Chlamydia vaccine on the horizon after early clinical trial shows promise

Professor Robin Shattock

Professor Robin Shattock

Investigator Prof Robin Shattock said: "The findings are encouraging as they show the vaccine is safe and produces the type of immune response that could potentially protect against chlamydia".

Chlamydia, caused by the bacterium Chlamydia trachomatis, presents a major global health burden - with 131 million new cases occurring annually.

For one in every six women infected with chlamydia, the infection travels up from the cervix and causes pelvic inflammatory disease.

Chlamydia is the most common bacterial STI in the world and accounts for nearly half of all sex-related infections in England.

In the trials - created to check safety and the capacity to activate the immune system - researchers separated 35 healthy women into three groups. The researchers compared two different formulations-one with added CAF01 liposomes created to aid cellular immunity and one with aluminium hydroxide known for its ability to help produce antibodies-to examine which formulation would perform better. Yet, if it isn't properly treated, it can lead to infertility and other serious complications, including ectopic pregnancy, miscarriage, stillbirth, and preterm birth. "If those trials go well we might have a vaccine that can be rolled out in around five years". Of those receiving the vaccine, 15 participants received the vaccine combined with CAF01 liposomes (CTH522:CAF01), and the other 15 received the vaccine with aluminium hydroxide (CTH522:AH).

The vaccine was administered with three injections (on day 0, 28, and 112) and two intranasal boosts (on day 126 and 140).

Both formulations of the vaccine provoked an immune response in 15 out of 15 (100%) participants, whereas no participants in the placebo group achieved an immune response. It also showed an enhanced mucosal antibody profile and more consistent cell-mediated response profile - the first providing the first line of defense against infection, the second associated with long-term immunity.

Although the vaccine provokes an immune response, whether this translates into protective immunity remains unclear.

"Given the impact of the chlamydia epidemic on women's health, reproductive health, infant health through vertical transmission, and increased susceptibility to other sexually transmitted diseases, a global unmet medical need exists for a vaccine against genital chlamydia", study author Peter Anderson from the Statens Serum Institut in Denmark said in a statement. In our trial, significantly increased concentrations of these antibodies were found in both CTH522:CAF01 and CTH522:AH-vaccinated individuals. Another five chlamydia-free women were given a placebo. The most common local reactions were injection-site pain, tenderness, and movement impairment, with 88-93% of events being reported as mild in each of the groups, lasting a median of 2-4 days in all groups.

In the latest trial, researchers compared two different formulations of the new vaccine to examine which would perform better.

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