Chlamydia, is the most common bacterial sexually transmitted infection (STI), with around 218,000 new cases in the UK in 2018, accounting for 49% of all new STI diagnoses. Worldwide it is estimated that there are 131 million new cases each year. Although it can be treated with antibiotics, around 75% of people with chlamydia do not show any signs of infection, and left untreated it can lead to infertility. Therefore there is a need for a preventive measure. The first ever clinical trial looking at a vaccine for genital chlamydia was recently published in Lancet Infectious Diseases.
The authors conducted a phase 1 RCT in 35 women, randomly assigning them to receive one of two versions of a new chlamydia vaccine (CTH522:CAF01 or CTH522:AH) (N=15 in each arm) or a saline placebo (N=5). Thirty-two women completed the study, being given an injection at the start of the study and then again 1 and 4 months later. This was followed by intranasal administrations at 4.5 and 5 months. No serious adverse events were reported, and there was no significant differences in the incidence of reactions at the injection-site (P=0.0526), or in reactions to intranasal administration (P=1.000) when comparing either vaccine to placebo. Analyses showed that both versions of the vaccine induced an immune response in all participants, compared to none in the placebo group. When comparing the two vaccines, one (CTH522:CAF01) showed more promising results including antibodies detected earlier, higher levels of IgG antibodies, an enhanced mucosal antibody profile, and a more consistent cell-mediated immune response profile. With both vaccines appearing to be safe and tolerable, further clinical trials will hopefully be forthcoming.
— Peter Chilton, Research Fellow
- Public Health England. Sexually transmitted infections and screening for chlamydia in England, 2018. Health Protection Report. 2019; 13(19).
- Abraham S, Juel HB, Bang P, et al. 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. Lancet Infect Dis. 2019.