The result offers hope for stemming the tens of millions of new infections each year
The first vaccine against chlamydia has passed its
first test in humans.
About three dozen healthy women were randomly
assigned one of two versions of a chlamydia vaccine or a placebo treatment in a
clinical trial. Both vaccine versions were shown to be safe, and both produced
an immune response not seen in the placebo group, researchers report online
August 12 in the Lancet Infectious Diseases.
“These promising results provide encouragement,â€
says pediatric infectious disease specialist Toni Darville of the University of
North Carolina School of Medicine in Chapel Hill, who coauthored a commentary
accompanying the study. Chlamydia can lead to disabling, long-term
complications for women, so a vaccine against the disease could have a big
effect on public health, she says.
Chlamydia, caused by the bacterium Chlamydia trachomatis, is one of the most common sexually transmitted diseases, with around 131 million women and men newly infected worldwide each year. In the United States, it’s the most frequently reported sexually transmitted infection caused by bacteria, with at least 1.7 million cases in 2017, according to the U.S. Centers for Disease Control and Prevention. But those numbers could be low, researchers say, as infections can go unreported: The disease can produce general symptoms that may not be recognized as chlamydia, such as genital discharge or pain or no symptoms at all.
Antibiotics can clear a chlamydia infection from the
body. But left untreated, the disease can wreak reproductive havoc on women. An
infection targets the cervix, and, for about 1 in 6 women, spreads to the
uterus and fallopian tubes where it can cause pelvic inflammatory disease and
infertility.
“The percentage of women who develop these long-term
complications is relatively low,†Darville says. But the high number of
infections overall, she says, means that “a significant number of women†go on
to have chronic pelvic pain or infertility, or both.
Developing a vaccine that protects against C.
trachomatis is challenging, however, because the bacteria live a complex life
within the human body. During an infection, the microbes make their way inside
cells that line the reproductive organs. Based on studies in animals,
researchers expect that a successful vaccine needs to provoke a strong immune
response in two key ways: with antibodies, to fight the bacteria outside of
cells, and with immune system proteins and cells, such as T cells, that help to
clear bacteria from within infected cells.
In the clinical trial, immunologist and vaccine
researcher Robin Shattock of Imperial College London and colleagues tested two
versions of a chlamydia vaccine. Both versions triggered an immune response,
via antibodies and T cells, but one formulation performed better than the
other. Further testing will proceed with that version. The next step will be to
see if the vaccine prevents infection compared with a placebo, and would
involve volunteers who are at risk of infection, Shattock says.
If the vaccine passes the next clinical tests and is
approved for use, the ideal age to vaccinate girls and boys would be around 11
or 12, roughly the same as for the human papillomavirus, or HPV, vaccine (SN
Online: 4/28/17). “We are cautiously optimistic,†Shattock says. “A vaccine
against chlamydia is an important unmet need.â€
From source: https://www.sciencenews.org/article/first-chlamydia-vaccine-has-passed-major-test
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