Chlamydia vaccine moves one step closer after the first ever scientific trial of a jab against the STI proves it is safe and provokes an immune response

• Scientists from Denmark tested two jabs on 35 healthy female volunteers 
• After five months, none of the women had suffered any serious side effects
• Most adverse events were just pain and tenderness at the site of the vaccines 

A chlamydia vaccine may be one step closer after the first ever human trial of a jab to protect against the STI has proven it is safe.

Scientists from the Statens Serum Institut in Copenhagen tested two injections on 35 healthy female volunteers.

None of the women suffered any serious side effects after five months – most of the complications included pain and tenderness at the site of the vaccines.

The jabs were also found to induce an immune response, however, whether this is strong enough to fight the STI is unclear. 

Experts stress ‘many more years of research’ is required before one of the vaccines will be available, however, ‘this trial suggests optimism for the future’.

The world’s first ever chlamydia vaccine has been found to be safe in a human trial (stock)

The World Health Organization estimates there are 131million cases of STIs around the world every year. 

Of these, chlamydia is the most common bacterial form of the infections. Around 126,000 people catch it every year in England alone.

However, as three out of four chlamydia cases cause no symptoms, there is likely many more incidences that go unreported.

Untreated infections are a ‘main driver’ of ‘disability’ among chlamydia sufferers, the researchers wrote in The Lancet Infectious Diseases.

One in six women with the STI develop pelvic inflammatory disease, which can lead to pain, ectopic pregnancies and infertility.  

Pregnant sufferers are also at risk of premature labour, still births and miscarriages. 

More than half of babies born to infected mothers ‘catch’ the STI during birth. Of which one in six develop pneumonia and half get conjunctivitis.  

Nationwide screening programmes and antibiotics have failed to ‘curb the epidemic’, the researchers wrote.

‘Thus, an effective preventive vaccine might be the best solution,’ they added.

Past studies suggest people develop partial or temporary immunity to chlamydia when infected with the STI. 

Although this encourages the production of a vaccine, a jab against the genital form of the condition has never been tested in trials. Studies against ocular chlamydia took place in the 1960s.

To put a jab to the test, 31 healthy women – who did not have the STI – received a placebo vaccine or the ‘chlamydia protein’ CTH522. 

CTH522 is found in the outer membrane of the strain Chlamydia trachomatis.

The protein was adjuvanted with either aluminium hydroxide or the liposome CAF01. Liposomes are minute sacs found in cells that are made up of fats.

Adjuvants are often added to vaccines to help promote a better immune response. 

CAFO1 aids ‘cellular immunity’, while aluminium hydroxide is ‘known for its ability’ to help produce pathogen-fighting proteins called antibodies. 

WHAT IS CHLAMYDIA?

Chlamydia is a sexually-transmitted disease.

It stems from bacteria called chlamydia trachomatis. It is passed through contact, via vaginal, anal or oral sex.

If left untreated it can damage a woman’s fallopian tubes and cause infertility. In very rare cases it can cause infertility in men too.

What are the symptoms?

The majority of people do not feel symptoms of chlamydia. Doctors recommend getting regular STD tests (urine test or swab) to detect it.

However, some do experience some side effects.

Symptoms in women: 

• Abnormal vaginal discharge
• Burning feeling when you urinate
• Pain in the eyes
• Pain in the abdomen
• Pain in the pelvis
• Pain during sex
• Vaginal bleeding 

Symptoms in men: 

• Discharge from the penis
• Burning feeling when you urinate
• Pain and swelling in one or both testicles (rarely)

How is it treated?

The infection is easily treated with antibiotics.

Doctors typically prescribe oral antibiotics, usually azithromycin (Zithromax) or doxycycline.

The women were vaccinated with the jabs at the start of the study, and again after one and four months. 

They also received a nasal version of the vaccines or placebo at four-and-a-half and five months. 

All the women agreed to use contraception or abstain from sex during the study’s duration. 

Results revealed no serious side effects occurred in any of the participants. 

The most common complications were pain, tenderness or impaired movement at the site of the injections.

This ‘mild injection site reactions’ affected all of the 15 women who had the active vaccines and three out of the five (60 per cent) who received the placebo.

The nasal vaccines did not cause significantly more side effects than the nasal placebo spray.

Seven of the 15 participants (47 per cent) who received the active nasal sprays endured sneezing, nasal congestion or an increased production of mucus.

These side effects were experienced by three out of the five participants who had the placebo spray.

As well as the jabs’ safety being proven, the active vaccines caused an immune response in all the participants. This is compared to a zero immune response in the placebo group.

The vaccine that was adjuvanted with liposomes produced 5.6 times more antibodies than the one with aluminium hydroxide.

The ‘liposome jab’ also produced more of an antibody that serves as the first-line of defense against infection. And it led to more of a response that is associated with long-term immunity. 

This vaccine will therefore be tested further in future trials, the researchers wrote.  

‘Studies of antibodies in mice have found antibodies in the vagina are the first line of defence against chlamydia infection, which suggests they are key to how effective the new vaccine may be,’ lead author Helene Juel said. 

‘In our trial, significantly increased concentrations of these antibodies were found in both vaccinated individuals. 

‘Although many more years of research are needed before this vaccine is marketed, we are planning the next stage of research’. 

Writing in a linked comment, Professor Toni Darville, of the University of South Carolina, added: ‘A vaccine for prevention of C. trachomatis infection would have enormous public health and economic impact. 

‘Although clinical vaccine testing for chlamydia is in its infancy, this trial suggests optimism for the future.’ 

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