A chlamydia vaccine developed Copenhagen-based research institute, Statens Serum Institut (SSI), has been shown to be safe to use in humans.
Chlamydia is the most common sexually transmitted bacterial infection. While there are drugs that can cure the disease, treatment offers no protection against future infections. In the UK, there are 144,000 new cases diagnosed each year – A rate of nearly 400 a day.
Screening programs have been set up in the UK and all individuals under the age of 25 are encouraged to undergo a screening test every year. The tests are free of charge but can be purchased from a pharmacy to be completed at home.
Despite drugs being available to treat the disease and screening services being widely available, the disease remains the most common sexually transmitted infection. The disease is often asymptomatic and as such, a person may only discover they are infected when complications from the disease are experienced. Complications include pelvic inflammatory disease and infertility.
A one-time vaccine could provide a lifetime of protection and could essentially lead to the eradication of the disease. SSI’s chlamydia vaccine, CTH522, is the first to be tested on humans. A phase I, double-blind, parallel, and placebo-controlled trial was conducted at University College London. The trial assessed the safety of CTH522 adjuvanted with CAF01 liposomes (CTH522:CAF01) and CTH522 adjuvanted with aluminium hydroxide (CTH522:AH). Both forms of the vaccine were given to 15 healthy women aged 18 to 45 years, with 5 women assigned to the control (saline) group.
While all women in the vaccine groups reported mild local injection-site reactions compared to none of the control group, no serious adverse reactions were experienced and anti-CTH522 IgG seroconversion was induced in 100% of the women who received the vaccine. Both vaccines induced an immunogenic response but the immunogenicity profile was better for CTH522:CAF01.
The trial was a success but it will be years before a chlamydia vaccine is made available. Further clinical trials are required to assess the effectiveness of the vaccine and determine the ideal dose. Those trials are unlikely to be completed for a couple of years so it may well be another 5 years before a vaccine is available.
Further information can be found in the paper – Safety and immunogenicity of the chlamydia vaccine candidate CTH522 adjuvanted with CAF01 liposomes or aluminium hydroxide: a first-in-human, randomised, double-blind, placebo-controlled, phase 1 trial – which was recently published in The Lancet. DOI: 10.1016/S1473-3099(19)30279-8