Further trials will be needed but the findings, published in The Lancet Infectious Diseases, could represent a vital step towards effective immunisation against the most common sexually transmitted bacterial infection worldwide, according to the researchers.
“A global unmet medical need exists for a vaccine against genital chlamydia”
National screening programmes and treatment with antibiotics have failed to reduce the incidence of chlamydia, which can cause chronic pelvic pain, infertility and increase risks of adverse outcomes during pregnancy such as miscarriage and stillbirth.
Chlamydia, which accounts for nearly half of all sexually transmitted infections (STIs) diagnosed in the UK, is also strongly linked to increased susceptibility to other STIs especially HIV and gonorrhoea.
A new vaccine tested by researchers from the UK and Denmark was the first of its kind to enter human trials – with promising results from the study funded by the European Commission and The Innovation Fund Denmark.
Researchers from Imperial College London and Statens Serum Institut in Copenhagen compared two formulations of the vaccine with a placebo jab in a randomised controlled trial among 35 healthy women.
Delivered via intramuscular injections into the arm and a booster nasal spray, both formulations appeared to be safe and provoked an immune response in all 30 women who received the vaccine that was not seen in the five who got the placebo.
However, one stood out as a front runner and researchers now plan to move this vaccine to the next phase of testing.
Although the vaccine has been shown to provoke an immune response, it is not clear whether that translates into protective immunity, according to the team, who said many more years of research would be needed before the vaccine was confirmed as effective and available for use.
The small-scale trial found all women treated with the vaccine reported mild side effects, mainly to do with slight pain and tenderness from the injection affecting only three out of the five women who got the placebo.
“This trial suggests optimism for the future”
The study authors said the development of an effective vaccine could have huge public health and cost benefits.
“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,” said one of the study authors Professor Peter Andersen.
Writing in a linked comment piece in the same journal as the research findings, Professor Toni Darville from the University of North Carolina, confirmed the results from the early trials were encouraging.
“Although clinical vaccine testing for chlamydia is in its infancy, this trial suggests optimism for the future,” she said.