Sexually transmitted infections (STIs) are a major public health issue in both developed and developing countries. Studies have estimated that there are over 350 million annual cases of STIs, with the rate of occurrence being higher in developing countries owing to less accessible treatment.

Efforts to control the spread of STIs worldwide include the use of early detection methods and STI testing, the use of new medications, and an emphasis on sexual education and behavioural interventions, such as the use of barrier methods.

Immunisation of at-risk populations against infectious illnesses is a highly effective method for disease control. As such, vaccines for STIs would be a remarkable addition to existing prevention strategies. When administered appropriately, vaccines are safe and important. Given the current Covid-19 pandemic, many of the suspicions and stigmas surrounding new vaccines have been fueled by misinformation and misconceptions regarding the topic.

To help clarify, we’ve written this article to give an overview of which vaccinations are currently available for STIs, and to provide some insight into future possibilities of new vaccines to combat STIs.

Which STIs currently have a vaccine?

Presently there are only two STIs for which there is a vaccine: Hepatitis B and HPV.

HPV

Human papillomavirus (HPV) is one of the most common sexually transmitted infections, and more than 200 different strains have been identified. Certain strains of HPV  are associated with a number of cancers, including those of the cervix, head, neck, and anus. Most of these infections are spread by skin-to-skin contact and target various tissues around the body, depending on the strain of HPV involved.

Fortunately, three HPV vaccines are available which prevent up to nine different forms of the virus. HPV vaccines have been made available in several countries over the past decade and have proven to be effective in reducing HPV infection and related diseases. However, more efforts are needed to increase the vaccine’s coverage in countries with less access to preventative healthcare.

HPV vaccines are highly effective in precipitating g a protective immune response, with over 98% of recipients achieving a complete antibody response (fully protected against the strains which the chosen vaccine targets) one month after completing their treatment. All vaccines were found to have an efficacy (the power to produce an intended effect) nearing 100% for the prevention of HPV-related diseases.

Which HPV strains can the HPV vaccine target?

There are currently three vaccines that target HPV types 16 and 18, which are the strains most commonly associated with HPV-related cancer. The vaccine of choice given depends upon the country in which you live.

• 9-valent HPV vaccine (Gardasil 9vHPV) - targets HPV 6, 11, 16, 18, 31, 33, 45, 52, and 58
• Quadrivalent HPV vaccine (Gardasil 4vHPV) - targets HPV 6, 11, 16, and 18
• Bivalent HPV vaccine (Cervarix 2vHPV) - targets HPV 16 and 18

The quadrivalent Gardasil vaccine has been used in the UK since 2012. Between 2021 - 2022, the vaccine of choice in the UK will be switched to Gardasil 9, to afford recipients broader protection.

Who should get the HPV vaccine?

The HPV vaccine can be given to individuals between the ages of 9 and 26 years if they have not received their first dose at an earlier age. Currently, however, the HPV vaccine is recommended for those aged 11 - 12 years.

Why is it given at such a young age? Well, HPV can be transmitted through any form of sexual contact, including touching. Therefore, individuals should be given the vaccine before they reach sexual maturity and potentially come into contact with HPV (i.e. before becoming sexually active), thus protecting them through their teenage years and beyond. 

Until the 1st of April 2018, the HPV vaccine was only available to girls. As such, men who have sex with men (MSM) have not benefited in the same way from the previous girls’ vaccine programme, and so have been left unprotected. As of April 2018, MSM up to the age of 45 years are eligible for free HPV vaccination on the NHS.

Similarly, both transgender men and transgender women are eligible for the vaccine. If trans men received their HPV vaccine as part of their school programme, then no further doses are needed. More information is found on the UK Government website.

How is the HPV vaccine administered?

The vaccine is given as an intramuscular injection (a shot injected into your muscle, typically in the upper arm or buttocks) in two doses given 6 - 24 months apart. Both doses are recommended to ensure complete immunity. Three doses are recommended if the initial dose is given between the ages of 15 - 26 years (This is because older individuals (older than 26 years) will not respond as well to two doses as younger people), if the individual is immunocompromised (more likely to contract HPV), or if the initial two doses were given less than 5 months apart (studies show that the effectiveness of the vaccine is reduced when 2 doses are given less than 5 months apart).

Although not recommended for those over the age of 26 years, the HPV vaccine can still be given to adults between the ages of 26 - 45 years who are not already vaccinated, provided they consult with their GP about their risk of contracting HPV infection and whether their risk of disease progression is greater than the risk of vaccine administration.

Where can you get the HPV vaccine?

HPV vaccines are available at GP surgeries, health clinics, school health centres, and certain health departments.

If eligible, those in the UK can receive the vaccine for free on the NHS. To see if you qualify, please visit this page for more information.

Who should not get the HPV vaccine?

