-77 DK-12 vaccine lacked detectable antibody.
Despite the persistence of antibody titers, there was
evidence of subclinical rubella among
both groups of vaccinated students. These results emphasize the
importance of continued evaluation of the conditions of persons receiving
rubella vaccine.
Persistence of antibody after administration of monovalent
and combined live attenuated measles, mumps, and rubella virus vaccines.
Weibel RE, Buynak EB, McLean AA, Hilleman MR.
Hemagglutination-inhibiting antibodies were retained in comparable levels
eight years after vaccination with Enders' original Edmonston and more
attenuated Moraten (Attenuvax) and Schwarz line measles vaccines. Neutralizing
antibody persisted without substantial decline in titer for at least 9.5 years
after administration of Jeryl Lynn mumps virus vaccine (Mumpsvax). Antibodies
were retained without important decline in children and adults for at least
7.5 and 7 years, respectively, after administration of HPV-77 duck-modified
rubella vaccine (Meruvax). The patterns of antibody persistence 7.5 years
after administration of combined measles-mumps-rubella (M-M-R) and
mumps-rubella (Biavax) vaccines, 6 years after administration of
measles-rubella vaccine (M-R-VAX), and 4 years after administration of
measles-mumps vaccine (M-M-VAX) were the same as for the monovalent vaccines,
indicating no alteration in the retention of immunity.
Subclinical reinfection evidenced by
increase in homologous antibody titer was observed to follow vaccination the
same as occurs after natural infection.
Various attenuated live rubella vaccines now in use are considered generally
safe and immunogenic, but to date the longest that vaccinal immunity has been
shown to endure is seven years.
Subclinical reinfection is not uncommon among vaccines, but its effect
on pregnancy and fetal development is not yet fully known. At present two mass
immunization strategies are used: vaccination of all children under 12 years
of age or protection only of females 10-14 years of age. In either case
susceptible women of childbearing age who have no detectable rubella HI
antibody are immunized as well. Such women may receive the vaccine during the
postpartum period or at any other time when they are not pregnant, but strict
precautions must always be taken to make sure they do not conceive for at
least two months thereafter.
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.
"A foolish faith in authority is the worst enemy of truth."
-- Albert Einstein, letter to a friend, 1901
"I know of no safe depository of the ultimate powers of the society but the people themselves, and if we think them not enlightened enough to exercise control with a wholesome discretion, the remedy is not to take it from them, but to inform their discretion by education."
-- Thomas Jefferson, letter to William C. Jarvis, September 28, 1820
"What's the point of vaccination if it doesn't protect you from the unvaccinated?"
-- Sandy Gottstein
"Who gets to decide what the greater good is and how many will be sacrificed to it?"
