Duration of Humoral Immunity to Common Viral and Vaccine Antigens
Ian J. Amanna, Ph.D., Nichole E. Carlson, Ph.D., and Mark K.
Slifka, Ph.D.
Original
Article
PubMed Citation
ABSTRACT
Background Maintenance of long-term antibody responses is critical
for protective immunity against many pathogens. However, the
duration of humoral immunity and the role played by memory B
cells remain poorly defined.
Methods We performed a longitudinal analysis of antibody titers
specific for viral antigens (vaccinia, measles, mumps, rubella,
varicella–zoster virus, and Epstein–Barr virus) and
nonreplicating antigens (tetanus and diphtheria) in 45 subjects
for a period of up to 26 years. In addition, we measured antigen-specific
memory B cells by means of limiting-dilution analysis, and we
compared memory B-cell frequencies to their corresponding serum
antibody levels.
Results Antiviral antibody responses were remarkably stable,
with half-lives ranging from an estimated 50 years for varicella–zoster
virus to more than 200 years for other viruses such as measles
and mumps. Antibody responses against tetanus and diphtheria
antigens waned more quickly, with estimated half-lives of 11
years and 19 years, respectively. B-cell memory was long-lived,
but there was no significant correlation between peripheral
memory B-cell numbers and antibody levels for five of the eight
antigens tested.
Conclusions These studies provide quantitative analysis of
serologic memory for multiple antigens in subjects followed
longitudinally over the course of more than one decade. In
cases in which multiple exposures or repeated vaccinations
were common, memory B-cell numbers did not correlate with
antibody titers. This finding suggests that peripheral memory
B cells and antibody-secreting plasma cells may represent
independently regulated cell populations and may play different
roles in the maintenance of protective immunity.
http://www.newsday.com:80/services/newspaper/printedition/monday/health/ny-hsvacc125457394nov12,0,3028259.story
Newsday.com
Report: Vaccine booster shots may be unnecessary
BY DELTHIA RICKS
delthia.ricks@newsday.com
November 12, 2007
Vaccines have drawn an intense spotlight in recent years,
and a study published last week raised a new question in the
debate: Do Americans overvaccinate?
Scientists writing in
the New England Journal of Medicine found that immunity lasts
far longer than previously believed, suggesting that fewer
booster shots may be warranted in adults. Still other doctors
are wondering whether new vaccine approaches would better
aid children.
At least one doctor would like to see childhood
vaccinations spread out over a longer period of time.
Dr.
Mark Slifka, an associate scientist with the Vaccine and Gene
Therapy Institute in Oregon, wanted to know how long immunity
lasts after vaccination or infection. He and his colleagues
went into the study with a lot of strong hypotheses and "expected
to see long-lived immunity following a viral infection and
relatively short-lived immunity after vaccination." Those
notions, Slifka and his team said, are the reasoning for booster
shots.
To his surprise, the research revealed that the immunity
the body marshals after vaccination with tetanus and diphtheria
lasted far longer than scientists had once believed. Immunity
that arose after certain viral infections, Slifka and collaborators
discovered, were essentially maintained for life.
Although it is important for the country to abide by vaccination
as a vital public health tool, Slifka reported in the journal,
it also is important to understand that boosters are not always
necessary.
"We also need to mention that overvaccinating the population
poses no health or safety concerns," he said, adding "it may
just be unnecessary under certain circumstances."
Dr. Len Horovitz, a pulmonary physician at Lenox Hill Hospital
in Manhattan, said while the concept of overvaccination may
sound radical and new, doctors have had the power for years
to test a person's immunity after initial vaccination. Horovitz
says he always tests students who come to see him prior to
their first year of college. If they need a booster, he gives
it.
"It is possible to prevent this phenomenon," Horovitz said,
referring to overvaccination, "by testing for antibodies."
These immune-system proteins develop in the aftermath of vaccination.
Antibodies are stimulated in the presence of a key protein
called an antigen, a protein introduced by vaccination or
infection.
The body "remembers" antigens through highly specialized,
all-knowing constituents of the immune system: B cells, whose
role is never to forget. When that memory fails, it can be
reactivated with a booster shot.
"To determine whether an MMR booster is needed," Horovitz
said of the mumps-measles-rubella shot, "antibody testing
for each antigen can be done so that an unnecessary vaccine
is not administered.
"A lot of doctors do not test to see if a patient is still
immune. When kids go to college, the university wants a kid
to get a booster. It's very possible that a booster isn't
needed - and you can test to get an answer. But there are
a lot of doctors who'll say, 'Let's just give the kid a booster.'"
Dr. Robert W. Sears, a vaccine expert and author of "The
Vaccine Book," said parents of young children also use the
term "overvaccination," but in a different way. They want
to know whether vaccinations can be spread out to avoid a
child's receiving so many shots at once.
"This is the single most important topic that I am most passionate
about," Sears said. "Parents are concerned that simultaneous
vaccines given to babies at an early age may be overwhelming
to the infants' systems."
Just as Slifka sees no need for unnecessary boosters, Sears
says it is possible to spread out vaccinations for children
and still provide them with the same level of vital immunity
to communicable diseases.
"Vaccination is definitely important," Sears said. "Vaccines
have played a tremendous role in eliminating or at least limiting
certain diseases in our population."
But he adds that spreading out the shots is far less traumatic
and does not compromise the benefit of immunization.