Among those who should NOT get the HPV vaccine are:

• People who have a life-threatening allergy to any of the ingredients found in HPV vaccines
• People who are allergic to yeast, as Gardasil and Gardasil 9 are produced in yeast
• Pregnant individuals 

HPV vaccination is safe for those suffering from a mild cold or flu. However, if a more serious disease or illness is present, then a consultation with your GP is recommended to establish whether the vaccine is safe to take.

Hepatitis B

Caused by the hepatitis B virus (HBV), hepatitis B is transmitted by the cross-contamination of bodily fluids. This can occur through sexual intercourse, contact with infected blood (e.g. sharing needles or direct contact with an open wound), or through the placenta of an infected woman to her child. HBV is one of the leading causes of acute and chronic liver disease.

Effective vaccines against HBV were introduced in the 1980s and have proved highly successful in reducing disease burden, morbidity, and mortality in the countries where vaccination has been implemented.

Note: Though not always regarded as an STI, there is a hepatitis A vaccine available to prevent the transmission of the disease. While hepatitis A can be contracted through any kind of sexual contact. Its transmission is most often feco-oral, caused by the ingestion of water and/or food contaminated with infected feces.

Who should get the Hepatitis B vaccine?

According to the National Institute For Health and Care Excellence (NICE), the hepatitis B vaccine is recommended for:

• Infants, children, and adolescents under the age of 19 who have not been vaccinated
• People who are at risk of exposure through sexual contact (those who have a partner infected with HBV, who are sexually active and have multiple partners, or men who have sex with men)
• People who are at risk of exposure through blood contact (those who inject drugs, work in drug rehabilitation facilities, diabetics)
• Travellers to countries where hepatitis B is prevalent
• Immunocompromised individuals
• People with chronic liver disease
• People in jail or prison

How is the Hepatitis B vaccine administered?

The vaccine is part of a standard childhood (for those born on or after 1st August 2017) vaccination schedule and is given as a three-dose series over 6 months. The 6-in-1 vaccine, which vaccinates individuals against diphtheria, hepatitis B, Haemophilus influenza type B, polio, tetanus, and whooping cough, is often given to babies at 8, 12, and 16 weeks of age.

The vaccine is usually administered intramuscularly but can be given subcutaneously (into the fat) for adults and children suffering from bleeding disorders.

Where can you get the Hepatitis B vaccine?

The HBV vaccine is readily available in most community health centers, school health programs, various hospitals, and pharmacies with travel immunisation clinics.

If eligible for the vaccine, those in the UK can receive it for free on the NHS; To see if you qualify, please visit this page for more information.

Who should not get the Hepatitis B vaccine?

People who have severe or life-threatening allergic reactions to any of the ingredients found in the hepatitis B vaccine (Engerix-B or the 6-in-1) should not get the vaccine. A safety profile for the 6-in-1 vaccine can be found here. If in doubt, please discuss this with your doctor.

STI Vaccines In Development

International estimates suggest that over 1 million STIs are contracted every day around the world, bringing with them new challenges in controlling and reducing their effects--and, in turn, highlighting the importance of developing new STI vaccinations.

HIV Vaccine

HIV/AIDS remains a significant global issue, particularly in developing nations. As of now, only two potential vaccine candidates have reached phase 3 trials. Scientists have been working on developing a vaccine for over 30 years, although more research, funding, and trials are needed to successfully eradicate the HIV epidemic.

Genital Herpes Vaccine

Genital herpes is a viral infection caused by the herpes simplex virus (HSV). As infected individuals may show no symptoms at all, they tend to spread the disease unknowingly. The infection can remain in our bodies for a lifetime, causing flare-ups in the form of ulcers, rashes, or other genitourinary symptoms.

With nearly a century of research behind the formulation of a safe and effective genital herpes vaccine, only one potential candidate sponsored by Sanofi Pasteur is in pre-clinical studies. All other vaccine candidates thus far have failed to prove effective and so trials were discontinued.

As useful as it would be to have a vaccine for the herpes simplex virus, many people go on to be symptom-free over time. Its non-life-threatening nature makes it less urgent when compared to other epidemics around the globe.

No Vaccine? No Problem.

While we wait for scientists to develop these fantastic STI vaccines, there are steps that we can take today to be more proactive about our sexual health by utilising the technologies and services currently available to prevent the transmission of STIs. Improving sexual education, practising safe sex, and regular STI testing, have all proven beneficial in reducing STI transmission and the minimizing risk of developing complications when STIs are left untreated. If you prefer privacy when it comes to your sexual health, you can order one of our discreet STI testing kits which require no face-to-face contact.

That said, we should take advantage of the current STI vaccines available in the UK. The Hepatitis B and HPV vaccines are safe and effective. Tip - when we are given a chance to prevent cancer, let’s take it.

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Hassan Thwaini is a qualified Clinical Pharmacist who has completed his Master's degree at the University of Sunderland. Since then he has not only pursued community and clinical pharmacy, but has expanded to aid in humanitarian work across the less fortunate areas of the globe. Hassan is currently working as a medical writer and has successfully been published within various nutritional websites, produced unique content for his university board, and carried out research for renowned surgeons.